A summarization of wine technology: Oenology

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OENOLOGY
A Term Paper submitted for the partial fulfillment for the degree of B.Sc. (Hons.) in
Food Science & Nutrition Management under the guidance of Ms. Damanjeet Kaur
By-
Tirna Purkait
Registration No. – 129890 of 2014-2015
Student’s ID- 14FN1005
May, 2017
Department of Food Science and Nutrition Management
J.D.Birla Institute (Affiliated to Jadavpur University)
11, Lower Rawdon Street
Kolkata-700020

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Acknowledgement
I take this opportunity to express my gratitude to everyone who has helped me and
encouraged me in the course of writing my book.
I express my gratitude to the Principal Dr. (Ms.) Deepali Singhee for providing me
with an opportunity to write a book.
I am also indebted to my guide Ms. Damanjeet Kaur, for her support and guidance
and constant encouragement for completion of this work.
I express my sincere thanks and gratitude to my teachers for guiding me with their
stimulating discussions and invaluable suggestions without which the book would not
have fallen of its present shape.
Finally, no words of gratitude can express my indebtedness to my family specially my
parents, who has always been my guiding spirit, and friends for encouraging me.
Tirna Purkait

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INDEX
Chapter Page No.
Chapter 1: Introduction of Oenology 7
Chapter 2: Some Information about Wine
2.1: Origin of Wine
2.2: Wine in India
2.3: Commercial Importance of Grapes and Wines
2.4: Classification of Wine
2.5: Wine Quality
9
9
14
17
18
21
Chapter 3: The Basics of Viticulture and Vinification
3.1: The Basics of Viticulture
3.2: The Basics of Vinification
22
22
25
Chapter 4: Chemical Constituents of Grapes and Wines
4.1: Water
4.2: Sugars
4.3: Pectin, Gums and Related Polysaccharides
4.4: Alcohols
4.5: Acids
4.6: Phenols
4.7: Aldehydes and Ketones
4.8: Amides
4.9: Amino Acids
4.10: Sulfur-containing Compounds
4.11: Other Compounds
4.12: Macromolecules
4.13: Dissolved Gases
4.14: Minerals
4.15: Chemical Nature of Varietal Aromas
28
29
29
29
30
31
32
33
34
34
34
35
35
36
37
37
Chapter 5: The Wine Making Process
5.1: The Basics of Wine Making Process
5.2: Making of Red Wine
5.3: Making of White Wine
40
40
47
53

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5.4: Alcoholic Fermentation
5.5: Some Common Faults and Their Causes in Wine Making
56
71
Chapter 6: Equipment and Method Used in Wine Making 75
Chapter 7: Barrel Maturation and Oak Treatment
7.1: The Influence of Barrel
7.2: Oak Treatments
82
83
84
Chapter 8: Preparation of Wine for Bottling
8.1: Clarification of Wine
8.2: Stabilization of Wine
8.3: Adjustment of the Sulfur Dioxide Level
8.4: Bottling
8.5: Closures
85
85
89
93
93
94
Chapter 9: Other Type of Wine Making
9.1: Making of Other Type of Still Wines
9.2: Making of Sparkling Wine
96
96
110
Chapter 10: Wine Assessment
10.1: Laboratory Wine Testing
10.2: Wine Tasting
104
104
107
Chapter 11: Wine and Health 113
Chapter 12: Neuroenology: How Brain Creates the Taste of Wine 120
Chapter 13: Conclusion 125
Appendices
Appendix 1: Some Wine Cocktails
Appendix 2: Glossary of Wine Terms
Bibliography
126-164
127
133
165

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LIST OF FIGURES
Figure No. Topic Page No.
1 Jar with wine residue found in the kitchen
of a Neolithic mud brick building, Hajji
Firuz Tepe, Iran
9
2 Archaeological sites of the Neolithic,
Copper Age, and early Bronze Age in
which vestiges of wine and olive growing
have been found
10
3 Entrance to the Areni-1 cave in southern
Armenia near the town of Areni- location
of the world's oldest known winery
10
4 Detail of a relief of the eastern stairs of
the Apadana, Persepolis, depicting
bringing their very famous wine to the
Persian king
11
5 Grape cultivation, winemaking, and
commerce in ancient Egypt (1500 BC)
12
6 Dionysus in a vineyard (late 6th century
BC amphora)
12
7 The Major Wine Regions of India 16
8 Wine export statistics (2002) for several
wine-producing countries. (Data from
International Organization of Vine &
Wine, 2005)
17
9 Classification of Wine 20
10 Structure of Grape Berry 22
11 Winery without Roof or Walls 26
12 Some important functional and chemical
groups in grapes and wine
28
13 Harvesting of Grapes for Winemaking 40
14 Pressing in Winemaking 41
15 Clarification of Wine 42
16 Bottling of Wine 42
17 Crushing of Grapes for Red Winemaking 43
18 Fermentation in Red Winemaking 47
19 Small Shaker for De-stemming 50
20 Yeast Growth Cycle 54

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Figure No. Topic Page No.
21 Biochemical mechanism of glycolysis 57
22 Fermentation and Respiration 60
23 Alcoholic Fermentation 62
24 Glyceropyruvic fermentation 63
25 Nitrogen Metabolism 64
26 Synthesis of Ergosterol in Yeasts 66
27 Synthesis of Fatty acids in Yeasts 68
28 Biosynthesis of Other Sub products 70
29 Horizontal Plate Press 76
30 Horizontal Pneumatic Press 76
31 Vertical Basket Press 77
32 Wine Aging In Oak Barrels In a Cellar 82
33 Some Common Fining Materials 88
34 Wine Bottling 94
35 Rosé Wine 98
36 Fortified Wines 99
37 Sparkling Wine 101
38 Health Benefits of Drinking Wine
(Source: American Association of Heart
in case of consumption of 1-2 ounce
glasses per day)
114
39 Analyze of Wine Flavour Objects.
Summary of Activation of flavor systems
related to Wine Tasting.
124
LIST OF TABLES
Table No. Topic Page No.
1 Serving Temperature of Different Wines 110

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CHAPTER 1: INTRODUCTION OF OENOLOGY
Oenology is the science and study of wine and winemaking. The English word
oenology derives from the word oinos ―wine (οἶνος) and the suffix –logia ―study of
(-λογία) from the Ancient Greek language. It is distinct from viticulture which
involves the agricultural endeavours of vine growing and of grape-harvesting. An
expert in the field of oenology is known as an oenologist.
Wine is basically an alcoholic beverage made from fermented grapes. These grapes
are generally Vitis vinifera, or a hybrid with Vitis labrusca or Vitis rupestris. Grapes
are fermented without the addition of sugars, acids, enzymes, water, or other
nutrients. Yeast consumes the sugar in the grapes and converts it to ethanol and
carbon dioxide. Different varieties of grapes and strains of yeasts produce different
styles of wine. These variations result from the complex interactions between the
biochemical development of the grape, the reactions involved in fermentation, the
terroir, and the production process. Many countries enact legal appellations intended
to define styles and qualities of wine. These typically restrict the geographical origin
and permitted varieties of grapes, as well as other aspects of wine production. There
are also wines made from fermenting other fruits or cereals, whose names often
specify their base. Wines made from plants other than grapes include rice wine and
various fruit wines such as those made from plums or cherries. Some well-known
examples are hard cider from apples, pomegranate wine, and elderberry wine.
The Philosophy of Wine Making-
Many wine connoisseurs think of it as an art, wine researchers tend to think of it as a
science. It can fall under both categories, it is a craft. The art is in finding out what
tastes "good" by doing tasting trials, blends etc. and the science comes from
determining the methods required to produce what tastes "good", what techniques
should be used to get the desired results.
The Characteristic of Good Wine-
The Ability to Please Both the Palate and the Intellect - Great wines offer
satisfaction on a hedonistic level, and also challenge and satiate the intellect. The
world offers many delicious wines that appeal to the senses, but lack profundity. The
ability to satisfy the intellect is subjective, but experts often prefer wines with
multiple dimensions, both aromatic and flavor.
The Ability to Hold the Taster's Interest - Profound wines could never be called
monochromatic or simple. They hold interest, not only providing an initial tantalizing
tease, but possessing a magnetic attraction due to their aromatic intensity and nuance-
filled layers of flavors.

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The Ability to Offer Intense Aromas and Flavors without Heaviness - In some
parts of the New World it has been easy to produce wines that are oversized, bold,
big, rich, but heavy. It has been said that Europe's finest wines have intense flavors
without heaviness. The ability to provide intensity without heaviness is a possible
strength.
The Ability to Taste Better with Each Sip - Most of the finest wines are better with
the last sip than the first, revealing more nuances and more complex aromas and
flavors as the wine unfolds.
The Ability to Improve with Age - In the past, longevity was certainly not a feature
of importance to most winemakers. However, discusses at the 2011 Wineries
Unlimited meeting, for better or worse, many consider this is an indisputable
characteristic of great wines.

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CHAPTER 2: SOME INFORMATION ABOUT WINE
2.1 ORIGIN OF WINE-
Wine has an archeological record dating back more than 7.5 thousand years. The
earliest suspected wine residues come from the early to mid-fifth millennium BC –
Hajji Firuz Tepe, in the northern Zagros Mountains of Iran.
The archaeological evidence of wine consumption has also been found at sites in
China, Georgia and Greece. The altered consciousness produced by wine has been
considered religious since its origin. Consumption of ritual wine was part of Jewish
practice since Biblical times and, as part of the Eucharist commemorating Jesus's Last
Supper, became even more essential to the Christian Church. Although Islam
nominally forbade the production or consumption of wine, during its Golden Age,
alchemists such as Geber pioneered wine's distillation for medicinal and industrial
purposes such as the production of perfume.
Wine production and consumption increased, burgeoning from the 15th century
onwards as part of European expansion. The origins of wine predate written records,
and modern archaeology is still uncertain about the details of the first cultivation of
wild grapevines. It has been hypothesized that early humans climbed trees to pick
berries, liked their sugary flavor, and then begun collecting them. After a few days
with fermentation setting in, juice at the bottom of any container would begin
producing low-alcohol wine. According to this theory, things changed around 10.000-
8000 BC with the transition from a nomadic to a sedentism style of living, which led
to agriculture and wine domestication.
Fig.1: Jar with wine residue found in the kitchen of a Neolithic mud brick building,
Hajji Firuz Tepe, Iran

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Wild grapes grow in Armenia, Georgia, Azerbaijan, the northern Levant, coastal and
southeastern Turkey, and northern Iran. The fermenting of strains of this wild Vitis
vinifera subsp. sylvestris (the ancestor of the modern wine grape, V. vinifera) would
have become easier following the development of pottery during the later Neolithic
(11,000 BC). However, the earliest evidence so far discovered dates from millennia
afterwards.
Oldest Winery Discovered-
The oldest-known winery was discovered in the "Areni-1" cave in Vayots Dzor,
Armenia. Dated to 4100 BC, the site contained a wine press, fermentation vats, jars,
and cups. Archaeologists also found Vitis vinifera seeds and vines. The seeds were
from Vitis vinifera vinifera, a grape still used to make wine. The cave remains date to
about 4000 BC - 900 years before the earliest comparable wine remains, found in
Egyptian tombs.
Fig.2: Archaeological sites of the Neolithic, Copper Age, and early Bronze Age in which
vestiges of wine and olive growing have been found
Fig.3: Entrance to the Areni-1 cave in southern Armenia near the town of Areni-
location of the world's oldest known winery

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The fame of Persian wine has been well known in Ancient times. The carvings on
Apadana Palace in Persepolis demonstrate soldiers from Achaemenid Empire subject
nations bringing gifts to the Achaemenid King, among them Armenians bringing their
famous wine to the king.
Domesticated grapes were abundant in the Near East from the beginning of the early
Bronze Age, starting in 3200 BC. There is also increasingly abundant evidence for
winemaking in Sumer and Egypt in the 3rd millennium BC.
History of Wine in Egypt-
Wine played an important role in ancient Egyptian ceremonial life. A thriving royal
winemaking industry was established in the Nile Delta following the introduction of
grape cultivation from the Levant to Egypt in 3000 BC. The industry was most likely
the result of trade between Egypt and Canaan during the early Bronze Age,
commencing from at least the 27th-century BC Third Dynasty, the beginning of the
Old Kingdom period.
Winemaking scenes on tomb walls, and the offering lists that accompanied them,
included wine that was definitely produced in the delta vineyards. By the end of the
Old Kingdom, five distinct wines, probably all produced in the Delta, constituted a
canonical set of provisions for the afterlife.
Wine in ancient Egypt was predominantly red. Due to its resemblance to blood, much
superstition surrounded wine-drinking in Egyptian culture. Shedeh, the most precious
drink in ancient Egypt, is now known to have been a red wine.
Fig.4: Detail of a relief of the eastern stairs of the Apadana, Persepolis, depicting bringing
their very famous wine to the Persian king

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Ancient Greece and Wine-
Much of modern wine culture derives from the practices of the ancient Greeks. The
vine preceded both the Minoan and Mycenaean cultures. Many of the grapes grown in
modern Greece are grown there exclusively and are similar or identical to the varieties
grown in ancient times. Indeed, the most popular modern Greek wine, strongly
aromatic white called retsina, is thought to be a carryover from the ancient practice of
lining the wine jugs with tree resin, imparting a distinct flavor to the drink. In
Homeric mythology, wine is usually served in "mixing bowls" rather than consumed
in an undiluted state. Dionysus, the Greek god of revelry and wine—frequently
referred to in the works of Homer and Aesop—was sometimes given the epithet
Acratophorus, "giver of unmixed wine".
Fig.5: Grape cultivation, winemaking, and commerce in ancient Egypt (1500 BC)
Fig.6: Dionysus in a vineyard (late 6th
century BC amphora)

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Ancient China and Wine-
The history of Chinese grape wine has been confirmed and proven to date back 9000
years (7000 BC), including the "(the earliest attested use)" of wild grapes in wine as
well as "earliest chemically confirmed alcoholic beverage in the world".
Archaeologists have discovered production from native "mountain grapes" like V.
thunbergii and V. filifolia during the 2nd and 1st millennia BC.
Ancient Rome and Wine-
The Roman Empire had an immense impact on the development of viticulture and
oenology. Wine was an integral part of the Roman diet and winemaking became a
precise business. Virtually all of the major wine-producing regions of Western Europe
today were established during the Roman Imperial era. During the Roman Empire,
social norms began to shift as the production of alcohol increases. Further evidence
suggests that widespread drunkenness and true alcoholism among the Romans began
in the first century BC and reached its height in the first century AD. Wine, perhaps
mixed with herbs and minerals, was assumed to serve medicinal purposes. During
Roman times, the upper classes might dissolve pearls in wine for better health.
Cleopatra created her own legend by promising Antony she would "drink the value of
a province" in one cup of wine, after which she drank an expensive pearl with a cup
of the beverage. The oldest surviving bottle still containing liquid wine, the Speyer
wine bottle, belonged to a Roman nobleman and it is dated at 325 or 350 AD.
New World Wine-
European grape varieties were first brought to what is now Mexico by the first
Spanish conquistadors to provide the necessities of the Catholic Holy Eucharist.
Planted at Spanish missions, one variety came to be known as the Mission grape and
is still planted today in small amounts. Succeeding waves of immigrants imported
French, Italian and German grapes, although wine from those native to the Americas
(whose flavors can be distinctly different) is also produced. Mexico became the most
important wine producer starting in the 16th century, to the extent that its output
began to affect Spanish commercial production. In this competitive climate, the
Spanish king sent an executive order to halt Mexico's production of wines and the
planting of vineyards.
In the context of wine, Australia, New Zealand, South Africa and other countries
without a wine tradition are considered New World producers. Wine production
began in the Cape Province of what is now South Africa in the 1680s as a business for
supplying ships. Australia's First Fleet (1788) brought cuttings of vines from South
Africa, although initial plantings failed and the first successful vineyards were

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established in the early 19th century. Until quite late in the 20th century, the product
of these countries was not well known outside their small export markets.
For example, Australia exported mainly to the United Kingdom; New Zealand
retained most of its wine for domestic consumption; and South Africa was often
isolated from the world market because of apartheid). However, with the increase in
mechanization and scientific advances in winemaking, these countries became known
for high-quality wine.
2.2 WINES IN INDIA-
Indian wine is wine made in India. The modern wine market in India is small; annual
per capita consumption of wine in the country is a mere 9 milliliters, approximately
1/8000th that of France. Viticulture in India has a long history dating back to the time
of the Indus Valley civilization when grapevines were believed to have been
introduced from Persia. Winemaking has existed throughout most of India's history
but was particularly encouraged during the time of the Portuguese and British
colonization of the subcontinent. Following the country's independence from the
British Empire, the Constitution of India declared that one of the government's aims
was the total prohibition of alcohol. Several states went dry and the government
encouraged vineyards to convert to table grape and raisin production. In the 1980s and
1990s, a revival in the Indian wine industry took place as international influences and
the growing middle class increased started increasing demand for the beverage. By
the turn of the 21st century, demand was increasing at a rate of 20-30% a year. The
city of Nasik in the state of Maharashtra is called the "Wine Capital of India."
Viticulture was believed to have been introduced to India by Persian traders sometime
in the 4th millennium BC. Historians believe that these early plantings were used
mostly for table grapes or grape juice rather than the production of an alcoholic
beverage. During the Vedic period of the 2nd and 1st millennia, the Aryan tribes of
the region were known for their indulgence in intoxicating drink and it seems
probable that wine was a current beverage. The religious text of the Vedas mentions
at least one alcoholic drink that may have been wine related sura which seems to have
been a type of rice wine that was fermented with honey. The first known mention of
grape-based wines was in the late 4th century BC writings of Chanakya who was the
chief minister of Emperor Chandragupta Maurya. In his writings, Chanakya
condemns the use of alcohol while chronicling the emperor and his court's frequent
indulgence of a style of grape wine known as Madhu.
In the centuries that would follow, wine became the privileged drink of the Kshatriya
or noble class while the lower caste typically drank alcohol made from wheat, barley
and millet. Under the rule of the Muslim Mughal Empire, alcohol was prohibited in
accordance to Islamic dietary laws. However, there are written reports about at least

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one Mughal ruler, Jahangir, who was fond of brandy wine. In the 16th century,
Portuguese colonists at Goa introduced port-style wine and the production of fortified
wines soon spread to other regions. Under British rule during the Victorian era,
viticulture and winemaking was strongly encouraged as a domestic source for the
British colonists. Vineyards were planted extensively through the Baramati, Kashmir
and Surat regions. In 1883 at the Calcutta International Exhibition, Indian wines were
showcased to a favorable reception.
The Indian wine industry was reaching a peak by the time the phylloxera epidemic
made its way to country and devastated its vineyards. It was a long road for the Indian
wine industry to recover from the devastation at the end of the 19th century.
Unfavorable religious and public opinion on alcohol developed and culminated in the
1950s when many of India's states prohibited alcohol. Vineyards were either uprooted
or encouraged to convert to table grape and raisin production. Some areas, like Goa,
continued to produce wine but the product was normally very sweet and highly
alcoholic. The turning point of the modern Indian wine industry occurred in early
1980s with the founding of The Tonia Group in the state of Goa. With the assistance
of French winemakers, The Tonia Group began to import Vitis vinifera grape varieties
like Cabernet Sauvignon, Chardonnay, Pinot Blanc, Pinot Noir and Ugni Blanc and
started making still and sparkling wines. Other wineries soon followed as the
emergence of India's growing middle class fueled the growth and development of the
Indian wine industry. While a large portion of the Indian subcontinent is not ideal for
viticulture, the large diversity of climate and geology does cover some areas with
suitable terroir for winemaking to thrive. The summer growing season in India tends
to be very hot and prone to monsoons. Many of India's wine regions also fall within
the tropical climate band. Vineyards are then planted at higher altitudes along slopes
and hillsides to benefit from cooler air and some protection from wind. The altitude of
India's vineyards typically range from around 660 ft. (200 m) in Karnataka, 984 ft.
(300 m) in Maharashtra, 2,600 ft. (800 m) along the slopes of the Sahyadri to 3,300 ft.
(1000 m) in Kashmir. Summertime temperature can get as hot as 113 °F (45 °C) and
wintertime lows can fall to 46 °F (8 °C). During the peak growing season between
June and August, rainfall averages 25– 60 inches (625-1,500 mm).Vineyards in India
range from the more temperate climate of the northwestern state of Punjab down to
the southern state of Tamil Nadu. Some of India's larger wine producing areas are
located in Maharashtra, Karnataka near Bangalore and Telangana near Hyderabad.
Within the Maharashtra region, vineyards are found on the Deccan Plateau and
around Baramati, Nasik, Pune, Sangli and Solapur. The high heat and humidity of the
far eastern half of the country limits viticultural activity.
The heat and humidity of India's wine region dictates many of the viticultural choices
that are made in the vineyards. Vines are often trained on bamboo and wire in a
pergola to increase canopy cover and to get the grapes off the ground where they
would be more prone to fungal diseases. The canopy protects the grapes against
sunburn and rows are spaced wide to help with aeration between the vines. Irrigation

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is essential in many of India's wine regions and since the 1980 s; drip irrigation has
been widely used. The tropical conditions often promote high yields which requires
frequent pruning throughout the year. Harvest normally takes place in February and is
usually done by hand. In the very warm wine regions of Tamil Nadu, Karnataka and
Andhra Pradesh, grapevines can produce a crop twice a year. Southern India is home
to several indigenous table grape varieties that can also be used in wine production
with Anabeshahi, Arkavati and Arkashyam being the most common. Popular non-
native grapes include the Bangalore Blue (Isabella) and Gulabi (Black Muscat). The
Turkish grape Sultana is the most widely planted grape in India, cover more than half
of the 148,000 acres planted in the country. In addition to the imported French
varieties that Chateau Indage planted, Sauvignon Blanc, Zinfandel, Chenin Blanc and
Clairette Blanche have started to establish a presence in the Indian wine industry.
Fig.7: The Major Wine Regions of India

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2.3 COMMERCIAL IMPORTANCE OF GRAPES AND WINES-
From origins, grape production has developed into the world‗s most important fresh
fruit crop. Worldwide grape production in 2002 was about 62 million metric tons.
This compares with roughly 57, 50, and 43 million metric tons for oranges, bananas,
and apples, respectively. The area planted under grape-vines in 2002 is estimated at
about 7.9 million hectares, down from a maximum of 10.2 million in the late 1970s.
Approximately 66% of the production was fermented into wine, 18.7% consumed as a
fresh fruit crop, and the remaining 7.7% dried for raisins. The use varies widely from
country to country, often depending on the physical and politico religious (wine
prohibition) dictates of the region. Despite its world importance, vines only cover
about 0.5% of agriculture land, and its produce constitute but 0.4% of global
household expenditure. Grape culture is largely restricted to regions characterized by
Mediterranean-type climates. Extension into cooler, warmer, or moister environments
is possible when local conditions modify the climate or viticultural practice
compensates for less than ideal conditions. Commercial production even occurs in
subtropical regions, where severe pruning stimulates nearly year-round vine growth.
In Europe, where 61% of the world‗s vineyards are located, about 77% of the crop is
fermented into wine. The latter percentage is slightly less for world production (71%),
owing to the predominant use of grapes as a table or raisin crop in Islamic countries.
Fig.8: Wine export statistics (2002) for several wine-producing countries. (Data from
International Organization of Vine & Wine, 2005)

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2.4 CLASSIFICATION OF WINE-
There is no generally accepted system of classifying wines. They may be grouped by
carbon dioxide or alcohol content, color, or stylistic, varietal or geographic origin.
Each has its advantages and disadvantages. For taxation purposes, wines often are
divided into three general categories: still, sparkling, and fortified – the latter two
typically being taxed at a higher rate. This division recognizes significant differences,
not only in production, but also use. In addition, classification by color provides the
purchaser with a rough indication of the wine‗s flavor intensity. Wines are initially
grouped based on alcohol concentration. This commonly is indicated by the terms
―table (alcohol contents ranging between 9 and 14% by volume) and ―fortified
(alcohol contents ranging between 17 and 22% by volume). Table wines are
subdivided into ―still and ―sparkling categories, depending on the wine‘s carbon
dioxide content.
Still Table Wines-
Most wines fall into the category of still table wines. The oldest division, based on
color, separates wines into white, red, and rosé subgroups. Not only does this have the
benefit of long acceptance, it reflects distinct differences in flavor, use, and
production methods. For example, red wines are more flavorful, typically drier, and
more astringent than white wines. In contrast, white wines are generally more acidic,
floral in nature, and come in a wide range of sweetness styles. Rosés fall in between,
being lighter than red wines, but more astringent than whites. Because most white
wines are intended to be consumed with meals, they typically are produced to possess
an acidic character. Combined with food proteins, the acidic aspect of the wine
becomes balanced and can both accentuate and harmonize with food flavors. Most
white wines are given little if any maturation in oak cooperage. Only wines with
distinct varietal aromas tend to benefit from an association with oak flavors. Those
with a sweet finish generally are intended to be consumed alone as a sipping wine, to
accompany or replace dessert. Most botrytized (late-harvest) wines and ice wines fall
into this category.
Modern red wines are almost exclusively dry. The absence of a detectable sweet taste
is consistent with their intended use as a food beverage. The bitter and astringent
compounds that characterize most red wines bind with food proteins, producing a
balance that otherwise would not develop. Occasionally, well-aged red wines are
saved for enjoyment after the meal. Their diminished tannin content obviates the need
for food to develop smoothness. Most red wines that age well are given the benefit of
some maturation in oak. One of the more common differences between red wines
depends on the consumer market for which they are intended. Wines processed for
early consumption have lighter, fruitier flavors, whereas those processed to enhance
aging potential often do so at the expense of early enjoyment and are initially

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excessively tannic. Beaujolais nouveau is a prime example of a wine designed for
early consumption.
Rosé wines are the most maligned of table wines. To achieve the light rosé color, the
juice of red grapes is often left in contact with the skins for only a short period. This
limits not only anthocyanin extraction, but also flavor uptake. In addition, rosé wines
soon lose their initial fruity character and fresh pink coloration (turning orangish).
Many rosé wines are also finished with a slight sparkle and sweet taste. This has made
many connoisseurs view rosés with disdain, considering them to possess the faults of
both white and red wines, but none of their benefits. To counter the stigma attached to
the term rosé, many North American versions are called blush wines or white
renderings of red cultivars.
Sparkling Wines-
Sparkling wines often are classified by method of production. The three principal
techniques are the traditional (champagne), transfer, and bulk (Charmat). They all
employ yeasts to generate the carbon dioxide that produces the effervescence.
Although precise, classification based on production method need not reflect
significant differences in sensory characteristics. For example, the traditional and
transfer methods typically aim to produce dry to semidry wines that accentuate
subtlety, limit varietal aroma, and possess a toasty bouquet. Sparkling wines differ
more due to duration of yeast contact and grape variety than method of production.
Although most bulk-method wines tend to be sweet and aromatic (i.e., Asti
Spumante), some are dry with subtle fragrances. Carbonated sparkling wines
(deriving their sparkle from carbon dioxide incorporated under pressure) show an
even wider range of styles. These include dry white wines, such as Vinho Verde
(historically obtaining its sparkle from malolactic fermentation); sweet sparkling red
wines, such as Lambrusco; most crackling rosés; and fruit-flavored coolers.
Fortified Wines (Dessert and Appetizer Wines) –
Some subcategories achieve their elevated alcohol contents without the addition of
distilled spirits (e.g., the sherry-like wines from Montilla, Spain). Thus, they are
technically not fortified. The alternative designation of aperitif and dessert wines also
has problems. Although most are used as aperitif or dessert wines, many table wines
are used similarly. For example, sparkling wines are often viewed as the ultimate
aperitif, whereas botrytized wines can be a numinous dessert wine. Regardless of
designation, wines in this category typically are consumed in small amounts, and are
seldom completely consumed shortly after opening. Their high alcohol content limits
microbial spoilage, and their marked flavor and resistance to oxidization often allow
them to remain stable for weeks after opening. These are desirable properties for
wines consumed in small amounts. The exceptions are Þno sherries and vintage ports.

20. 20
Both lose their distinctive properties several months after bottling, or several hours
after opening, respectively. Fortified wines are produced in a wide range of styles.
Dry or bitter-tasting forms are normally consumed as aperitifs before meals. They
stimulate the appetite and activate the release of digestive juices. Examples are Þno-
style sherries and dry vermouths. The latter are flavored with a variety of herbs and
spices. More commonly, fortified wines possess a sweet attribute. Major examples are
oloroso sherries, ports, madeiras, and marsalas. These wines are consumed after
meals, or as a dessert substitute.
Fig.9: Classification of Wine

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2.5 WINE QUALITY-
Wine quality often is defined in incredibly diverse ways. It may be evaluated in terms
of subtlety and complexity, aging potential, stylistic purity, varietal expression,
ranking by experts, or consumer acceptance. Each has its justification and limitations.
Nevertheless, the views of experts (either self-proclaimed or panels of trained tasters)
have had the greatest influence on wine-makers. Premium wine sales constitute only a
small fraction of world wine production, but have had a profound influence on the
direction of oenologic and viticultural research. Its influence has been felt all the way
down to bulk-wine production. It has also brought fine-quality wine to a broader
selection of people than ever before.
Majority of wine producers, understanding the desires of the majority of consumers is
far more lucrative than a select group of connoisseurs. Understanding how a target
group perceives quality and value-for-money is particularly important. Consumer
loyalty is often fickle. It is also uncertain whether purchase is based on opinions
expressed in questionnaires. Perceived quality is the principal driving force among
connoisseurs. For the occasional wine drinker, knowledge of geographic or varietal
origin tends to be secondary – ease of availability, price, and previous experience
being the overriding factors in selection. Pleasure on consumption is usually assessed
on subjective, highly idiosyncratic criteria. In contrast, geographic origin and
reputation strongly influence the purchases of, and presumably appreciation by, wine
connoisseurs. Historical or traditional expectations are central to the quality percepts
embodied in most appellation control laws. In addition to the purely subjective and
historical views of quality, aesthetic quality is the most highly prized attribute
possessed by premium wines. Aesthetic quality is defined similarly, and uses the same
language as artistic endeavors such as sculpture, architecture, and literature. Aspects
of esthetic quality include balance, harmony, symmetry, development, duration,
complexity, subtlety, interest, and uniqueness. Defining these terms precisely is
impossible, owing to human variability in perception. Nevertheless, balance and
harmony in wine commonly refer to a smooth taste and mouth-feel, without any
aspect interfering with the overall pleasurable sensation. Symmetry refers to the
perception of compatibility between sapid (taste and mouth-feel) and olfactory
(fragrant) sensations. Development typically refers to the changes in intensity and
aromatic character after pouring. When pleasurable, development is important in
maintaining interest. Fragrance duration is also essential to the esthetic perception of
wine quality. Complexity and subtlety are additional highly valued attributes of
fragrance and flavor. The impact of these factors on memory is probably the most
significant determinant of overall wine quality.
There is a wonderful diversity in the styles and quality of wines produced throughout
the world, promoting discussion and disagreement amongst wine lovers. The wines of
individual producers, regions and countries rise and fall in popularity according to
consumer and press and TV media perceptions of style, quality, fashion and value.

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CHAPTER 3: THE BASICS OF VITICULTURE AND
VINIFICATION
3.1 THE BASICS OF VITICULTURE-
Wine making or vinification starts with the selection of grapes. As most of the wines
are made from grapes, therefore viticulture (Science, production and study of grapes)
is an important part of it.
The harvesting of healthy, ripe grapes is the end of a successful annual vineyard cycle
and the beginning of the work in the winery. The grower and winemaker are both
aware that any deficiencies in the quality of fruit will affect not only quality but also
profitability. Although the juice of the grape is seen as the essential ingredient in the
winemaking process, other constituents also have roles of varying importance.
The Structure of the Grape Berry-
The following diagram shows structure of grape berry.
Fig.10: Structure of Grape Berry

23. 23
Stalks- Stalks contain tannins that may give a bitter taste to the wine. The winemaker
may choose to de-stem the grapes completely before they are crushed. Alternatively,
the stalks, or a small proportion of them, may be left on to increase the tannin in red
wine to give extra structure. However, if the stalks are not removed, they perform a
useful task in the pressing operation by acting as drainage channels.
Skins- Skins contain colouring matters, aroma compounds, flavour constituents and
tannins. The outside waxy layer with its whitish hue is called bloom. This contains
yeasts and bacteria. Below this we find further layers containing complex substances
called polyphenols, which can be divided into two groups:
(1) Anthocyanins (black grapes) and flavones (white grapes) give grapes their colour
and as phenolic biflavanoid compounds they form antioxidants and thus give health-
giving properties to wine.
(2) Tannins are bitter compounds that are also found in stalks and pips. They can, if
unripe or not handled correctly, give dried mouth feel on the palate. Tannin levels are
higher in red wines where more use is made of the skins and stalks in the winemaking
and with greater extraction than in white and rosé wines. Some varieties such as
Cabernet Sauvignon, Syrah and Nebbiolo contain high levels of tannins; others such
as Gamay have much lower levels.
Yeasts- Yeasts are naturally occurring micro-organisms which are essential in the
fermentation process. Yeasts attach themselves to the bloom on the grape skins. There
are two basic groups of yeast present on the skins: wild yeasts and wine yeasts. Wild
yeasts need air in which to operate. Once in contact with the grape sugars, they can
convert these sugars to alcohol, but only up to about 4% alcohol by volume (ABV), at
which point they die. Wine yeasts, of the genus Saccharomyces, then take over and
continue to work until either there is no more sugar left or an alcoholic strength of
approximately 15% has been reached, at which point they die naturally.
Pulp- The pulp or flesh contains juice. If you peel the skin of either a green or black
skinned grape, the colour of the flesh is generally the same. The actual juice of the
grape is almost colourless, with the very rare exception of a couple of varieties that
have tinted flesh. The pulp/ flesh contain water, sugars, fruit acids, proteins and
minerals.
•Sugars:
When unripe, all fruits contain a high concentration of acids and low levels of sugar.
As the fruit ripens and reaches maturity, so the balance changes, with sugar levels
rising and acidity falling. Photosynthesis is the means by which a greater part of this
change occurs. Grape sugars are mainly represented by fructose and glucose. Sucrose,
although present in the leaves and phloem tubes of the vine, has no significant
presence in the grape berry. As harvest nears, the producer can measure the rise in
sugar levels by using a refractometer.

24. 24
•Acids:
By far the most important acids found in grapes are tartaric acid and malic acid, the
latter being of a higher proportion in unripe grapes. During the ripening process,
tartaric acid then becomes the principal acid. Tartaric acid is not commonly found in
plants other than vines. Acids have an important role in wine in giving a refreshing,
mouth-watering taste and also give stability and perhaps longevity to the finished
wine. There are tiny amounts of other acids present in grapes, including acetic and
citric.
• Minerals:
Potassium is the main mineral present in the grape pulp, with a concentration of up to
2500mg/l. Of the other minerals present, none has a concentration of more than
200mg/l, but the most significant are calcium and magnesium.
Pips- Pips or seeds vary in size and shape according to grape variety. Unlike with
stalks, there is no means of separating them on reception at the winery. If crushed,
they can impart astringency to the wine due to their bitter oils and hard tannins.
The Grape Vine-
The grape variety, or blend of grape varieties, from which a wine is made is a vital
factor in determining the design and style of the wine. However, it is not the only
factor, although many a Chardonnay or Cabernet Sauvignon drinker believes
otherwise. Wines made from a single variety are referred to as varietals. The name of
the variety may be stated on the label, this concept having been introduced in Alsace
in the 1920s and promoted heavily by the Californian producers in the 1970s, has now
become commonplace. However, many wines made from a single variety do not state
the fact on the label, e.g. a bottle of Chablis AC will rarely inform that the wine is
made from Chardonnay. Many top quality wines are made from a blend of two or
more varieties, with each variety helping to make a harmonious and complex blend.
This can perhaps be compared with cooking, where every ingredient adds to taste and
balance. Examples of well -known wines made from a blend of varieties include most
red Bordeaux, which are usually made from two to five different varieties.
There are thousands of different grape varieties; the names of some, e.g. Chardonnay,
are very well known. Others are largely unknown. Some varieties are truly
international, being planted in many parts of the world. Others are found in just one
country, or even in just one region within a country. Many varieties have different
names in different countries and even pseudonyms in different regions of the same
country.

25. 25
Life Span of Vine-
Grapevines can live for over 100 years and it is generally accepted that older vines
give particularly good fruit. However, with greater age the yield decreases.
Accordingly, some producers decide to replant vineyards when the vines have reached
a certain age – perhaps 30 to 40 years or so. In areas where there are problems with
virus, a vineyard could be grubbed up when the vines are just 20 years old. In the best
vineyards, producers will often replace diseased or dying vines on an individual basis,
to retain a high average age.
3.2 THE BASICS OF VINIFICATION-
Vinification is the conversion of grape juice or other vegetable extract into wine by
fermentation. The sugars contained in the pulp of grapes are fructose and glucose.
During fermentation enzymes from yeast convert the sugars into ethyl alcohol and
carbon dioxide in approximately equal proportions and heat is liberated.
C6H12O6 → 2CH3CH2OH + 2CO2 + Heat
Additionally, tiny amounts of other products are formed during the fermentation
process, including glycerol, succinic acid, butylene glycol, acetic acid, lactic acid and
other alcohols. The winemaker has to control the fermentation process, aiming for a
wine that is flavorsome, balanced and in the style required. The business of
winemaking is fraught with potential problems, including stuck fermentations (the
premature stopping of the fermentation whilst the wine still contains unfermented
sugars), acetic spoilage, or oxidation.
The amount of sugar in must (when Grapes are pressed to release the juice, and as the
grapes are pressed whole, this soupy mixture of skins, seeds and stems is called, must)
, and the reducing sugar (glucose and fructose) in fermenting wine, can be determined
by using a density hydrometer. A number of different methods can be used to measure
density, which can be directly related to sugar content using appropriate formulae or,
more readily, prepared tables. Different countries tend to use one or other of the
methods available. The methods most commonly in use are the Baumé, Brix and
Balling methods. Throughout the vinification process it is essential to maintain
accurate records, including temperature and gravity readings.
There are important differences in the making of red, white and rosé wines. Grape
juice is almost colourless. For red wine, the colour must be extracted from the skins.
For white wines, however, some winemakers choose to have a limited skin contact
between the juice and skins because it can add a degree of complexity. Of course,
white wine can be made from black grapes, commonly practiced in the Champagne
region. Rosé wine is usually made from black grapes whose juice has been in contact

26. 26
with the skins for a limited amount of time, e.g. 12 to 18 hours. Consequently, a little
colour is leached into the juice.
Winery Location and Design-
Wineries vary from centuries old stone buildings externally of timeless appearance to
the modern practical constructions, perhaps built to the design of a specialist winery
architect. The winemaker who has inherited the ancestral château with all its low
ceilings, narrow doors and dampness may long for the blank canvas available to those
with an embryonic project. While planning a new winery, keeping the building cool is
a major consideration. In a hot climate, the building should be sited on a north–south
axis, with the shorter walls into the midday sun. It can also be beneficial not to have
windows on the western side, facing the hot afternoon sun. Adequate insulation is
required, for the ideal ambient temperature inside is no more than 20o
C (68o
F).
Pumping of must or wine over long distances should be minimized. Some winery
designers aim for gravity flow, with grapes arriving at or being hoisted to the top level
for crushing. The must or wine moves only by gravity to subsequent stages of the
winemaking process. Some wineries have been built into hillsides to facilitate the
gravity flow principle and minimize the ambient temperature. Wineries use copious
amounts of water, particularly for cleaning purposes. Although water is not normally
an ingredient in winemaking, as a general rule, for every 1 litre of wine produced 10
litres of water will be used in the winery. Adequate drainage is required throughout,
especially in the vat rooms and areas where equipment washing takes place.
Ventilation is vital. Every litre of grape juice, when fermented, produces about 40
litres of carbon dioxide. The gas is asphyxiating and consequently deaths in wineries
can occur.
Fig.11: Winery without Roof or Walls

27. 27
Winery Equipment-
Equipping or re-equipping a winery is very capital intensive, and some of the items
are used for just a few days a year.
Equipment utilized includes:
• Crusher/ De-stemmers
• Fermentation and storage vats
• Presses
• Pumps
• Fixed and moveable pipes and hoses
• Filters
• Refrigeration equipment
• Barrels, if utilized
• Bottling line, if wine is to be bottled on the property
• Laboratory equipment
• Cleaning equipment
Wine is usually fermented in vats, although barrels are sometimes used, particularly
for white wines. Traditionally, wine was made in either shallow stone tubs called
lagars, in which the grapes would be trodden, the gentlest of crushing, or in open
wooden vats. Lagars are sometimes still used in Portugal by some producers of Port
wines. Cuboid vats made of concrete or cement became very popular with producers
in the early to mid-twentieth century and many still regard these as excellent
fermentation vessels. Concrete or cement vats should be lined, for the acids in wine
can attack the material. Glazed tiles were often used for this purpose, but they are
prone to damage, and wine getting behind them would present a serious hygiene
problem. A much better lining material is epoxy resin, which is easily cleaned, and
the vats can be re-lined when necessary. Stainless steel vats are now commonplace,
but it is interesting to note that it is only from the late 1970s that they gained universal
acceptance. The great advantages of the material are easiness of cleaning, and the
ability to build in cooling systems. There are two grades of steel used for
construction: 304 grade is really only suitable for red wine fermentations, whilst the
better 316 grade, which contains molybdenum and is harder and more corrosion
resistant, is ideal for both reds and whites. Stainless steel vats may be open topped or
closed, with a sealable hatch lid and fermentation lock. Variable capacity vats are also
available and are useful even when only partly filled. These have a floating metal lid,
held in place by an inflatable plastic tire at the perimeter. Fibre glass vats are
occasionally used as a less costly alternative to stainless steel. Although in the late
twentieth century many producers replaced their wooden vats with stainless steel,
wood is again gaining popularity as a material for vat construction at some small and
medium-sized wineries. The difficulties of maintaining and sanitizing the vats are
ever present, but there is less risk of the wine being affected by reductivity.

28. 28
CHAPTER 4: CHEMICAL CONSTITUENTS OF GRAPES AND
WINES
Wine basically consists of two primary ingredients-water and ethanol. However, the
basic flavor of wine depends on additional 20 or more compounds. The subtle
differences that distinguish one varietal wine from another depend on an even larger
number of compounds.
Fig.12: Some Important Functional and Chemical Groups in Grapes and Wines

29. 29
4.1 WATER-
This acts as a predominant chemical constituent of grapes and wine, water plays a
critical role in establishing the basic characteristics of wine. For example, only
compounds at least slightly soluble in water play a significant role in wine. Water also
governs the basic flow characteristics of wine. Even the occurrence of tears in a glass
of wine is partially dependent on the properties of water. In addition, the high specific
heat of water slows the warming of wine in a glass. Water is also an essential
component in many of the chemical reactions involved in grape growth, juice
fermentation, and wine aging.
4.2 SUGARS-
The principal sugars in grapes are glucose and fructose. They often occur in roughly
equal proportions at maturity, whereas over mature grapes often have a higher
proportion of fructose. Sugars other than glucose and fructose occur, but in relatively
insignificant amounts. Sucrose is rarely found in Vitis vinifera grapes, but it may
constitute up to 10% of the sugar content in non-V. vinifera cultivars. Sucrose,
whether natural or added, is enzymatically split into glucose and fructose during
fermentation. Grape sugar content varies depending on the species, variety, maturity,
and health of the fruit. Cultivars of V. vinifera generally reach a sugar concentration
of 20% or more at maturity. Other winemaking species, such as V. labruscaand , V.
rotundifolia, seldom reach this level. Sugar commonly needs to be added to the juice
from these species to develop the 10–12% alcohol content typical of most wines.
Sugar content (total soluble solids) is measured in o
Brix. o
Brix is a good indicator of
berry sugar content at levels above 18, when sugars become the predominant soluble
solids in grapes. Grape sugar content is critical to yeast growth and metabolism.
Saccharomyces cerevisiae, the primary wine yeast, derives most of its metabolic
energy from glucose and fructose. Because S. cerevisiae has limited abilities to
ferment other substances, it is important that most grape nutrients be in the form of
glucose and fructose. Unfermented sugars are collectively termed residual sugars. In
dry wines, the residual sugar content consists primarily of pentose sugars, such as
arabinose, rhamnose, and xylose, and small amounts of unfermented glucose and
fructose. The residual sugar content of dry wine is generally less than 1.5 g/litre.
4.3 PECTIN, GUM AND RELATED POLYSACCHARIDES-
Pectin, gums, and related substances typically are mucilaginous polymers of sugar
acids that hold plant cells together. They commonly occur as complex branched
chains. Pectin is linear polymers of galacturonic acid, often possessing multiple
esterified methyl groups, and complexes to varying degrees with rhamnogalacturonan

30. 30
and chains consisting of arabinans and arabinoglactan. Gums are polymeric mixtures
of arabinose, galactose, xylose, and fructose. Being partially water-soluble, they are
extracted into the juice during crushing and pressing. Extraction is favored when
whole or crushed grapes are heated to hasten anthocyanin liberation. During
fermentation, the polysaccharides form complex colloids in the presence of alcohol
and tend to precipitate. Consequently, grape pectins, gums, and glucosans seldom
cause wine clouding or filtration problems, except with pulpy cultivars.
However, pectins can cause considerable difficulty during the pressing of slip-skin
grapes, notably V. labrusca cultivars. The addition of pectinase following crushing
significantly reduces the pectin content and their effect on pressing or filtration.
4.4 ALCOHOLS-
Alcohols are organic compounds containing one or more hydroxyl groups (-OH).
Simple alcohols contain a single hydroxyl group, whereas diols and polyols contain
two or more hydroxyl groups, respectively. Phenols are six-carbon-ring compounds
containing one or more hydroxyl groups on the phenyl ring.
Ethanol-Ethanol is indisputably the most important alcohol in wine. Although small
quantities are produced in grape cells during carbonic maceration, the primary source
of ethanol in wine is yeast fermentation. Ethanol is the principal organic by-product of
fermentation. Under standard fermentation conditions, ethanol can accumulate at up
to about 14–15%. Higher levels can be reached by the sequential addition of sugar
during fermentation. Generally, however, ethanol concentrations in wine above 14–
15% are the result of fortification. The prime factors controlling ethanol production
are sugar content, fermentation temperature, and yeast strain.
Methanol-Methanol is not a major constituent in wines. Within the usual range found
in wine (0.1–0.2 g/litre), methanol has no direct sensory effect. Of the over 160 esters
found in wine, few are associated with methanol.
Higher (Fusel) Alcohols- Alcohols with more than two carbon atoms are commonly
called higher or fusel alcohols. They may be present in healthy grapes, but seldom
occur in significant amounts. Hexanols are the major exception to this generalization.
They also donate a herbaceous odor in certain wines. Other potentially significant
higher alcohols from grapes that survive fermentation are 2-ethyl-1-hexanol, benzyl
alcohol, 2-phenylethanol, 3-octanol, and 1-octen-3-ol. However, most higher alcohols
found in wine are the by-products of yeast fermentation.
Diols, Polyols and Sugar Alcohols- The most prominent diol in wine is 2, 3-
butanediol (2, 3-butylene glycol). It has little odor and possesses a mildly bittersweet
taste. It appears to have little sensory significance in wine. By far the most prominent

31. 31
wine polyol is glycerol. In dry wine, glycerol is commonly the most abundant
compound, after water and ethanol.
It is often higher in red (10 mg/ liter) than white (7 mg/liter) wines. Sugar alcohols,
such as alditol, arabitol, erythritol, mannitol, myoinositol, and sorbitol, are commonly
found in small amounts in wine. Higher concentrations usually are the result of fungal
infection in the vineyard or bacterial growth in the wine. Sugar alcohols can be
oxidized by some acetic acid bacteria to the respective sugars.
4.5 ACIDS-
Acids are characterized by the ionization and release of hydrogen ions (H
+
) in water.
With organic compounds, this property is primarily associated with the carboxyl
group. The carboxyl group dissociates into a negatively charged carboxyl radical and
a free, positively charged hydrogen ion. Inorganic acids, such as carbonic acid,
dissociate into a negatively charged ion and one or more positively charged hydrogen
ions. The degree of ionization in wine depends primarily on the cation content
(notably potassium), the pH, and the ionizing characteristics of the particular acid. For
the majority of table wines, a range of between 5.5 and 8.5 mg/liter total acidity is
desirable. White wines are typically preferred at the higher end of the scale, whereas
red wines are preferred at the lower end. A pH range of between 3.1 and 3.4 is
suitable for most white wines and between 3.3 and 3.6 for most red wines.
The principal inorganic acids in wine are carbonic and sulfurous acids. Both also
occur as dissolved gases, namely CO2 and SO2, respectively. Because they are more
important in wine as gases and do not noticeably affect wine pH or perceptible
acidity. Acidity in wine is customarily divided into two categories, volatile and fixed.
Volatile acidity refers to acids that can be readily removed by steam distillation,
whereas fixed acidity includes those that are poorly volatile. Total acidity is the
combination of both categories. Total acidity may be expressed in terms of tartaric,
malic, citric, lactic, sulfuric, or acetic acid equivalents.
Acetic Acid- Small amounts of acetic acid are produced by yeasts during
fermentation. At normal levels in wine (<300 mg/liter), acetic acid can be a desirable
flavouring, adding to the complexity of taste and odor.
Malic Acid- Malic acid may constitute about half the total acidity of grapes and wine.
Its concentration in the fruit tends to decrease as grapes mature, especially during hot
periods at the end of the season. This can lead to the production of wine with a flat
taste, and susceptible to microbial spoilage.
Lactic Acid- A small amount of lactic acid is produced by yeast cells during
fermentation. However, when lactic acid occurs as a major constituent in wine, it

32. 32
comes from the metabolic activity of bacteria. The bacteria most commonly involved
are lactic acid bacteria. They produce an enzyme that decarboxylates malic acid
directly to lactic acid. The process, called malolactic fermentation, is commonly
encouraged in red and in some white wines.
Succinic Acid- Succinic acid is one of the more common by-products of yeast
metabolism. It is resistant to microbial attack under anaerobic conditions and is
particularly stable in wine. However, the bitter-salty taste of succinic acid limits its
use for wine acidification.
Tartaric Acid- Tartaric acid is the other major grape acid, along with malic acid.
Unlike malic acid, the concentration of tartaric acid does not decline markedly during
grape ripening. In addition, tartaric acid is metabolized by few microorganisms. Thus,
it is usually the preferred acid added to increase the acidity of high pH wines.
4.6 PHENOLS-
Phenols are a class of compounds containing a phenyl ring and varying substituents.
Most of the phenols in wine are primarily derived from grape skins, stems and seeds.
Some also form during the fermentation and aging process, but these are small
compared to the amount naturally present. Phenol concentrations are varietal specific
and can be manipulated by both viticultural and oenological methods. This can
completely change the flavor and qualities of a wine. In addition, these molecules
play an important role in wine and health. Chemically, phenols are compounds
containing a cyclic benzene ring and one or more hydroxyl groups. If that sounded
like a different language, don‘t worry, it‗s not important. But what is important is
their role in wine.
Phenols are subdivided into two major groups: flavanoids and non-flavanoids. Grapes
and the subsequent wine they produce contain hundreds if not thousands of phenolic
molecules. The most noticeable characteristic of these compounds are astringency and
bitterness, particularly in red wines.
They tend to balance sweetness, as seen in this dynamic:
Sweet Taste (sugars + alcohols) <= => Acid Taste (acids) + Bitter Taste (phenols)
Phenols do not only affect taste. They also give red wine color, and act as a
preservative during the aging process. Most phenols exist in the form of tannins.
These molecules help to preserve wine by their ability to absorb oxygen. When a wine
turns brown due to oxidation, it is the phenol reaction with oxygen that causes this
color change.
The weight of a wine on the palate is largely a result of the interaction of phenols with
other compounds in a wine. Because these interactions change through aging, the

33. 33
perceptible astringency can be very different in a young red when compared with an
aged one.
Quercetin is a naturally occurring phenol in grape skins and stems that developed to
protect grapes from ultraviolet light damage. Quercetin reacts with anthocyanins to
make a deeper and more vibrant color. This process makes the color of the wine more
stable though aging.
Resveratrol is found mainly in the seeds and skins of grapes. Red wine has a
characteristically high concentration of resveratrol. This is one of the main reasons for
the beneficial effects of red wine.
Anthocyanins contribute little to the taste of wine. However, because anthocyanins
readily polymerize with tannins, they play an important role in tannin retention in and
aging. There is a close association between anthocyanins and wine color.
Anthocyanins are classified by the position of hydroxyl and methyl groups on the
second phenyl ring. Based on this, anthocyanins are separated into five groups;
cyanins, petunins, peonins, malvins and delphinins. The presence and concentration of
each of the five groups of anthocyanins is varietal specific and changes with changing
environmental conditions and viticultural practices. The proportion of five classes has
a huge impact on the color and color stability in a wine. Color and color stability are
largely affected by the number of hydroxyl and methyl groups. The number of free
hydroxyl groups is directly related to blueness; the number of methyl groups is
directly related to redness. An example of this phenomenon is malvin. It is the
primary anthocyanin in red grapes, and not surprisingly, it has the greatest degree of
methylation and thus the reddest color.
4.7 ALDEHYDES AND KETONES-
Aldehydes are carbonyl compounds distinguished by the terminal location of the
carbonyl functional group (-C=O). Ketones are related compounds with the carbonyl
group located on an internal carbon.
Grapes produce few aldehydes important in the generation of varietal aromas.
Acetaldehyde is the major wine aldehyde. It often constitutes more than 90% of its
aldehyde content. Above threshold values, it usually is considered an off-odor.
Combined with other oxidized compounds, it contributes to the fragrance of sherries
and other oxidized wines. Acetaldehyde is one of the early metabolic by-products of
fermentation. Other aldehydes, occasionally having a sensory impact on wine, are
furfural and 5- (hydroxymethyl) - 2-furaldehyde. Because furfural synthesis from
sugars is accelerated by high temperatures, furfurals primarily occur in wine heated
during processing. They add to the baked fragrance of such wines. Phenolic
aldehydes, such as cinnamaldehyde and vanillin, may accumulate in wines aged in
oak. They are degradation products of lignins found in wood cooperage.

34. 34
Few ketones are found in grapes, but those that are present usually survive
fermentation. Examples are the norisoprenoid ketones, β-damascenone, α-ionone, and
β-ionone. The intense exotic flower or rose-like scent of β-damascenone, and its low
odor threshold, indicate that it probably plays a contributing role in the aroma of
several grape varieties, including Chardonnay and Riesling. The violet–raspberry
scent generated by β-ionone, along with β-damascenone, appears to be significant in
the aroma of several red grape varieties.
Acetals are formed when an aldehyde reacts with the hydroxyl groups of two
alcohols. Acetals are typically produced during aging and distillation, potentially
contributing a vegetable-like attribute.
Esters form as condensation products between the carboxyl group of an organic acid
and the hydroxyl group of an alcohol or phenol. A prominent example is the
formation of ethyl acetate from acetic acid and ethanol.
4.8 AMIDES-
Urea is a simple nitrogen compound related to amides. It consists of two ammonia
groups attached to a common carbonyl. Urea is produced in wine as a byproduct of
arginine metabolism, and was previously added to juice to promote yeast growth. Its
presence in wine used to be considered of little significance. However, if urea is
incomplete metabolized to ammonia, it can react spontaneously with ethanol to
generate ethyl carbamate (human carcinogen).
4.9 AMINO ACIDS-
Amino acids are another class of amine derivatives. They contain a carboxyl group
attached to the amine-containing carbon. Amino acids are most important as subunits
in the biosynthesis of enzymes and other proteins. In addition, amino acids may act
both as nitrogen and energy sources for yeast metabolism. This may indirectly
generate important flavor constituents. For example, amino acids may be metabolized
to organic acids, higher alcohols, aldehydes, phenols, and lactones.
4.10 SULFUR CONTAINING COMPOUNDS-
Inorganic sulfites are the principal sulfur compounds found in grape juice and wine.
They come primarily from the deliberate addition of sulfur dioxide as an antimicrobial
or antioxidant. Even where sulfur dioxide is not added, yeast may produce between
10–30 mg /litre of sulfite.

35. 35
The metabolism of cysteine, the generation of H2S, and the presence of cysteinylated
conjugates in grapes appear to be the principal sources of thiol compounds in wine.
As a consequence of yeast metabolism, heat treatment, light exposure, or other
nonenzymatic reactions, a wide diversity of volatile sulfur-containing compounds
may be produced during fermentation, maturation, and post-bottling.
4.11 OTHER COMPOUNDS-
Pyrazines (cyclic nitrogen-containing compounds) contribute significantly to the
flavor of many natural and baked foods. They also are important to the varietal aroma
of several grape cultivars. 2-Methoxy-3- isobutylpyrazine plays a major role in the
green-pepper defect often detectable in Cabernet Sauvignon and related cultivars.
4.12 MACROMOLECULES-
Macromolecules are the polymers that constitute the structural and major regulatory
molecules of cells. These include carbohydrates, proteins, nucleic acids, and some
lipids.
Carbohydrates-The major carbohydrate polymers of plant cells are cellulose,
hemicelluloses, pectin, and starch. They function primarily as structural elements in
cell walls or as forms of energy storage. Cellulose is too insoluble to be extracted into
wine and remains with the pomace. Hemicelluloses are poorly soluble and, if
extracted, precipitate during fermentation. Pectin usually precipitate as the alcohol
content rises during fermentation or is enzymatically degraded. Occasionally, though,
they can cause clarification or filtration problems. With pulpy grape varieties, pectin
can seriously complicate pressing. Starch, the major storage carbohydrate of plants, is
not found in significant quantities in mature grapes. Grapes are atypical in using
soluble sugars as their primary storage carbohydrate. Mannans and glucans, the major
carbohydrate polymers of yeast cell walls, are either insoluble or precipitate during
fermentation. The glucans and chitins of most fungal cell walls are too insoluble to be
incorporated into wine. High-molecular weight forms can induce severe plugging
during juice or wine filtration, whereas the low-molecular-weight forms can inhibit
yeast metabolism. Yeast cell walls may be added to fermenting juice to prevent the
premature termination of fermentation.
Proteins- During ripening, the soluble protein content of grapes increases, the degree
of enrichment being cultivar dependent. After crushing, the soluble protein content
may increase by a further 50% during cold). The proteins come primarily from the
pulp. The addition of bentonite reverses this trend. During fermentation, the soluble
protein content may increase, decrease, or fluctuate markedly, depending on the
cultivar. By the end of fermentation, many proteins have precipitated with tannins,

36. 36
especially in red wines. Those that remain are highly resistant to proteolysis and low
pH values. In most wines, soluble proteins are considered undesirable, because they
may induce haze formation. In sparkling wines, however, mannoproteins help to
stabilize the effervescence.
Lipids-Both the growth and metabolic activity of yeast cells require the presence of
sterols and unsaturated fatty acids. In the presence of oxygen, yeast cells synthesize
their own lipid requirements. However, the anaerobic conditions that develop during
fermentation severely restrict the ability of yeasts to produce some lipid constituents.
Oleanolic acid (oxytriterpenic acid), a major component of grape wax, can be
incorporated and used under anaerobic conditions in the synthesis of essential yeast
sterols. The unsaturated-fatty-acid requirement also may be satisfied by linoleic and
linolenic acids released from grape cells. Both types of lipids help maintain
membrane function and enhance yeast tolerance to alcohol during and after
fermentation.
Vitamins-Vitamins encompass a series of diverse chemicals involved in the
regulation of cellular activity. They are found in small quantities in grape cells, juice,
and wine. The concentration of vitamins generally falls during fermentation and
aging. For example, ascorbic acid (vitamin C) is oxidized rapidly following crushing;
thiamine (vitamin B1) is degraded by reaction with SO2, exposure to heat, or
absorption to bentonite; and riboflavin (vitamin B2) is oxidized after exposure to light.
The only vitamin to increase notably during fermentation is p-amino benzoic acid
(PABA). Vitamins occasionally are added to juice to encourage vigorous
fermentation, diminish the use of sulfur dioxide, or reduce the likelihood of sticking.
4.13 DISSOLVED GASES-
Wines contain varying amounts of several gases. Nitrogen gas is both chemically inert
and poorly soluble in wine.
Carbon dioxide in wine comes primarily from yeast metabolism. Additional small
amounts may be generated by lactic acid bacteria. Minute amounts may arise from the
breakdown of amino acids and phenols during aging. Most of the carbon dioxide
produced by yeast action escapes during fermentation.
Before being crushed, grapes contain very low levels of oxygen. Crushing results in
the rapid uptake of about 6 ml (9 mg) O2/litre – at 20 ºC. The use of crushers
employing minimal agitation limits oxygen uptake. Slight juice aeration is preferable
as it favors complete fermentation. The oxygen allows yeasts to synthesize essential
compounds, such as unsaturated fatty acids, sterols, and nicotinic acid. It also limits
browning, by converting caftaric acid to a less-oxidizable, colorless complex with
glutathione. It also promotes the early oxidation and precipitation of other readily
oxidized phenolic compounds.

37. 37
Sulfur dioxide is a normal constituent of wine, occasionally accumulating to between
12 and 64 mg/litre as a result of yeast metabolism. Burning sulfur was used by the
ancient Egyptians, Greeks and Romans as a fumigant.
4.14 MINERALS-
Many mineral elements are found in grapes and wine. In most situations, the mineral
concentration reflects the uptake characteristics of the rootstock, accumulation by the
scion, and climatic influences on the rate of transpiration. For example, grapes in hot
climates typically have higher potassium contents than those grown in temperate or
cool climatic regions.
However, high levels of elemental sulfur may arise from fungicides applied to the
vines for disease control; elevated calcium levels may occur in wines stored in
unlined cement tanks; augmented chlorine and sodium contents may originate from
the use of ion-exchange columns; and abnormal levels of copper and iron can result
from contact with corroded winery equipment.
4.15 CHEMICAL NATURE OF VARIETAL AROMAS-
Wine is an ancient beverage and has been prized throughout time for its unique and
pleasing flavor. Wine flavor arises from a mixture of hundreds of chemical
components interacting with our sense organs, producing a neural response that is
processed in the brain and resulting in a psychophysical percept that we readily
describe as ―wine. The chemical components of wine are derived from multiple
sources; during fermentation grape flavor components are extracted into the wine and
new compounds are formed by numerous chemical and biochemical processes.
The chemical nature of wine aromas could benefit grape grower and winemaker alike
by permitting a more precise determination of a desirable harvest date. It also would
allow an assessment of how various viniculture practices influence one of the most
important determinants of wine quality, fragrance. In addition, such information could
streamline the production of new grape varieties by permitting the selection of lines
showing particular aromatic attributes. Despite its advantages, determining the
chemical nature of a varietal aroma is fraught with difficulties. The first step usually
involves the separation of grape and wine volatile components by gas
chromatography. The column may be split to divert a fraction of each compound for
sniffing, whereas the remainder undergoes physicochemical analysis. The study is
easier if the crucial compound(s) occur in a volatile form in both grapes and wine.
However, aroma compounds in grapes often occur in nonvolatile forms. They may be
released only upon crushing (e.g., C18 fatty acids into ―leaf aldehydes and alcohols),
through yeast metabolic activity (e.g., phenol into vinyl guaiacol), or during aging

38. 38
(e.g., linalool to α-terpineol). In addition, varietal aromas may originate from a
particular combination of compounds, not from variedly specific compounds.
Extraction procedures may influence the stability and, thereby, the isolation of
potentially important compounds. When compounds of probable importance are
isolated, both their identification and quantification are required. Only by comparing
the concentration in wine with its sensory threshold can its potential significance be
assessed. Because several hundred volatile compounds may occur in a wine,
multivariate analysis is often used in detecting compounds that deserve more detailed
investigation. Even with the highly precise analytical tools currently available, great
difficulty can be encountered in the detection of certain aromatic compounds (e.g.,
aldehydes bound to sulfur dioxide). However, the situation is even more demanding
when the significant compounds are labile or occur in trace amounts, for example 2-
methoxy-3-isobutylpyrazine. It is both highly labile and typically occurs in wine at
less than 35 ppt. It has a detection threshold of about 2 ppt. Based on their relative
importance in aroma production; volatile ingredients may be classified as impact,
contributing, or insignificant. Impact compounds are those that have a marked and
distinctive effect on wine fragrance. They generally give wines their varietal
distinctiveness. Although usually desirable, they may impart notoriety to wines, for
example, the foxy aroma of certain V. labrusca varieties. Contributing compounds are
considered to be those that add to the overall complexity of wine fragrance. For
example, C10 and C12 esters of unsaturated fatty acids contribute to the fruity odor of
Concord fruit and wine, but are not variedly distinctive. Ethyl esters of fatty acids as
well as acetate esters of higher alcohols add significantly to the fruity odor of most
young white wines. Contributing compounds are also important to the development of
an aged bouquet. They are equally responsible for the basic wine bouquet generated
by yeast metabolism during fermentation. The vast majority of the hundreds of
aromatic compounds found in wine fall into the insignificant category. Their
concentration is usually considerably below their threshold values. Thus, unless they
act synergistically with other compounds, they cannot influence a wine‘s aromatic
attributes. Most grape varieties do not (or are not widely acknowledged to) develop
distinctive varietal aromas. For most of those that do, unique impact compounds have
as yet to be identified. Nevertheless, there is a growing list of cultivars in which
impact compounds have been found. For example, the foxy character of some V.
labrusca cultivars has been variously ascribed to ethyl 3-mercaptopropionate, N-(N-
hydroxy-N-methyl-γ-aminobutyryl) glycin or 2-aminoacetophenone. The latter has
also been isolated from some V. vinifera wines. However, this may result from its
synthesis by some strains of S. cerevisiae or other members of the grape epiphytic
flora. The spicy character of Gewürztraminer wines has been associated with the
production of 4-vinylguaiacol (from the conversion of ferulic acid during
fermentation), in association with several terpenes. The guava-like odor occasionally
associated with Chenin Blanc and Colombard wines has been attributed to the
presence of the mercaptan, 4-methyl-4- pentan-2-one. Other variedly distinctive thiols
are 4-mercapto-4-methylpentan-2-one, 3-mercaptohexyl acetate, 4-mercapto -4-

39. 39
methylpentan-2-ol and 3-mercaptohexan-1-ol. These are formed in wine from
odorless grape precursors produced by several V. vinifera cultivars. Muscat varieties
are generally distinguished by the prominence of monoterpene alcohols and C13-
norisoprenoids in their varietal aromas.
So, it is apparent that the aroma of wine is dependent not on a particular compound
but on the profile and interactions of the multiple odor-active compounds that are
present. The potential aroma of wine is also dependent on the release of aroma
compounds from their odorless precursors during wine maturation and the
modification of volatiles due to chemical changes.

40. 40
CHAPTER 5: THE WINE MAKING PROCESS
5.1 THE BASICS OF WINE MAKING PROCESS-
Wine making has been around for thousands of years. It is not only an art but also a
science. Wine making is a natural process that requires little human intervention, but
each wine maker guides the process through different techniques. In general, there are
five basic components of the wine making process: harvesting, crushing and pressing,
fermentation, clarification, and aging and bottling. Wine makers typically follow
these five steps but add variations and deviations along the way to make their wine
unique.
Harvesting-
Harvesting is the first step in the wine making process and an important part of
ensuring delicious wine. Grapes are the only fruit that have the necessary acids, esters,
and tannins to consistently make natural and stable wine. Tannins are textural
elements that make the wine dry and add bitterness and astringency to the wine. The
moment the grapes are picked determines the acidity, sweetness, and flavor of the
wine. Determining when to harvest requires a touch of science along with old
fashioned tasting. The acidity and sweetness of the grapes should be in perfect
balance, but harvesting also heavily depends on the weather. Harvesting can be done
by hand or mechanically. Many wine makers prefer to harvest by hand because
mechanical harvesting can be tough on the grapes and the vineyard. Once the grapes
are taken to the winery, they are sorted into bunches, and rotten or under ripe grapes
are removed.
Fig.13: Harvesting of Grapes for Winemaking

41. 41
Crushing and Pressing-
After the grapes are sorted, they are ready to be de-stemmed and crushed. For many
years, men and women did this manually by stomping the grapes with their feet.
Nowadays, most wine makers perform this mechanically. Mechanical presses stomp
or trod the grapes into what is called must. Must is simply freshly pressed grape juice
that contains the skins, seeds, and solids. Mechanical pressing has brought
tremendous sanitary gain as well as increased the longevity and quality of the wine.
For white wine, the wine maker will quickly crush and press the grapes in order to
separate the juice from the skins, seeds, and solids. This is to prevent unwanted color
and tannins from leaching into the wine. Red wine, on the other hand, is left in contact
with the skins to acquire flavor, color, and additional tannins.
Fermentation-
After crushing and pressing, fermentation comes into play. Must (or juice) can begin
fermenting naturally within 6-12 hours when aided with wild yeasts in the air.
However, many wine makers intervene and add commercial cultured yeast to ensure
consistency and predict the end result.
Fermentation continues until all of the sugar is converted into alcohol and dry wine is
produced. To create a sweet wine, wine makers will sometimes stop the process
before all of the sugar is converted. Fermentation can take anywhere from 10 days to
one month or more.
Fig. 14: Pressing in Winemaking

42. 42
Clarification-
Once fermentation is complete, clarification begins. Clarification is the process in
which solids such as dead yeast cells, tannins, and proteins are removed. Wine is
transferred or ―racked‖ into a different vessel such as an oak barrel or a stainless steel
tank. Wine can then be clarified through fining or filtration. Fining occurs when
substances are added to the wine to clarify it. For example, a wine maker might add a
substance such as clay that the unwanted particles will adhere to. This will force them
to the bottom of the tank. Filtration occurs by using a filter to capture the larger
particles in the wine. The clarified wine is then racked into another vessel and
prepared for bottling or future aging.
Fig.15: Fermentation in Winemaking
Fig. 16: Clarification of Wine

43. 43
Aging and Bottling-
Aging and bottling is the final stage of the wine making process. A wine maker has
two options: bottle the wine right away or give the wine additional aging. Further
aging can be done in the bottles, stainless steel tanks, or oak barrels. Aging the wine
in oak barrels will produce a smoother, rounder, and more vanilla flavored wine. It
also increases wine‘s exposure to oxygen while it ages, which decreases tannin and
helps the wine reach its optimal fruitiness. Steel tanks are commonly used for zesty
white wines.
After aging, wines are bottled with either a cork or a screw cap, depending on the
wine maker‘s preference.
Red Wines & White Wines-
High quality, red wine grapes have colorless juice. All of the red color is in the grape
skins, and winemakers must leave the juice in contact with the skins for a
considerable time to extract the color. Red wine is made by crushing the grapes and
then fermenting the juice, the pulp, the skins and the seeds together for several days.
Near the end of sugar fermentation, a winepress is used to separate the liquid from the
solid materials. White wine is made by a differently than red wine. First the grapes are
crushed and pressed immediately to separate the juice from the solids. After pressing,
the skins, stems and seeds are discarded, and the juice is cooled to a low temperature.
Fig.17: Bottling of Wine

44. 44
Then the cold juice is allowed to settle for several hours, and the clear juice is
decanted off the residue before it is fermented. White wines are made by fermenting
clarified juice. These are the fundamental differences between making quality, red
wine and white wine. At first glance, the two winemaking processes may appear
similar because several steps are identical. Nevertheless, the steps are done in a
different sequence, and the sequence produces a large change in wine characteristics.
It has often been said that wine quality is made in the vineyard, and few experienced
winemakers disagree with this statement. The soil, climate, the viticulture and all
other aspects of the vineyard environment contribute to the quality of the wine. Even
if the winemaker does a perfect job, the quality of the starting grapes always
determines the potential quality of the wine. Grape quality is extremely important.
Many winemakers feel that when a grape growing problem develops, the difficulty
must be recognized and promptly resolved to assure fruit quality. Consequently,
professional and amateur winemakers prefer to grow their own grapes. Then they
have complete control over the vineyards.
Fermentation-
Two different fermentations occur in most red wines, and these same fermentations
are often encouraged in heavier styled white wines like Chardonnay or Sauvignon
Blanc. In addition, a variety of yeast and bacteria can grow in wine, and many of
these microorganisms can cause other fermentations.
Primary Fermentation- Conversion of the two major grape sugars (glucose and
fructose) into ethyl alcohol is called primary fermentation. Yeast in the wine produce
enzymes, and the enzymes convert the sugars into alcohol. Converting grape sugars
into alcohol is not a simple process.
Many steps are involved in this transformation, and the yeast must produce several
different enzymes.
Malolactic Fermentation- Malic acid in the grapes is converted into lactic acid
during the secondary fermentation. The necessary enzymes are produced by bacteria
rather than by yeast. Several different types of bacteria can produce malolactic (ML)
fermentation, and these bacteria are called lactic bacteria. Lactic acid is weaker than
malic acid, so malolactic fermentation reduces the overall acidity of the wine. In
addition, some byproducts produced during the malolactic fermentation can make a
positive contribution to the complexity of the wine.
Other Fermentations- Depending upon the winemaking conditions, several other
fermentations can and often do occur in wine. Some bacteria can ferment the glycerol
in the wine into lactic and acetic acids. Other types of bacteria can transform the
natural grape sugars into lactic and acetic acid. A few species of bacteria can ferment

45. 45
the tartaric acid in the wine into lactic acid, acetic acid and carbon dioxide gas.
Vinegar bacteria can convert the alcohol into acetic acid. Then the same bacteria
convert the acetic acid into water and carbon dioxide gas. These other transformations
can produce materials that detract from wine quality. Sometimes, these undesirable
fermentations can be devastating, and when such fermentations occur, wine is often
called diseased or sick.
During the fermentation phase, the primary function of the winemaker is to make sure
that the primary and secondary fermentations take place in a controlled and judicious
manner. In addition, making sure the unwanted fermentations do not occur is also
important to wine quality, so winemakers always smell and taste and measure their
wines often.
Clarification & Stabilization-
At the end of the primary fermentation, the new wine contains many spent yeast cells,
several different types of bacteria, tartrate crystals, small fragments of grape tissue,
bits of dirt, etc. All these particles interact with light that passes through the new
wine. The particles absorb or scatter the light, and they give the wine an opaque,
turbid appearance.
Gravity will slowly pull most of these particles down to the bottom of the wine
container. Then the winemaker can decant the clear wine off the sediment. The larger
sized particles may settle out in a day or two, but smaller particles may take several
weeks to fall. Some suspended material may be so small it never completely settles
out of the wine. After gravity has removed most of the impurities from the wine, the
winemaker may add a ―fining material to help the settling process. Alternatively,
most commercial winemakers would choose to filter the wine and mechanically
remove the remaining particles.
At this stage of its evolution, the wine may be clear and bright, but the wine probably
is not completely stable. In other words, the wine may not remain in a clear condition
over an extended time. Most wines contain excessive amounts of protein and
potassium hydrogen tartrate. When wine is stored under certain conditions, the protein
and the tartrate can precipitate out of the wine and produce a haze or sediment. Any
white or blush wine will probably be a total loss if either of these materials
precipitates after the wine has been bottled. Wine stability is very important to the
winemaker because of the protein and tartrate problems.
Several techniques have been developed to remove excessive amounts of protein and
tartrate from wine, and these procedures are part of the normal winemaking process.

46. 46
After the excess protein and tartrate materials have been removed, the wine will be
chemically stable. Then the winemaker can continue the winemaking process with
reasonable assurance that wine will remain clear and bright after it has been bottled.
Wine Aging-
Odours in the wine that came directly from the grapes are called wine aroma. Bouquet
is the term used for the odors in the wine produced by the winemaking process, and
winemakers use the term ―nose when referring to both the aroma and the bouquet
components.
Aroma - Wine aromas come from the grapes. Aromas do not result from the
winemaking process. Cabernet Sauvignon wine smells like Cabernet Sauvignon
because of specific aromatic materials in that particular variety of grape. The grassy
aroma, so characteristic of Sauvignon Blanc wine, is a consequence of the grape
variety, not the winemaking process.
Bouquet- The formation of wine bouquet is a more complicated process. Wine
bouquet is a result of the winemaking process. The yeast, bacteria, barrels,
winemaking procedures, etc. produce wine bouquet. Some bouquet components are
prevalent soon after the completion of fermentation, but these components decrease in
intensity with time. Other bouquet components may require several years to develop
fully.
Byproducts produced by the yeast contribute to the fresh, fruity nose so typical of
white table wines such as Gewurztraminer, Riesling and Chenin Blanc. However,
these odor components are short-lived. They often disappear in less than a year or so.
Consequently, these types of wines are best consumed when they are young, and the
nose is still fresh and fruity.
Bouquet components decrease, remain constant or increase in intensity as the wine
ages. Byproducts produced by lactic bacteria can give wines a lasting buttery
attribute. Wines stored in oak barrels slowly accumulate vanillin and other substances
from the wood. Wine acids react with alcohols to produce volatile esters, and during
bulk storage, oxidation slowly changes many wine ingredients. All these different
materials contribute to the bouquet of the wine.
After the wine is bottled, oxygen is no longer available, and a different type of aging
begins to take place. Winemakers call these transformations reduction reactions
because they take place without oxygen. Reduction aging is responsible for the
changes that produce bottle bouquet. This is the bouquet that develops after a wine
has been in the bottle for some time. As wine ages, the aroma gradually decreases,
and the wine becomes less and less varietal in character. Wine becomes more vinous
as the aroma decreases, and the bouquet increases. When wines are blind tasted, wine

47. 47
experts sometimes have trouble distinguishing old Zinfandel wines from old Cabernet
Sauvignon wines.
The winemaking process may take a few months, or it can extend for several years.
During this time many procedures and operations are performed, so winemakers keep
accurate records of the procedures used to make each wine. This record documents
the winemaking details starting from several weeks before the grapes were harvested
until the wine is bottled.
5.2 MAKING OF RED WINE-
The processing of grapes to make red wine can have various approaches can be, and
are, taken in the production of red wine and many different processes may be used.
De-stemming and crushing-
On arrival at the winery, the stalks may be removed to prevent any bitterness tainting
the juice. Following this, the grapes can be lightly crushed. The grapes are fed via a
hopper into a rotating slotted cylinder. As this rotates, the berries pass through the
slots, leaving the stalks behind – these are then expelled from the machine and can be
used for fertilizer. The grape berries are passed through a series of rollers that can be
adjusted to give the chosen pressure in order to release the juice.
For certain wines, where whole bunches are required for pressing, e.g. Beaujolais, the
grapes will not be de-stemmed or crushed. There is a growing trend amongst some red
wine makers to include at least a percentage of whole grapes in their fermentations.
Fig. 18: Crushing of Grapes for Red Winemaking

48. 48
Must preparation-
The resultant mixture of grape juice with seeds, skins and pulp (must) now has to be
prepared for fermentation. Various additions and adjustments may be undertaken.
Sulfur dioxide (SO2):
This is the winemaker‗s universal antioxidant and disinfectant, and is used at many
stages in winemaking. To prevent fermentation starting prematurely, it may be added
to inhibit the action of wild yeasts and bacteria. These organisms require oxygen for
growth, and are naturally found on grape skins. Wild yeasts (which can cause off
flavours) die when 4% alcohol is reached. Naturally occurring wine yeasts found in
the vineyard and the winery work without the action of oxygen and thus can work
even if the must is blanketed with sulfur dioxide. In many parts of the world,
winemakers now prefer to use selected cultured yeasts for greater control, reliability
and for specific flavours. It should be noted that producers often speak of wild yeast
fermentation, when refer-ring to use of the natural yeasts that come into the winery on
the grapes.
Must enrichment (chaptalisation):
In cooler climates, grapes often do not contain enough sugars to produce a balanced
wine. This may be addressed by chaptalisation – the addition of sucrose to the must or
the juice in the early stages of fermentation. It is important that only the minimum
necessary amount is added or further imbalance will be created. The practice is not
permitted in many, hotter, countries. The European Union is divided into zones
according to crude climatic conditions, and the amount, if any, of chaptalisation
allowed varies according to the zone. In some countries concentrated grape must is
used instead of sugar.
Acidification:
This may be necessary if the pH of the must is too high, that is, if the acidity is too
low. The addition of tartaric acid is the usual method employed. The addition of malic
acid is not permitted within the European Union, although it is not uncommon in
Argentina.
De-acidification:
This may be necessary if the pH of the must is too low. It is not permitted in warmer
regions of the European Union. There are a number of materials that may be used,
including calcium carbonate (CaCO3), perhaps better known as chalk, potassium
bicarbonate (KHCO3), and potassium carbonate (K2CO3). Another agent that may be
utilized is Acidex®, which is a double-salt seeded calcium carbonate designed to
reduce both tartaric and malic acids in must or wine. The product was developed in

49. 49
Germany, where the cool climate often produces grapes of high acidity. Calcium
carbonate only reduces the tartaric acid.
Yeast:
Cultured yeasts may be added, or the winemaker may simply utilize the natural yeasts
present on the skins.
Yeast nutrients:
As living organisms, yeasts need nutrients, and B group vitamins may be added to
promote their growth.
Diammonium phosphate (DAP):
This may be added, usually at a rate of 200 mg per litre of must, to help ensure that all
the sugars are fermented out and to stop the formation, during fermentation, of
hydrogen sulphide (H2S), which is most undesirable. Its use is common in New
World countries, particularly when the musts are nitrogen deficient.
Thiamine:
Thiamine (vitamin B1) may be added in the early stages of fermentation to help
increase yeast populations and prolong their life.
The yeast Brettanomyces is regarded by most as spoilage yeast and, therefore, is
generally undesirable. It needs thiamine to grow, and additions of this need to be
undertaken with caution.
Fermentation, Temperature Control and Extraction-
The process of fermentation results in the conversion of sugar by the enzymes of yeast
into alcohol and carbon dioxide.
Fermentation-
The fermentation of red wine takes place with grape solids present, in order to extract
colour from the skins. Initially the fermentation can be very tumultuous, but as more
sugar is converted, the rate slows down. In the majority of cases the fermentation is
continued until the wine is dry or off dry, and depending upon the richness of the
must, the final alcohol concentration is generally in the range 11% to 14.5% by
volume.

50. 50
Temperature control-
The fermentation process is a turbulent one and creates heat naturally. During red
winemaking, fermentation may begin at about 20o
C, but temperatures may rise to
30o
C to 32o
C. Yeast ceases to work if the temperature rises above approximately
35o
C. Therefore some form of temperature control may be necessary, especially in
warmer regions, to prevent this happening before the sugars are fully fermented. It is
only in the past few decades that wine-makers have had the equipment and ability to
be able to have real control.
Good colour extraction requires warm fermentations. However, cooler fermentations
aid the growing of yeast colonies and give higher alcoholic degrees. The warmer the
temperature, the less time the fermentation takes. Accordingly, managing the
temperature can be quite a tricky exercise. A winemaker may decide to start a vat
fairly cool, at say 20o
C, and allow it to rise naturally to around 30o
C to aid extraction.
In the latter stages, the vat may be cooled to 25o
C or so, to ensure complete
fermentation to dryness. In the cool underground cellars of regions like Burgundy, the
temperature of small vats or barrels can be self-regulating. Cooling equipment may be
required for larger vats. Wine can be pumped through heat exchangers to reduce (or
increase) temperature. Stainless steel tanks are now commonly wrapped with water or
glycol cooling jackets. Alternatively, they may be cooled by showers of cold water
running down the outside. In concrete or wooden vats a metal cooling device can be
inserted or built in.
The traditional process for red wines is for the grape mass to be fermented in open
vats. The solids and skins rise to the surface with the CO2 and create a floating cap.
This is a disadvantage because the skins need to be in contact with the juice for there
to be good extraction of colour and tannins. Also, acetic bacteria thrive in such a
warm, moist environment, risking spoilage of the juice. Consequently, during the
Fig. 19: Fermentation in Red Winemaking