Injuries

Certain injuries to produce can occur during refrigerated storage under suboptimal conditions and include those due to chilling, freezing, or ammonia. Chilling injury usually occurs to commodities of tropical origin at temperatures below 10-13°C (50-55.4°F), although certain temperate commodities are also susceptible (13-15). Table 2 lists some commodities susceptible to chilling injury and their symptoms. Often symptoms cannot be detected at low temperatures and only become visible several days after the commodity has been removed to warmer temperatures. The extent of damage depends on length of exposure and chilling temperature. It may occur in a commodity exposed a short amount of time to a temperature considerably below the danger zone, but not if it is exposed longer to a higher temperature in the danger zone. Also, chilling injury may be cumulative, and chilling during transit or in the field before harvest may add to the effects of storage chilling. Chilling injury has been reduced by treatments such as intermittent warming, temperature preconditioning, controlled atmosphere or hypobaric storage, waxing, and film packaging.

Freezing injury occurs when ice crystals form in produce tissues, and is manifested by a mushy, limp, and water-soaked appearance. The extent of freezing injury depends on exposure time and temperature and varies with different commodities.

Ammonia injury occurs when ammonia escaping from direct-expansion refrigeration units come in contact with the commodity. Injury is evident as brown to greenish black discoloration of the outer tissues and, in severe cases, as discoloration and softening of inner tissues (16). Daily

Table 2. Commodities Susceptible to Chilling Injury and Their Symptoms

Lowest safe temperature

Commodity (°C) Symptoms

Avocados 4.5-13.0 Grayish brown flesh discoloration Dull color when ripe Pitting, surface decay Pitting, decay

Surface scald, Alternaría rot, black seeds Pitting, red blotch Sheet pitting, Alternaría rot on pods and calyxes, seed blackening Browning, sweetening Water soaking, softening, decay

Table 1. Methods of Cooling for Different Commodities

Cooling method

Commodities cooled

Hydrocooling Asparagus, cantaloupes, celery, cucumbers, green peas, peaches, peppers, radishes Vacuum cooling Asparagus, artichokes, broccoli, Brussels sprouts, cabbage, cauliflower, celery, endive, escarole, head lettuce, parsley, spinach, sweet corn Air cooling Cauliflower, cucumbers, grapes, melons, peppers, strawberries, tomatoes Icing Broccoli, Brussels sprouts, cantaloupes, carrots, green onions, kale, radishes

Bananas Cantaloupes Cucumbers Eggplants

Lemons Peppers

Potatoes Tomatoes, ripe

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