Section III Fresh Fruit and Vegetables Quality and Safety Maintenance and Enhancement during the Post-harvest Chain
quality products are produced in the fields! but, the quality of a product is maintained and enhanced during its harvest and post-harvest management.
Now it is waste...how many opportunities have been lost!
Principles of postharvest management of FFV • Product quality maintenance (reduce loses) • Generate product added value • Generate market opportunities
Inappropriate post-harvest handling • Product loses. (Quality decay/physical loses). • High costs and low profits. • Loss of market opportunities. • Low competitiveness.
Fruits and vegetables as PERISHABLE products Key processes during the post-harvest- life : • Respiration . • Transpiration . • Ethylene production. • Maturity process.
Respiration Factors affecting the respiration rate of FFV: Internal: • Type of tissue or organ: Leaves > fruits> roots. • Product size: bigger size< respiration rate. • Stages of development: young leaves >respiration. In fruits will depend on their classification as climacteric or non-climacteric.
Climacteric Respiration Respiración Climatérica 180 160 140 120 100 80 60 40 20 0 Cherimoya Respiration (mg CO2/Kg./Hr) Mango Prickly pear Tomate time
No-Climacteric Respiration 30 20 10 0 Strawberry Grape Respiration (mg CO2/Kg./Hr) Cherry Lemon Time
Classification NO-CLIMACTERIC Carambola Egg-Plant Lemon Orange Watermelon Pineapple CLIMACTERIC Avocado Mango Guava Plantain Banana Papaya Apple
Rep. Rhythm. Mg CO2/Kg./Hr 5 - 10 mg 10 - 20 mg 20 - 40 mg 40 - 60 mg Respiration rate Low Moderate High Very High PRODUCT Sugar beet, garlic, onion, watermelon, citrus. Cabbage, carrot, cucumber, mango, tomato. Avocado, cauliflower, lettuce, strawberry. Artichoke, broccoli, spinach, parsley, sweet Corn.
Perishability rate. PERISHABILITY INDEX Very high High Moderate Low Very low POTENTIAL LIFE (WEEKS) < 2 weeks 2 - 4 weeks 4 - 8 weeks 8 - 16 weeks > 16 weeks PRODUCTS broccoli, cauliflower, blackberry, strawberry avocado, pineapple, celery, tomato lemon, watermelon mango, potato, onion, apple, garlic, pear nuts, dried fruits.
Respiration Factors affecting the respiration rates: External: • mechanical damage and product’s sanitary condition. • temperature. • atmosphere composition (< Oxygen and CO2< respiration; > ethylene > respiration). • physical barriers (waxes, plastic films, etc.)
Mechanical damage during the postharvest chain • the temperature - affects the degree of response/ • severity of mechanical damage. • Compromise natural barriers -increasing • water loses and pathogenic infections. Impact Respiration Ethylene Time
Temperature effects on respiration rate. • At temperatures above the optimum, the rate of deterioration increases 2 to 3 fold for every 10ºC rise in temperature. • High temperature-increases the transpiration rate. 30ºC 20ºC Respiratory rhythm 10ºC Time
Transpiration • Loss of water, as vapor, from the product’s area exposed to the air, throughout the cuticle, lenticels, stomas, etc. It depends on: Internal factors: • species and variety. • type of tissue. • integrity and sanitary product condition.
Transpiration External factors: • Relative Humidity (<RH> transpiration). • Temperature (> temperature> transpiration) • Air movement (increase the transpiration rate). • Altitude (higher altitude< transpiration). • Physical barriers (avoid air contact with the product-reduce transpiration rate).
Ethylene production • Climacteric fruits are sensitive to ethylene-produce larger quantities of ethylene in association with their ripening- (auto catalysis). • No climacteric fruits produce very small quantities of ethylene. At high concentration produce degreening and increase the metabolism. • Leafy vegetables are highly sensitive to Ethylene (withering and yellowing )
Ripening Process • Physiological process that occur at the cellular level. After finishing the anabolic process, a series of catalytic reactions start –degradation of: chlorophyll, aromas, organelles and finally causing cellular collapse/death. Post-harvest technology: to delay as long as possible, the tissue disintegration/senescence phase
Fruit ripening • Loss of chlorophyll (undesirable in veg.) • Production of carotenoids and antocianines. • Starches conversion into sugars. • Changes in organic acids, proteins and fats. • Reduction in tannins and fungistatic compounds.
Natural fungistatic compounds. Unripe Ripened Interior 100% 100% 0% 0% Exterior
To reduce and delay the action of the internal factors that are responsible for product deterioration Avoid the negative effect of external factors Post-harvest Quality maintenance
Reducing product respiration rates Temperature control. • Product protection from sun heat (full sunlight) after harvesting. • Pre-cooling treatments to remove field heat. • Refrigeration. • Maintaining the cold chain.
Temperature • Key factor affecting product deterioration rate. • is the most effective tool for extending the shelf life of fresh horticultural commodities. • Key effect on spores germination and pathogenic growth.
Temperatures above or below the optimal range, can cause product deterioration due to: • Freezing. • Chilling injury. • Heat injury. TºC
Temperature Freezing: • Freezing point of perishable commodities is relatively high (ranging from -0.3 ºC y -0.5 º C). • Freezing produces an immediate collapse of tissues and total loss of cellular integrity. • A result of inadequate design of refrigerator or failure of thermostats.
Temperature Chilling Injury: Some commodities (mainly tropical and sub- tropical) respond unfavorably to storage at low temperatures well above their freezing points, temperatures called the chilling threshold temperature or lowest safe temperature.
Temperature Heat injury: Direct sources of heat can rapidly heat tissues to above the thermal death point of their cells, leading to localized bleaching or necrosis or general collapse.
Cooling Objective: to remove the field heat. Movement of the caloric energy from the product to the cooling substance.
Temperature Cooling methods
Temperature Cooling speed • Commercial cooling reaches up to 7/8 the final temperature. • First hours are crucial. • Additive effect of low temperatures. Temp. Time
Storage and refrigerated transport Cooling rooms and refrigerated vehicles…. • well designed and adequately equipped. • resistant floors. • perfectly insulated. • with adequate and well-positioned doors for loading and unloading. • allow effective distribution of refrigerated air. • allow monitoring and temperature control.
Storage and refrigerated transport • refrigerated coils surfaces designed to adequately minimize differences between the coil and air temperatures. • proper air spaces between pallets and room walls to ensure proper air circulation. • monitoring temperature (product rather than air temperature).
Storage and refrigerated transport • transit vehicles must be cooled before loading the commodity. • avoid delays. • when mixing several products: product’s ethylene and chilling injury sensibility must be considered. • appropriate packing (air circulation and reducing mechanical damage)
reducing transpiration rates Relative humidity management. Is the moisture content (as water vapor) of the atmosphere, expressed as a percentage of the amount of moisture that can be retained by the atmosphere at a given temperature and pressure without condensation. RH can influence water loss, decay development, incidence of physiological disorders, and uniformity of fruit ripening.
RH ranges • Fruits: 85-95% of RH. • Dry products: onion and pumpkin. 70-75% de RH. • Root vegetables: carrot, radish. 95-100% RH.
reducing transpiration rates • Adding moisture (sprays, steam) • Regulating air movement and ventilation in relation to the produce load in the cold storage room. • Maintaining temperature of the refrigeration coils within about 1ºC of the air temperature. • Providing moisture barriers that insulate walls of storage room and transit vehicles. • Adding polyethylene liners in containers and using perforated polymeric films for packaging.
reducing transpiration rates • Curing. • Waxes and others surface coatings . • Polymeric films for packing. • Avoiding physical injuries. • Adding water to those commodities that tolerate misting with water.