1. 1
Bachelor's Degree Thesis
Research on Brewing Technology of Rose Flavour Mead
Guan Jingyi
201030710206
Academic Advisor Yang Youhui (Professor)
College College of Life Science Major Biological Science
Submission
Date
04/15/2014 Dissertation Date 05/13/2014

2. 2
Research on Brewing Technology of Rose Flavour Mead
Guan JingYi
（College of Life Science, South China Agricultural University, Guangzhou 510642,
China）
Abstract:This thesis conducts researches on the brewing technology of the rose flavour mead.
For the purpose of the research, the dried rose and natural honey are adopted as the raw
materials, to study the best leaching technical parameters of the dried rose by means of
single-factor experiment and orthogonal experiment; furthermore, to optimize the browning
inhibition technology parameters of the rose flavour mead by screening the yeast species and
conducting the single-factor experiments and orthogonal experiments related to the initial sugar
degree, PVPP and Vc dosages, etc.. The results indicate: The optimal leaching technical
parameters of dried rose include the leaching temperature of 80℃, leaching duration of 15min,
and leaching ratio of 0.65% (mass fraction); 0.03g/L Vc and 0.09g/L PVPP shall be added for
the browning inhibition; the optimal mead fermentation yeast species is Cross-Evolution;
furthermore, the optimal fermentation condition shall be achieved by adding the honey into the
dried rose leaching liquor to control the initial sugar degree at 27℃ and keep the temperature at
18℃. The final mead product shall be of 14.10° alcohol degree, 49.70g/L residual sugar and
PH 3.18. It is quite pleasant that the flavour of the rose and honey may achieve
complementarity, which makes a soft and mellow texture with the harmoniously sour and
sweet taste and the red and bright colour. Also, the browning is inhibited well.
Key Words: Mead; Rose; Browning Inhibition; Fermentation

3. 3
Contents
1 Preface.......................................................................................................................................6
1.1Honey.......................................................................................................................................6
1.2 Rose........................................................................................................................................6
1.3 Mead.......................................................................................................................................6
1.4 Mead with Natural Perfume (Rose) ......................................................................................7
1.5 Browning and Browning Inhibition.......................................................................................7
1.6 Research Contents and Significance......................................................................................8
2 Materials and Methods.............................................................................................................8
2.1 Materials ...............................................................................................................................8
2.1.1 Raw Materials.....................................................................................................................8
2.1.2Instruments and Devices......................................................................................................8
2.2 Experimental Methods ..........................................................................................................8
2.2.1 Single-factor Experiment of Dried Rose Water Leaching..................................................8
2.2.1.1 Leaching Ratio between the Dried Roses and Water.......................................................8
2.2.1.2 Leaching Temperature of Dried Roses............................................................................9
2.2.1.3 Leaching Time of Dried Roses........................................................................................9
2.2.2 Technology Optimization of Dried Rose Water Leaching.................................................9
2.2.3 Single-factor Experiment of Browning Inhibition in Dried Rose Leaching Liquor.........10
2.2.3.1 Browning Inhibition Effect of PVPP on the Dried Rose Leaching Liquor...................10
2.3.3.2 Browning Inhibition Effect of Vc on the Dried Rose Leaching Liquor........................10
2.2.4 Fermentation Technology of Browning Inhibition Rose Flavour Mead..........................11
2.2.4.1 Screening of Yeast.........................................................................................................11
2.4.4.2 Technology Optimization of Rose Flavour Mead Brewing..........................................12
3 Results and Analysis..............................................................................................................12
3.1 Single-factor Experiment Results of Dried Rose Water Leaching.....................................12
3.1.1 Leaching Ratio between the Dried Roses and Water.......................................................12

4. 4
3.1.2 Leaching Temperature of Dried Roses............................................................................13
3.1.3 Leaching Time of Dried Roses........................................................................................13
3.2 Technology Optimization of Dried Rose Water Leaching..................................................14
3.3 Browning Inhibition Effects of PVPP and Vc on the Dried Rose Leaching Liquor...........14
3.4 Screening of Optimal Yeast Species...................................................................................16
3.5 Technology Optimization of Rose Flavour Mead Brewing................................................18
3.6 Quality Indexes of Finished Mead......................................................................................21
3.6.1 Sensory Indexes...............................................................................................................21
3.6.2 Physicochemical Indexes.................................................................................................21
4 Discussion .............................................................................................................................21
4.1 Effect Factors of Dried Roses Leaching.............................................................................21
4.2 Combined Utilization of Browning Inhibitor.....................................................................22
4.3 Screening of Best Yeast......................................................................................................22
5 Conclusion.............................................................................................................................23
5.1 Research Results.................................................................................................................23
5.2 Innovative Points in the Research.......................................................................................23
5.2 Subjects Necessary for Further Research............................................................................23

5. 5
1. Preface
1.1 Honey
The honey herein refers to the sticky sweet substance processed, fermented and preserved
from the nectar, honeydew and other secrete substances gathered from the plants and brought
back to the beehive by the bees. Up to 70%～80% of the honey is composed of saccharides,
among which the glucose and the fructose account for the major part. Besides, it also contains
the polysaccharides, among which the sucrose accounts for the main part; and the maltose, the
dextrinose, the maltotriose, the kestose, etc. are the traces (Guan Liying, 2008).The honey
contains a variety of enzymes needed by the human body, such as the amylase, sucrase,
catalase, glucose transporter, etc., which can help the human body digest and fight the
oxidation and the senility (Guan Liying, 2008). The honey contains mineral substances needed
by the human body, whose contents are similar with that of the human body. This means that it
is good for the human body to assimilate and utilize, while not causing the mineral poisoning
to the body. The honey contains a plenty of amino acid and vitamins, which are quite helpful
for the human health care. Besides, the honey contains a certain amount of antimicrobial
substances, which is quite effective on the trauma care and phlogosis and sores killing (A.
Roldán, et al.,2010). The honey contains the aldehydes and alcohols and their derivatives,
which endows it with the unique honey flavour. The honey production doesn't occupy the
farmland and forest. Even more, it promotes the pollination of the agricultural crops and
enhances the agricultural development. Hence, the honey production even has been called as
"the wings of agriculture" (Guan Liying, 2008).
1.2 Rose
The rose, also called as the Rosa davurica Pall, belongs to the rozo of the Rosaceae, and is
widely planted around the world, especially the northern hemisphere. The rose contains a
plenty of the volatile oil, flavonoid, anthocyanin, etc. The rose commonly contains 0.3%-0.4%
of rose volatile oil, which helps to regulate the vital energy and alleviate the pains, promote the
blood circulation and dissolve the stasis, improve the microcirculation and so on. Thanks to its
elegant, mild and sweet aroma, it could be processed into the precious perfume or medical or

6. 6
edible products. Its content of up to 3.3% flavonoid substance helps it fight the oxidation and
senility as well as maintain beauty and youth. Besides, the anthocyanin contained in the rose is
the natural and harmless pigmentum with the efficient heat resistance and hypertonic
environment resistance, and could be used as the food dyes (Wang Duoning, 2010). What's
more, the anthocyanin can also help to fight against the free radical, protect the heart and
cerebral vessels as well as the eyesight [4]
. The rose is generally recognized as the material of
high health care value.
1.3 Mead
Human beings enjoy a very long history of mead brewing. The records of the mead are
found in the documents compiled in the Shang Dynasty, Ancient Greece and Rome of
thousands of years ago. Even more, the Compendium of Materia Medica written in Ming
Dynasty has depicted that the mead can help to keep human healthy and fit and cure the rubella
as well as the tinea corporis; and it also recorded the details of the brewing procedures
explicitly. The previous researches prove that the mead not only maintains the most of the
ingredients and utilities but also greatly improves the contests of the amino acid, vitamins and
minerals on the basis of the honey. As a result, the demand for the mead is getting larger and
larger, meanwhile, more and more meticulous in modern society. Ranging from the beverage to
the health products, from the strong wine to the mild wine, and from the compound to the
fermented wine, the variety of the mead increases; while the positioning of the mead gets more
clear (Wang Miao, et al., 2006).At the same time, even though China enjoys a huge honey
output, the mead products only account for a minor proportion of the honey reprocessing. In
China, people seldom drink the honey as a habit; hence the mead boasts of a very promising
development prospect (Zhai Wenjun, et al., 2004). Based on the existing researches, the alcohol
content of fermented mead is about 9-18%; and the comparatively optimal addition of honey is
25-66% (Paweł Sroka, et al, 2007).
1.4 Mead with Natural Spice (Roses)
The mead boasts of a high health care value and harmonious taste and is suitable for the
whole family. However, the liquor brewed from the pure honey has merely a simple flavour

7. 7
without other kinds of flavours; therefore, the addition of the perfume into the mead can meet
the increasingly higher quality requirement in the market. The flavour mead could be divided
into two kinds: one is based on the original honey liquor and added with the natural perfume,
such as the aromatic plants or the leaching liquor of the aromatic plants; the other one is based
on the original honey liquor or the honey compound wine and added with the edible perfumes
(Zhai Wenjun, et al, 2004). For the selection of the natural perfumes, according to the existing
researches, the flower added as the natural perfume can obviously help to transform the colour,
the flavour, the taste of the mead, and even enhance the consistently sluggish fermentation pace
of the mead (which may cause the bacterial infection, and finally give rise to the flavour
change, the inconsistent quality among the final products, the stuck fermentation, the increase
of the volatile acid, etc. (Paweł Sroka, et al, 2007)) (Li Li, et al., 2005). In order to meet the
unique health concept and market demands for the mead, the production by means of adding
the natural perfumes is more popular with the people, and can take a higher-end position in the
market and be more profitable. The combination of flower and wine, to some extent, has
enriched the nutrients and the health care level; and it also has developed a new mode of the
further process of the flower. Therefore, it is supposed to enjoy an abroad market prospect.
1.5 Browning and Browning Inhibition
The browning reaction is the most important factor for the storage of the fruit juice, tea,
beer, wine and other beverages in the development process. The browning reactions could be
divided into the enzymatic browning and non-enzymatic browning, between which the
enzymatic browning affects the production and storage of the abovementioned products most
greatly. The enzymatic browning gives rise to the appearance changes to the processed
products, such as, fruits, vegetables, tea, etc.; and even affects the nutritive value and flavour of
the products (Zhao Guangyuan, et al., 2006). The browning reactions of some products are
beneficial and desirable, such as, the processing of the black tea; but most of the time, the
enzymatic browning reaction causes the vast damage to value of the products. In order to
control the enzymatic reaction in the production, some drugs have been used in the production
procedure tentatively. Such as, the Poly-vinylpolypyrrolidone (PVPP), one kind of the

8. 8
absorbent that bears the proved excellent complexing absorptivity, physiological compatibility
and persistency, and has been commonly applied in the clarification and stabilization of the
wine and the beer (Li Yunfei, et al., 2012). Recently, there even comes the research that has
proved that the storage of the green tea beverage could be prolonged by applying the PVPP.
Because the PVPP could absorb the polyphenols in the beverages, whose oxidation and
complexing with the protein, natural base, amino acid, etc. however are the major cause of the
enzymatic browning; hence, the enzymatic browning could be inhibited by means of the PVPP.
Furthermore, Vitamin C (Vc) is commonly used to prevent the browning of the products. Vc
has strong reducibility and can replace the phenolic substance for the oxidation; as a result, it
protects the products. However, it is not recommended to use too much Vc, because the oxidic
Vc could affect the flavour and the appearance of the products, and it is not effective in the
case of a high content of polyphenols. Therefore, Vc has been used in the research tentatively
and collaboratively with the PVPP, and it turns out that the collaborative use could inhibit the
browning greatly (Yi Guobin, et al., 2001).
1.6 Research Contents and Significance
The research attempts to find out the optimal water leaching method of the dried rose and
the browning inhibition preservation technology for its leaching liquor by way of the
experiment. What’s more, it also researches the optimal brewing technology for the fermented
mead by adding the perfume and its leaching liquor to the honey, in order to brew the new
flavour mead products that suit the consumers best.
2. Materials and Methods
2.1 Materials
2.1.1 Raw Materials
Honey sold in the market (sugar degree of 80%) and dried rose buds sold in the market
2.1.2 Instruments and Device
Spectrophotometer, water bath, biochemical incubator, drying oven, electronic balance,
PB10-pH meter, etc.
2.2 Experimental Methods

9. 9
2.2.1 Flow Chart of Brewing Process
Rose buds (dried) → crush → water-bath leaching → strain off residue → mix and absorb
with PVPP → filter → add honey → make it acid → add nitrogen source (Ammonium
phosphate) → inoculated with yeast → fermentation → filter with aged wine
2.2.2 Single-factor Experiment of Dried Rose Water Leaching
2.2.1.1 Leaching Ratio between Dried Roses and Water
Grind the dried roses with sufficient amount to powder, grouped by different leaching
ratios (Table 1), add it to 250ml Erlenmeyer flask with 100ml 5% glucose solution, mix well
and heat the liquid under seal in water bath of 70°C for 1h, and then randomly select five
people to organize sensory evaluation group for tasting. The assessment evaluation is divided
into two parts, taste and smell, and full marks for each one are 5. The total scores are added up
by average values from five people respectively on these two indexes. Specific leaching ratio
and grouping are shown in Table 1.
Table 1 Effects of Different Leaching Ratios on Rose Leaching
No. CK 1 2 3 4
Leaching Ratio of Dried Roses (%) 0 0.3 0.5 0.7 1
Volume of 5% Glucose Solution
(mL)
100 100 100 100 100
2.2.1.2 Leaching Temperature of the Dried Roses
Based on 0.3% of leaching ratio of dried roses, find out the effects of different leaching
temperatures on rose leaching in accordance with Table 2. The remaining operations and
sensory evaluation are the same as 2.2.1.1.
Table 2 Effects of Different Temperatures on Rose Leaching
No. CK 1 2 3 4
Water Bath Temperature 23 55 70 85 97

10. 10
(°C)
Leaching Ratio (%) 0.3 0.3 0.3 0.3 0.3
2.2.1.3 Leaching Time of the Dried Roses
According to the research, the resulting temperature shall be uniformly regarded as the
heating temperature. Similarly, the resulting leaching ratio shall be uniformly regarded as the
ratio used here based on the experiment. The groups shall be divided according to the heating
time. The remaining operations and evaluation are the same as those used in the experiment
above. Specific heating time and grouping are shown in the Table 3.
Table 3 Effects of Different Leaching Time on Rose Leaching
No. CK 1 2 3 4
Leaching Time
(min)
Put in and
Pick up
Immediatel
y
15 35 55 65
Leaching Ratio
(%)
0.5 0.5 0.5 0.5 0.5
Water Bath
Temperature
(℃)
70 70 70 70 70
2.2.2 Technology Optimization of Dried Rose Water Leaching
In order to optimize the technology conditions of dried rose water leaching, the
orthogonal experiment method is adopted to explore the effects of 3 factors on the ratio
between the dried roses added and water quality, the heating temperature of water bath and the
heating time. The level of each factor is established based on the result of the single-factor
experiment. The reference index will be the total scores, which are added up by average values

11. 11
from five people respectively on the assessment of taste and smell. According to the basic steps
of the single-factor experiment, L4(23
) will be chosen in the experiment. Specific factor level is
shown in Table 4.
Table 4 Level of Factors of Dried Rose Leaching
Level Factors
Leaching
Temperature /℃(A)
Leaching Ratio (B) Leaching Time
/min(℃)
1 70（A1） 0.5（B1） 15（C1）
2 80（A2） 0.65（B2） 30（C2）
2.2.3 Single-factor Experiment of Browning Inhibition in Dried Rose Leaching Liquor
2.2.3.1 Browning Inhibition Effect of PVPP on the Dried Rose Leaching Liquor
Precisely mix enough water with PVPP suspension, and the ratio remains in 1:10.
According to the best combination and basis steps of the leaching experiment above (distilled
water instead of 5 % glucose solution), make enough leaching solution of dried roses, and then
make groups based on the different amount of PVPP. Specific operation: use the sterile gauze
for separating every leaching object, add different amount of PVPP suspension to the 250ml
beaker containing 160ml leaching liquor of dried roses, and conduct the magnetic stirring for
30min. Filter to remove PVPP after stirring and add the original leaching object again. Then
add the leaching liquor to 7 experiment tubes with the average amount of 20ml.The tubes
should be sealed at the 55℃ water bath for 7 days. Take out one tube from each group and get
the OD value under A420 measurement every day. Set another group of tubes and place it at
temperature of 4°C, compare it with the tubes that have been measured for OD value. Specific
addition amount of PVPP, temperature and grouping are shown in Table 5.
Table 5 Addition of Different Amounts of PVPP
Tube No. CK1 1 2 3 4 CK2（4℃）

12. 12
PVPP（g/L） 0 0.2 0.4 0.6 0.8 0
Temperatur
e (℃)
55 55 55 55 55 4
2.3.3.2 Browning Inhibition Effect of Vc on the Dried Rose Leaching Liquor
Precisely prepare enough 10% VC solution. According to the best combination and basis
steps of the leaching experiment above (distilled water instead of 5 % glucose solution), make
enough leaching solution, then add different amount of VC and make groups. Specific
Operation: add different amount of VC solution to 250ml beaker containing 160ml leaching
liquor of dried roses. Mix well and add the leaching liquor to 7 experiment tubes respectively
with average amount of 20ml. The tubes should be sealed at the 55℃ water bath for 7 days.
Every day, take out one tube from each group and get the OD value under A420 measurement.
Set another group of tubes and place it at temperature of 4 ℃, compare it with the tubes that
have been measured for OD value. Specific amount of Vc, temperature and grouping are
shown in Table 6.
Table 6 Addition of Different Amount of Vc
Tube No: CK1 1 2 3 4 CK2（4℃）
Vc（g/L） 0 0.1 0.3 0.5 0.7 0
Temperatur
e (℃)
55 55 55 55 55 4
2.2.4 Fermentation Technology of Browning Inhibition Rose Flavour Mead
2.2.4.1 Screening of Yeast
(1) Five kinds of killer Saccharomyces cerevisiae were adopted, namely Cross-Evolution
(the optimum temperature range of 10℃-20℃ for the production of wine),

13. 13
BM4x4(18°C-28°C), D47(15°C-20°C), QA23(10°C-32°C), and Angel Wine Yeast
(20°C-30°C). Fermentation temperature is chosen at 20°C according to their optimum
temperature range. All the initial pH values are 3.3; the initial sugar degree is 24.5°; the content
of the ammonium dihydrogen phosphate (ADP) with nutritive salt is 0.1%; the amount of yeast
inoculation is 0.4%; and the content of SO2 is 6%.After completing all the brewing in
accordance with the above progress, put together a sensory evaluation team composed of 10
people with professional wine-tasters of Level I and Level II. The assessment standards go to
the color, flavour and taste. A comprehensive ranking of each group will be made and the best
group should has the highest average ranking. At the same time, the evaluation also goes to the
PH value, total amount of sugar and alcohol content; where the PH value is measured by PH
meter; the total sugar is measured by fehling reagent; and the alcohol degree is measured by the
alcohol meter. Specific types of yeast and grouping are shown in Table 7.
Table 7 Initial Screening of Different Types of Yeasts
Yeast Cross-Evolutio
n
BM4X4 D47 QA23 Angel
Temperature
(°C)
20 20 20 20 20
Initial Sugar
Degree (°C)
24.5 24.5 24.5 24.5 24.5
(2) Three types of yeast with optimum performance, which are initially selected in the last
experiment, are adopted here, provided that these yeasts are respectively Yeast X, Y and Z;
then fermentation temperatures are chosen based on their optimum temperature range for
production of wine, i.e. the optimum fermentation temperature for X is a, for Y is b and for Z is
c. In addition to the fermentation temperature, the rest of the fermentation conditions and the
adding medication stay the same as the experiment above. The sensory evaluation and the
physicochemical index measurement are carried out in accordance with the methods of the

14. 14
experiment above. Specific types of yeast and grouping are shown in Table 8.
Table 8 Screening of Different Types of Yeast
Yeast X Y Y
Temperature
(°C)
a b c
Initial Sugar
Degree (°C)
24.5 24.5 24.5
2.4.4.2 Technology Optimization of Rose Flavour Mead Brewing
In order to optimize the brewing technology of rose flavour mead, the orthogonal
experiment method is adopted to explore the effects of 3 factors on the adding amount of PVPP,
VC and the initial sugar degree. The level of each factor is established based on the result of
the single-factor experiment; then a sensory evaluation team composed of 10 people with
professional wine-tasters of Level I and Level II shall be put together for an overall rating of
each group. The assessment standards go to the color, flavour and taste. Finally, the reference
index will be the average score of the sample from every group. L4 (33
) will be chosen in the
experiment in accordance with the operation steps based on the process above. Specific level of
factor is shown in Table 9.
Table 9 Level of Factors in the Rose Flavour Mead Brewing
Level Factors
Initial Sugar
degree /°(A)
Vc/ g/L (B) PVPP/ g/L (C)
1 22（A1） 0.03（B1） 0.25（C1）
2 24.5（A2） 0.06（B2） 0.3（C2）
3 27（A3） 0.09（B3） 0.35（C3）
3. Results and Analysis

15. 15
3.1 Single-factor Experiment Results of Dried Rose Water Leaching
3.1.1 Leaching Ratio between the Dried Roses and Water
Conduct leaching experiments by adopting different leaching ratios of dried roses and
water, and get score results in light of sensory evaluation based on different evaluation
standards. For details, see Table 10.
Table 10 Effects of Different Leaching (Dried Rose Water Leaching) Ratios on Sense
No. CK 1 2 3 4
Leaching Ratio
of Dried Rose
(%)
0 0.3 0.5 0.7 1
Comprehensive
Average Score of
Sense
1 2.1 2.7 2.4 1.5
According to Table 10, the sensory evaluation data in the Table presents a peak value.
After comprehensive evaluation,Group 2 which is added with 0.3% of dried rose samples has
the optimal performance in flavour and taste. According to the data variation tendency as
shown in the Table, we can predict that the optimal leaching ratio lies between 0.5% and 0.7%.
By analysis, we choose two points of 0.5% and 0.65% as leaching factor levels for further
orthogonal experiments.
3.1.2 Leaching Temperature of Dried Roses
Conduct leaching experiments at different temperatures, and get score results in light of
sensory evaluation based on different evaluation standards. For details, see Table 11.
Table 11 Effects of Different Leaching (Dried Rose Water Leaching) Temperatures on Sense
No. CK 1 2 3 4
Water Bath Room 55 70 85 97

16. 16
Temperature (°C) Temperatur
e (23°C)
Comprehensive
Average Score of
Sense
2.1 2.1 2.5 2.4 2.3
According to Table 11, the sensory evaluation data in the Table presents a peak value.
After comprehensive evaluation, group 2 which presents water bath samples at 70℃ has the
optimal performance in flavour and taste. According to the data variation tendency as shown in
the Table, we can predict that the optimal bath temperature lies between 70℃ and 85℃. By
analysis, we choose two points of 70℃ and 80℃ as temperature factor levels for further
orthogonal experiments.
3.1.3 Leaching Time of Dried Roses
Conduct leaching experiments at different leaching times, and get score results in light of
sensory evaluation based on different evaluation standards. For details, see Table 12.
Table 12 Effects of Different Leaching (Dried Rose Water Leaching) Time on Sense
No. CK 1 2 3 4
Leaching Time
(min)
Put in and
Pick up
Immediatel
y
15 35 55 65
Comprehensiv
e Average
Score of Sense
1.1 3.1 2.8 2.4 2.2
According to Table 12, the sensory evaluation data in the Table presents a peak value.
After comprehensive evaluation, Group 1 which takes 10min in water bath leaching has the

17. 17
optimal performance in flavour and taste. According to the data variation tendency as shown in
the Table, we can predict that the optimal water bath time lies between 15min and 35min. By
analysis, we choose two points of 15min and 30min as time factor levels for further orthogonal
experiments.
3.2 Technology Optimization of Dried Rose Water Leaching
Table 13 Orthogonal Experiment Results and Range Analysis on Dried Rose Water Leaching
Disposal
Factors
Leaching
Temperature
Leaching
Ratio
Leaching
Time
Sensory Score
1 1（70℃） 1（0.5%） 1（15min） 4.6
2 1 2（0.65%） 2（30min） 4.9
3 2（80℃） 1 2 4.7
4 2 2 1 5.2
T1 9.5 9.3 9.8
T2 9.9 10.1 9.6
Average x1 4.75 4.65 4.9
Average x2 4.95 5.05 4.8
R 0.2 0.4 0.1
According to Table 13, when conducting the water bath leaching of dried roses, we
take comprehensive scores of sensory evaluation as judgment standards, and conclude that the
effect of various factors on leaching result is B>A>C, that is, the leaching ratio has the largest
effect, followed by temperature influence, and the time has the least effect. Within the
experiment range, the optimal combination in theory is A2B2C1; the optimal combination in
reality is A2B2C1; and the optimal combination in theory under the experimental scheme is
also the optimal combination in reality, therefore the optimal combination is A2B2C1. That is
to say, the most suitable combination of leaching factors is leaching temperature at 80°C,

18. 18
ODValueUnderA420
addition of 0.65% dried roses, and leaching time of 15min.
3.3 Browning Inhibition Effects of PVPP and Vc on the Dried Rose Leaching Liquor
Dispose of the leaching liquor by adopting different actuating quantities of PVPP and Vc,
measure A420 OD values of each group of samples at regular intervals on a daily basis, and
draw variation curve chart. For details, see Chart 1.
Chart 1 Effects of Different Usage Amount of PVPP or Vc on Browning Degrees of
Leaching liquor

19. 19
According to Chart 1, the A420 OD value of leaching liquor shows that the browning
degrees constantly rise with the increase of time. On the first day, the OD values of samples
which have gone through PVPP or Vc disposal are less than those of CK group and
refrigeration group; the reason may be that, on the first day, the easy-browning substances
generated from heating by disposing group are absorbed by PVPP or reduced by Vc, while CK
group has not made any relevant browning inhibition disposal, therefore the browning degree
is higher than that of disposing group. On the first to fourth days, the browning degree
variation becomes relatively violent; the browning variation speed sequence is CK group > Vc
group > PVPP group, and the reason may be that Vc group itself is oxidized with color
generation although the added Vc inhibits the browning of easy-browning substances in the
leaching liquor, while PVPP group has gone through polyphenols adsorption, which makes
polyphenols concentration relatively low and browning speed relatively slow in this period. On
the following fifth to eighth days, the browning degree variation is relatively gentle, but the
browning variation speed sequence is CK group > PVPP group > Vc group, and the reason may
be that Vc has relatively completed color generation reaction, achieves balance with the
browning reaction, while PVPP group's polyphenols constantly increases with the change of
time and its browning reaction speeds up. For the result concerns, PVPP and Vc can be used
together. It can be predicted from variation trend and variation end point of curve line that the
optimal range of PVPP usage amount is 0.2g/L~0.4g/L. By analysis, we choose three points of
0.25g/L, 0.3g/L and 0.35g/L as PVPP addition factor levels for further orthogonal experiments;
on the other hand, it can be also predicted that the optimal range of Vc usage amount is
0~0.1g/L. By analysis, we choose three points of 0.03g/L, 0.06g/L and 0.09g/L as Vc addition
factor levels for further orthogonal experiments.
3.4 Screening of Optimal Yeast Species
(1) Adopt 5 species of yeast to ferment at the same temperature of 20°C, rank them in
light of sensory evaluation, and choose the superior three species of yeast by measuring such
three physicochemical indexes as alcohol content, residual sugar content and pH value. For

20. 20
details, see Table 14.
Table 14 Effects of Different Yeast Species on All Indexes of Products after Fermentation
Yeast Species Cross-Evoluti
on
BM4x4 D47 QA23 Angel
Final pH
Value
3.21 3.01 3.04 3.27 3.20
Alcohol
Content (°)
5.4 9.9 6.1 12.9 12.6
Residual
Sugar
Content (g/L)
130 45 115 11 22
Remarks Rose, bright
color, strong
flavour,
typical
fragrance,
harmoniously
mellow and
sweet taste,
fresh body
Dark rose,
bright color,
comfortable
flavour,
piquant taste,
obvious
acidity,
astringent
feints
Dark rose,
bright color,
light flavour,
harmoniously
acid and
sweet taste,
fresh and
clear feints
Orange red,
bright color,
obvious
ferment
flavour, acid
taste, slight
bitter body
Rose, bright
color,
common
flavour,
typical
fragrance,
obvious
acidity, slight
lack of
harmonious
body
Rank 1 4 2 5 3
According to Table 14, for the sensory evaluation rank, the top three yeast samples are
Cross-Evolution, D47 and Angel respectively, having rose, bright color, strong fragrance,
harmonious body and clear feints. While the Cross-Evolution and D47 may have low alcohol

21. 21
content and high sugar content under improper temperature. The temperature may be adjusted
as the most proper one to ferment during the following yeast screening experiment.
Additionally, the initial pH values of the five samples are 3.1, while the final pH values of
those are 3.0-3.3. It is concluded that the pH values have little change during fermentation and
ageing. After analyzing, Cross-Evolution, D47 and Angel are finally selected for further
screening.
(2) The three preferred yeasts selected from the last experiment will be fermented under
its most proper fermentation temperature and ranked according to the sensory evaluation. The
best yeast species will be selected by measurement on three physicochemical indexes regarding
the alcohol content, residual sugar content and pH value. For details, see Table 15.
Table 15 Effects of Different Yeast Species on All Indexes of Products after Fermentation
Yeast Species Cross-Evolution D47 Angel
The Most Proper
Fermentation
Temperature (°C)
14 18 23
pH Value 3.28 3.13 3.22
Alcohol Degree (°) 9.9 11.8 12.5
Residual Sugar (g/L) 48.60 22.92 10.60
Remarks Orange red, slight
dark color, obvious
honey flavour with
light fragrance, sweet
taste, harmoniously
acid and sweet, soft
and smooth,
astringent aftertaste
Rose, muddy color,
harmonious honey
smell and fragrance,
slightly bitter,
astringent and acid
taste, tasteless body
Orange red, slight
dark color, strong
rose flavour, bitter,
astringent and acid
taste, mellow body,
clear feints, short
aftertaste
Rank 1 2 2

22. 22
According to the Table 15, for the sensory evaluation rank, the best is Cross-Evolution
yeast, having harmony on fragrance and honey flavour, everlasting acid and sweet and soft
body. Although the alcohol degree is low and the residual sugar content is high, it forms good
smell and flavour. Additionally, a slightly high pH value also forms good flavour with harmony
of acid and sweet. As a result, Cross-Evolution is finally selected as the best fermentation yeast
in the five yeast species. From observation during the experiment, 14°C is the most proper
fermentation temperature for Cross-Evolution yeast in theory, while the fermentation with a too
slow speed and longer time will cause incomplete fermentation and easy contamination. Thus,
18°C is finally selected as the fermentation temperature for the orthogonal experiment
according to results from analyzing and the last two fermentation experiment.
3.5. Technology Optimization of Rose Flavour Mead Brewing
Table 16 Technology Optimization of Rose Flavour Mead Brewing
Disposal Factors
Fermentation
Temperature
PVPP Vc E Sensory
Score (Lower
Score, Better
Sense)
1 1 (22°) 1
(0.03g/L)
1
(0.25g/L)
2 31
2 1 2
(0.06g/L)
2 (0.3g/L) 1 28
3 1 3 (0.09
g/L)
3
(0.35g/L)
3 32
4 2 (24.5°) 1 2 1 18
5 2 2 3 3 21
6 2 3 1 2 34

23. 23
7 3 (27°) 1 3 3 5
8 3 2 1 2 23
9 3 3 2 1 13
T1 91 54 88 59
T2 73 72 59 88
T3 41 79 58 58
Average x1 30.33 18 29.33 19.67
Average x2 24.33 24 19.67 29.33
Average x3 13.67 26.33 19.33 19.33
Table 17 Variance Analysis for the Orthogonal Experiment of Rose Flavour Mead Brewing
Factors Sum of
Squares of
Deviation
Degree of
Freedom
F Ratio F Critical
Value
Significance
A 427.556 2 36.999 19.000 *
B 110.889 2 9.596 19.000
C 193.556 2 16.749 19.000
e 11.556 2 1.000 19.000
Deviation 11.56 2
According to Table 16 & 17, during the rose flavour mead brewing, all factors effects on
the leaching results are A>C>B based on the score from the sensory evaluation. It means that
the initial sugar is the greasiest effect factor, Vc addition second and PVPP addition third.
Within the experiment range, the best combination in theory is A3B1C3 and in practice
A3B1C3. The best combination in theory is similar to that in practice in the experiment scheme.
The best combination for leaching factors is 27° sugar, 0.03g/L Vc, and 0.09g/L PVPP.
Table 18 Physicochemical Indexes and Sensory Evaluation for Rose Flavour Mead

24. 24
No. 1 2 3 4 5 6 7 8 9
Final
pH
Value
3.09 3.38 3.27 3.11 3.16 3.20 3.18 3.26 3.12
Alcoho
l
Degree
(°)
12.20 11.50 12.5 13.30 13.50 13.10 14.10 13.30 12.90
Re
sidual
Sugar
Conten
t (g/L)
19.22 22.50 29.72 42.72 34.20 34.44 49.70 53.10 38.90
Remar
ks
Dark
rose,
bright
color,
comfort
able
fragranc
e, crisp
and
slight
bitter
taste,
harmoni
ous
flavour
Orange
red,
bright
color,
fragranc
e, crisp
and
well-bal
anced
taste,
bitter
feints,
obvious
ferment
flavour
Orange
red,
bright
color,
well-bal
anced
honey
and
fragranc
e,
comfort
able
taste
with
acid and
Dark
rose,
bright
color,
harmoni
ous
honey
and
fragranc
e, crisp
and
mild
taste,
acid
feints,
Rose,
dark
color,
little
fragranc
e, good
taste,
strong
wine
taste,
harmoni
ously
acid and
sweet
Orange
red,
slight
muddy
color,
strong
honey,
moderat
e acid
and
sweet,
strong
bitter
Rose,
bright
color,
comfort
able
fragranc
e,
ferment
smell,
soft
taste,
harmoni
ously
acid and
sweet,
Orange
red,
slight
muddy
color,
good
fragranc
e and
honey,
soft
taste,
harmoni
ously
acid and
sweet,
Dark
rose,
bright
color,
strong
ferment
flavour,
good
taste,
strong
wine
taste,
moderat
e acid
and

25. 25
ferment
flavour,
slight
bitter
bitter
and
harmoni
ous
flavour
slight
bitter
feints
bitter
feints
sweet,
harmoni
ous
flavour
Rank 7 6 8 3 4 9 1 5 2
According to Table 18, when the fermentation temperature is adjusted to 18°C, the
residual sugar content will decrease; alcohol degree generally increases to more than 11°, and
fermentation completeness and taste enhance with harmoniously acid and sweet, soft taste,
mellow body, and flavour similar to ice white spirits or noble wine. With combined use of
PVPP and Vc, not much change in color and flavour of the mead within a longer fermentation
and ageing time occurs, in which the color remains red and transparency of rose leaching liquor
with attractive vision and it varies with the pH value in favor of subsequent color modulation
of products; and harmonious fragrance, honey and bouquet forms unique flavour.
3.6 Quality Indexes of Finished Mead
3.6.1 Sensory Indexes
Table 19
Items Indexes
Appearance Bright, glossy
Color Rose Red

26. 26
Taste Harmoniously acid and sweet, soft without
foreign smell
Flavour Harmonious honey and rose fragrance
Impurities No deposits, impurities or obvious suspended
solids
3.6.3 Physicochemical Indexes
Table 20
Items Indexes
Alcohol Degree (°) 14.10
Residual Sugar Content (g/L) 49.70
pH Value 3.18
4 Discussion
4.1 Effect Factors of Dried Rose Leaching
The Research shows that during dried rose leaching, leaching ratio plays a primary role in
the leaching effect, while the leaching temperature and leaching time play a secondary role.
The leaching ratio directly affects the amount of flavour substances released from dried rose
leaching, which means it will affect the rose flavour in products during subsequent
fermentation. While the leaching temperature and time affect the efficiency of flavour
substances released from dried rose leaching and release of some substances with off-flavour,
greatly affecting the product quality at last. However, some minor factors affecting leaching
also are neglected, such as quality and pH value of dried rose; meanwhile, the experiment only
evaluates the sense without quantization determination of substances affecting flavour released
from leaching (such as polysaccharide, flavone, anthocyanin, tannin, etc.). According to
previous researches, the dried rose leaching is not limited for a single water leaching; the
multiple times of leaching, ethanol leaching, enzymolytic leaching and other methods are often

27. 27
adopted to improve the leaching efficiency. Through a research on adoption of multiple times
of leaching for rose beverage with Xu Huaide and other researchers (2003), and by comparison
with respective research on flavone, polysaccharide and anthocyanin leaching from rose by
adoption of the ethanol leaching by Zhou Xiaoqi (2010), Ma Meifan (2009), Li Zijiang (2009),
et al., the leaching ratio and temperature adopted for the research is low and the time is short.
In addition, a single leaching is adopted with simple leaching process. By comparison with the
research on jasmine tea by adoption of the enzymolytic leaching by Zheng Ping, a physical
leaching method is adopted for the experiment without adoption of a biochemical method. As a
result, the leaching efficiency of the experiment probably is lower than the previous researches.
While the single leaching adopted for the leaching ratio, leaching temperature and leaching
time for the experiment have a simple process, low consumption of materials without addition
of substances affecting subsequent fermentation (such as ethanol), playing a practical role in
subsequent industrial application. In addition, methods adopted for the previous researches
may badly affect the overall flavour of leaching liquor from dried rose, which may improve
release efficiency of flavour substances and promote release of off-flavour or affect subsequent
fermentation. To sum up, the research aims to find out a better leaching parameter by
improving leaching efficiency to a great extent, without affecting the overall flavour and
subsequent fermentation.
4.2 Combined Utilization of Browning Inhibitor
It is found in the research that combined utilization of PVPP and Vc has better browning
inhibition effect, in which Vc is better than PVPP. Vc has reducibility and can replace most
easy browning flavour substances to be oxidized. Due to Vc long-term existence in
fermentation liquor, it will have an effect in browning inhibition to the greatest extent. While
PVPP absorbs easy browning polyphenols after leaching and the fermentation liquor has been
extracted before leaching, thus, the effect is minor. Vc has been featured by changes in color
and flavour after oxidization, so single utilization of it will brown the fermentation liquor
fermented previously to a great extent; while PVPP may effectively control browning at
previous fermentation via absorbing browning polyphenols. Polyphenols and the browning

28. 28
extent increase at latter fermentation. As a result, PVPP and Vc finally supplement each other
through combination. Yi Guobin and other researchers (2001) also make a conclusion that the
better browning inhibition effect is obtained via combined utilization of PVPP and Vc. Effects
of PVPP crosslinking degree and operative temperature are explored in researches made by Yi
Guobin and other researchers, while on one hand, the research is lack of such experiment and
further exploration into PVPP features. On the other hand, neither relevant factor experiment
for Vc playing an vital role in anti-browning action nor orthogonal experiment on PVPP and
Vc are conducted. While Zhao Guangyuan and other researchers[9]
deeply explore into various
browning inhibitor, including Vc application and consider that a better browning inhibition
effect can be obtained via combined utilization of different browning inhibitor, in which PVPP
is not included.
4.3 Screening of Best Yeast
It is found in the Research that Cross-Evolution yeast is suitable for brewing rose flavour
mead. The research selects 5 kinds of common fruit wine yeasts, finding that the
wine-producing capacity of Cross-Evolution yeast and its fermentation efficiency are relatively
low, but it has a good adaptability. The product is soft and harmonious without losing original
rose flavour. While yeasts, such as white spirits, rice wine and other wine, are not adopted for
the research, and the research scope is slightly narrow. The results are also different from some
previous researches. A. Roldán (2010) and other researchers consider that a brewing yeast
separated from Portuguese honey is more suitable for honey brewing. The yeast has a higher
tolerance level for alcohol, SO2 and hypertonic environment. In the research, no experiment on
capacities of Cross-Evolution regarding alcohol tolerance, SO2 and hypertonic environment is
conducted, so understanding of performance of the yeast is inadequate and comparison with
such brewing yeast separated from honey may not be conducted. However, the advantage of
Cross-Evolution is in perfectly maintaining the rose flavour in the leaching liquor, producing
harmoniously acid and sweet taste and more complying with the research requirements on
mead products.
5 Conclusion

29. 29
5.1. Research Results
The research explores ideal process parameters for leaching, browning inhibition
disposal and mead brewing of dried rose prior to fermentation. The experiment results show
that dried rose may have better fragrance and flavour for 15min leaching and with the leaching
ratio of 0.65% and leaching temperature of 80°C; browning inhibition an be effectively
controlled with addition of 0.09g/LPVPP and 0.03g/LVc; and products with harmonious
fragrance, harmoniously acid and sweet, and soft taste may be obtained by adjusting the initial
sugar degree to 27°, inoculating Cross-Evolution yeast and setting the fermentation
temperature at 18°C.
5.2 Innovative Points in the Research
A new process of mead brewing with fermentation of a natural perfume (rose) which is
concluded from the research is a new try and breakthrough in the alcoholic fermentation
process using both natural perfume and honey.
5.3 Subjects Necessary for Further Research
(1) Mead fermentation needs a lower fermentation temperature with a longer time and
often has incomplete fermentation. Researches show that addition of natural perfume may
speed up mead fermentation, while there is no detailed, accurate and systematic exploration.
Thus, we can conduct further researches on this aspect.
(2) Each composition and its content in mead need to be further researched by gas
chromatography.
(3) Mead types with addition of different natural perfume, such as jasmine, osmanthus
fragrans, chrysanthemum, etc. still need to be further researched and explored.
(4) Rose leaching and mead fermentation need to be combined in a better way. In
addition, researches on whether rose is added for fermentation and different factors' influence
on honey fermentation shall be conducted.

30. 30
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32. 32