A lecture on Loss Assessment and Quality Evaluation

1. Lecture 7
LOSS ASSESSMENT AND
QUALITY EVALUATION OF
FRUITS AND VEGETABLES

2. 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.

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

4. History of Postharvest Practices
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.

5. • 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

6. 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.

7. 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

8. The other losses
• Energy and 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.

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

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

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

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

13. 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.

14. The affect of temperature
The effect of temperature on broccoli after 48 hr
of storage at either room temperature or in
cold storage
24o
C 4o
C

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

16. 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.

17. Water Loss
Rate of water loss influenced by:
• Environmental factors – e.g.
relative humidity.
• Anatomical factors – stomates,
hairs, etc.

18. Postharvest Morphological Changes
• Sprouting (onions, tubers, root crops)
• Rooting (onions, root crops)
• Elongation & Curvature (asparagus,
gladiolus)
• Seed Germination (lemon, tomato,
pepper)

19. 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.

20. 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
o
C).
• Injury becomes more noticeable
after transferring to non-chilling
temperatures (shelf life).

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

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

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

24. Thank You!