Protecting Horticultural Commodities
Fruits and vegetables and other horticultural products begin to age and deteriorate from the time of harvest.
Many factors must be considered and managed properly to ensure the produce arrive in optimum condition.
The shelf life of horticultural commodities depends on these key factors:
- Pre-shipment consideration
- Ethylene production
- Water loss
Fruits and vegetables continue to live and breathe after harvest - consuming oxygen, generating heat and giving off gases such as carbon dioxide and moisture.
This process, known as respiration, uses up a plant's resources and causes changes that influence food value, flavor, quality, color, texture and water content.
All fruits and vegetables have different respiration rates (see table below), which is part of the natural ripening process. Commodities such as potatoes and onions, enter into a dormant state when harvested and they have low respiration rates. Other commodities such as broccoli and asparagus, which are harvested during an active phase of growth, have high respiration rates and conversely, products with short post-harvest life have relatively high respiration rates.
Relative respiration rates of selected commodities
||Dates, dried fruits, nuts
||Apples, citrus fruit, garlic, grapes, kiwifruit, onions, potatoes (mature), sweet potatoes
||Apricots, bananas, cabbage, carrots, cherries, fogs, lettuce, mangoes, nectarines, peaches, pears, peppers, plums, potatoes (immature), tomatoes
||Avocados, blackberries, cauliflower, lima beans, raspberries, strawberries
||Artichokes, Brussels sprouts, cut flower, green onions, snap beans
||Asparagus, broccoli, mushroom, peas, spinach, sweet corn
Optimum storage and transit temperature is the most important factor that affects the shelf life of perishables. As a general rule, for every 18°F (10°C) increase in temperature, the rate of deterioration increases by two to three folds. Low temperature prolongs perishable commodities' shelf life because respiration, ethylene production and water loss are minimized which result in the delay of ripening and senescence (aging) of produce. If temperatures are too high, decay occurs. However, temperatures that are too low may also damage perishables, as it will cause freezing or chilling injury. Susceptibility to chilling injury is variable and affects produce originating in the tropics or subtropics.
Exposure to high temperatures
Temperature is the biggest factor in the deterioration of harvested commodities. Not only does it influence the rate of respiration, the production of ethylene and the growth of disease-forming organism, it also affects the physiological state of the product.
For example, exposure to direct sunlight or excessively high temperatures can cause uneven ripening, excessive softening, desiccation and other problems commonly referred to as heat injury. Preventing heat injury requires careful temperature management, precise monitoring and pre-transit and in-transit handling procedures.