1. Postharvest losses

2. Postharvest Biology
• A practical science.
• Primarily deals with Perishable Commodities.
• Postharvest = After Harvest
• Concerned with the harvest of the crop
(when & how to harvest; maturity standards).
• Also in pre-harvest factors (seed source, rootstock, etc.)
because they strongly influence postharvest quality.
The fruit quality is set during growth.
• Ultimately, the maximal
product quality is determined
at harvest.

3. The Postharvest Goals
• Harvest the product at its optimum maturity.
• Maintain the product’s internal and external quality
throughout packing, storage and distribution.
It is Alive during this process!
• Deliver the fruit to consumers at the time and in a form
(e.g. ripe, cut up, etc.) that they will purchase it.

4. Historical background
Early postharvest practices:
• Dried fruits, vegetables, meats, pickles, etc.
• Fermentation of juices.
• Salting or smoking.
All these methods KILL the product!
It is easier to transport and store the products.

5. Historical Background
Early Storage Practices:
• Basket making developed by 7,000 B.C.
• Underground pits and silos by 9,000 B.C.
Silos were the major means of long term storage by Roman
times.
• Roman era – modified atmosphere storage of grains.
• 1803- Ice refrigeration developed.
• 1855- mechanical refrigeration was invented.

6. • 1872 - ice refrigerated rail cars were common.
• 1889 - ammonia refrigeration was widely used to make ice.
• 1928 - mechanical refrigerated displays used in retail stores.
• 1927 - Controlled atmosphere studies begun.
• 1929 - Commercial CA storage built in England.
Historical Background

7. Postharvest issues became important when cities developed:
• The Industrial Revolution (18th century).
• The Problem:
How to deliver fresh fruits and vegetables from areas of
production to areas of consumption and keeping their quality?
Historical Background
All fresh produce is alive
↓
The Challenge is to Keep Healthy Until Consumed!

8. World-Wide Perspective
• World population has reached almost 7 billion.
• Technological advances have helped to feed much of the
world (e.g. China, India & Brazil).
• Many parts of the world still in need.
Western style, capitol intensive methods often not suitable
for an area.

9. Food distribution is a major worldwide problem:
• Urbanization expected to continue at a greater rate in
developing countries.
• Produce grown in these areas are the least
studied.
Worldwide production (2001):
• Cereals (durable food goods) = ~2.1 billion MT.
• Fruits, Vegetables, Roots & Tubers =~1.8 billion MT.
World-Wide Perspective

10. Overlap of world hunger and world poverty
% of population
earn less than
1.25 $ per day
% of population
undernourished

11. World overall production of
vegetables and fruits (1000 tones)
0
500,000
1,000,000
1,500,000
1994-
1996
1999-
2001
2005 2006 2007
vegetables fruits
FAO Statistical Yearbook 2009

12. The importance of postharvest
The increase of vegetables
and fruit production:
• Population growth.
• Higher standard of
living.
• Awareness for
nutritional value of food.
0
200
400
600
800
1000
1200
1400
1600
1970 1980 1990 1994
Africa Asia
South/Central America USA/Canada
Europe Oceania
Million tons fruits and vegetables
Fruit and vegetable
production increased
by 44%
between 1970 to 1994
India: No 3 of the world fruit and
vegetables producer. About 50% of
the products deteriorates until
reaching the consumer.
Therefore, consumption is low and
prices are high.

13. 0
200
400
600
800
1000
1970 1980 1990 1994
Africa Asia
South/Central America USA/Canada
Europe Oceania
Million tons fruits and vegetables
without root crops
Fruit and vegetable
production
increased by 75%
between 1970 to 1994
(not including roots
and tubers)
China and India produce
30% of the world fruits
and vegetables.
The importance of postharvest

14. Characteristics of Perishable
Commodities
Compared to grains:
• More subject to deterioration after harvest
(shelf life days to months vs. > 1yr).
• Relatively larger in size (up to 5 kg vs. < 1g).
• Soft textured.
• Higher water content (70 to 90% vs. 10 to 20%).
• Higher respiration and heat production.

15. Estimated Postharvest Losses
very rough estimates are available:
• 5 to 25% in developed countries.
• 20 to 50% in developing countries.
• In the US, a large portion of loss occurs at the consumer.
Loss of product
is much more than
just the cost of the commodity

16. The other losses
• Energy & labor loss (e.g. during packinghouse operations).
• Loss of materials (e.g. packaging).
• Cost of waste disposal.
• Loss of food value (e.g. nutrients).
• Loss of organoleptic quality:
Color changes
Water loss
Carbohydrate changes.
Volatile changes
Breakdown of proteins, cell wall components, softening, etc.

17. Causes of Postharvest Loss
Internal Factors:
• Respiration.
• Compositional changes.
• Morphological changes.
• Physiological disorders.
• General senescence.

18. Environmental Factors:
• Temperature
• Physical damage
• Pathogens
• Relative humidity
• Atmospheric composition
• Light
• Gravity
• Rodents and other animals
• Contamination
Causes of Postharvest Loss

19. Perishable Commodities are still alive!
They consume oxygen and produce carbon dioxide
Sugar+ O2
↓
Energy + CO2 + Water + Heat

20. Respiration and Shelf Life
Respiration rate and shelf life are inversely related.
Higher respiration
↓
Shorter Shelf Life

21. Temperature & Respiration
• Temperature is the most important factor influencing the
postharvest life of the given commodity.
• Temperature dictates the speed of chemical reactions
including respiration.
• Typically, for every increase of 10oC, the respiration
increases between 2 and 4 fold.
R1=Respiration at Temperature 1 (T1)
R2=Respiration at Temperature 2 (T2)
Q10= R2
R1
10
T2-T1

22. The affect of temperature
The affect of temperature on broccoli after 48 hr of storage
at either room temperature or in cold storage
24oC 4oC

23. Postharvest compositional changes
• Water loss
• Nutrients
• Vitamins
• Antioxidants
• Starch to Sugar to Starch

24. Water Loss
Water Loss resulting a direct loss of salable weight as well
as quality loss:
• Appearance quality - wilting, shriveling, and accelerated
development of injuries.
• Textural quality – loss of crispness, juiciness, etc.
• Nutritional quality – e.g. vitamins A & C.
Rate of water loss influenced by:
• Environmental factors – e.g. relative humidity.
• Anatomical factors – stomates, hairs, etc.

25. Postharvest Morphological Changes
• Horticultural commodities are living products and
sometimes are still growing. Therefore, they often continue
development in ways that sometimes reduce quality.
Changes include:
• Sprouting (onions, tubers, root crops)
• Rooting (onions, root crops)
• Elongation & Curvature (asparagus, gladiolus)
• Seed Germination (lemon, tomato, pepper)

26. Postharvest Physiological Disorders
A tissue damage or breakdown which not related to
pathogens, insects or mechanical damage.
Temperatures
• chilling injury, freezing injury or High temperature injury.
Altered atmospheric gas concentrations.
• Low O2 or Elevated CO2.
Nutrition
• As calcium deficiency or boron toxicity.

27. Chilling Injury
• Physiological injury to some commodities held at
temperatures above freezing.
• Susceptible crops include:
Sapote
Cucumber
Eggplant Okra
Pepper
Sweet Potato
Tomato
Mango
Olive
Papaya
Passion fruit
Pineapple
Plantain
Pomegranate
Avocado
Banana
Cherimoya
Citrus
Feijoa
Guava
Jujube

28. Chilling Injury
• Occurs mainly in commodities from subtropical & tropical
origins.
• Injury caused by exposing fruit to low temperatures above
freezing, between about (5 to 15 oC).
• Injury becomes more noticeable after transferring to non-
chilling temperatures (shelf life).

29. Chilling Injury
Symptoms:
• Surface pitting
• Discoloration (external/internal)
• Water-soaked areas
• Necrotic areas
• uneven ripening or failure to ripen
• Greater susceptibility to decay
• More…

30. Causes of Postharvest Loss
Environmental Factors
Light
Temperature
Gravity
Physical damage
Rodents and
other animals
Pathogens
Contamination
Relative humidity
Atmospheric
Composition

31. Temperature
• Mentioned above with respiration
and physiological disorders.
• Temperature greatly effects water
loss.
• Lower temperature also slows
pathogen development.

32. Physical Damage
• Causes the greatest amount of loss to fresh horticultural
products.
Physical Damage Affects:
• Respiration, ethylene production, ripening, and other
metabolic processes.
• Pathogen growth and ability to invade tissue.
• Tissue discoloration.

33. Pathology (decay)
• Fungi (major), bacteria and viruses.
• Preharvest (latent) and postharvest infections.
• Most postharvest infections are a result of
rupturing the epidermis of the commodity.

34. Relative Humidity
• Higher relative humidity slows water loss from the commodity.
• High relative humidities (95 to 100%) might weaken the
cartons.
• Free moisture stimulates pathogen development.
5%
10%
15%

35. Atmospheric Composition
Modified or Controlled Atmospheres:
Modified Atmospheres (MA):
• Altering the normal gas composition surrounding a commodity
(e.g. raising or lowering O2 or CO2 concentrations).
• Passive. The commodity is placed in a gas impermeable
container and the crop’s respiration consumes (lowers) O2 and
gives off (increases) CO2.
Controlled Atmospheres (CA):
• Same as MA, except gas concentrations are actively
regulated using special equipment.

36. Modified Atmospheres - Advantages
• Slows down respiration and other
metabolic processes
(ripening & senescence).
• Reduces sensitivity to ethylene
(at < 8% O2 or >1% CO2.
• Reduces development of some
physiological disorders
(chilling injury).
• May inhibit pathogen development.
• Can be used to kill insects.

37. Modified Atmospheres - Disadvantages
• Can cause or exacerbate some physiological disorders
(black heart in potatoes).
• Can cause irregular ripening.
• Can result in off-flavors or odors if anaerobic respiration
occurs.
• Any MA or CA related injuries stimulate pathogen
development.
• May delay periderm development and stimulate sprouting
in root or tuber crops.

38. Causes of Postharvest Loss
Environmental Factors:
• Light- Color and morphological changes (potato greening).
• Gravity- Morphological changes (bending).
• Rodents and other animals.
• Contamination (food safety).

39. Postharvest
Commercial Considerations
Preharvest factors:
• Cultivars.
• Nutrition and Water effects.
• Weather conditions (e.g. temperature, humidity)
• Field sanitation (both for decay & human pathogens).
Harvesting:
• Best time to harvest for fresh, processing, storage?
Preliminary grading in the field:
• Remove unmarketable produce ASAP.

40. Postharvest
Commercial Considerations
Packing operations:
• Washing, sorting, sizing, grading, waxing, and more.
• Each step costs, therefore use only if increases value of the
crop.
Packaging:
• Protects the product, reduces water loss, organize the product,
excludes light & communicates information.
• Must be economic, able to support stacking, allow ventilation
(cooling), facilitate recycling or disposal at destination markets.

41. Postharvest Maturation:
• Ethylene degreening or ripening.
• Curing.
Rapid cooling:
• Air cooling
• Room
• Forced-air
• Hydrocooling
• Ice Cooling
(Top icing, Liquid ice injection)
• Vacuum Cooling
Postharvest
Commercial Considerations

42. Storage:
• increases the cost of the product.
• Critical accuracy of temperature and RH%.
• CA or MA storage.
Transportation:
• By water – inexpensive but slow.
• Trains – more expensive but faster.
• Truck – predominant method. Fast & reliable.
• Air – Fastest, expensive, & inconsistent scheduling and
temperature control.
Postharvest
Commercial Considerations

43. Marketing:
• Identify markets and qualities desired.
• Entire process to deliver what the consumer will buy.
Retailing:
• Educate the retailer how to handle your commodity.
• Continuation of temperature, RH and sanitation chain.
Postharvest
Commercial Considerations