Postharvest losses

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 determinedat harvest.

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.

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.

Historical BackgroundEarly 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.

• 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

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!

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.

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 leaststudied.Worldwide production (2001):• Cereals (durable food goods) = ~2.1 billion MT.• Fruits, Vegetables, Roots & Tubers =~1.8 billion MT.

World-Wide Perspective

Overlap of world hunger and world poverty

%of population earn less than 1.25 $ per day

%of population undernourished

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

The importance of postharvest

The increase of vegetables and fruit production:

• Population growth.• Higher standard of living.• Awareness for nutritional

value of food. 0

200400600800

1000120014001600

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.

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

Characteristics of PerishableCommodities

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.

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

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 lossCarbohydrate changes.Volatile changesBreakdown of proteins, cell wall components, softening, etc.

Causes of Postharvest Loss

Internal Factors:

• Respiration.

• Compositional changes.

• Morphological changes.

• Physiological disorders.

• General senescence.

Environmental Factors:• Temperature• Physical damage• Pathogens• Relative humidity• Atmospheric composition• Light• Gravity• Rodents and other animals• Contamination

Causes of Postharvest Loss

Perishable Commodities are still alive!

They consume oxygen and produce carbon dioxide

Sugar+ O2

↓

Energy + CO2 + Water + Heat

Respiration and Shelf Life

Respiration rate and shelf life are inversely related.

Higher respiration

↓

Shorter Shelf Life

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

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

Postharvest compositional changes• Water loss

• Nutrients

• Vitamins

• Antioxidants

• Starch to Sugar to Starch

Water LossWater Loss resulting a direct loss of salable weight as well as quality loss:• Appearance quality - wilting, shriveling, and accelerateddevelopment 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.

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)

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.

Chilling Injury

• Physiological injury to some commodities held attemperatures above freezing.• Susceptible crops include:

Avocado

Banana

Cherimoya

Citrus

Feijoa

Guava

Jujube

Mango

Olive

Papaya

Passion fruit

Pineapple

Plantain

Pomegranate

Sapote Cucumber

Eggplant Okra

Pepper

Sweet Potato

Tomato

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).

Chilling Injury

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

Causes of Postharvest Loss

Environmental Factors

TemperatureLight

Physical damageGravity

PathogensRodents and other animals

Relative humidityContamination

Atmospheric

Composition

Temperature

• Mentioned above with respiration and physiological disorders.

• Temperature greatly effects water loss.

• Lower temperature also slows pathogen development.

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.

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.

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%

Atmospheric CompositionModified 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 activelyregulated using special equipment.

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.

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.

Causes of Postharvest Loss

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

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.

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.

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

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

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