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 determined at 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 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.

Historical Background • 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? 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.

World-Wide Perspective 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.

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) FAO Statistical Yearbook 2009

The importance of postharvest Million tons fruits and vegetables The increase of vegetables and fruit production: Population growth. Higher standard of living. Awareness for nutritional value of food. 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. Fruit and vegetable production increased by 44% between 1970 to 1994

The importance of postharvest 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.

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.

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 loss Carbohydrate changes. Volatile changes Breakdown of proteins, cell wall components, softening, etc.

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

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

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) 10 T2-T1 Q10= R2 R1

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 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.

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 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

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 Light Temperature Gravity Physical damage Rodents and other animals Pathogens Contamination Relative humidity 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. 15% 10% 5%

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.

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 Commercial Considerations 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.