Mechanisms of Food Additives, Treatments, and Preservation Technology 29513°C, although certain temperate commodities are also susceptible to chilling injury.
The symptoms often cannot be detected at low temperatures and become visible
several days after removing to warmer temperatures. The extent of damage depends
on the length of exposure and temperature. The approximate lowest safe storage
temperatures for selected fruits and vegetables are given in Table 10.1.
When produce is subjected to freezing temperatures between 0 and –2°C the
water inside the cells starts to freeze. The ice may cause damage in tissues. Frozen
produce has a water-soaked or glassy appearance. Other changes that usually occur
may not be visible while the product is frozen, but during thawing the mechanical
destruction of cellular membranes allows contact between enzymes and substrates.
This results in enzymatic spoilage such as browning reactions and lipoxygenase
oxidation. The damage is often associated with losses of juice and microorganisms
present on the surface of fruits and vegetables easily contaminate exudates. Although
a few commodities are tolerant to mild freezing, generally it is advisable to avoid
such low temperatures because subsequent storage life is shortened. Produce that
has recovered from freezing is highly susceptible to decay. When fresh produce isTABLE 10.1
Susceptibility of Fruits and Vegetables to Chilling Injury at Low
but Nonfreezing Temperatures^
Commodity
Approximate Lowest Safe
Temperature (°C) Chilling Injury SymptomsAubergines 7 Surface scald, Alternaria rot
Avocados 5–13 Grey discoloration of flesh
Bananas (green/ripe) 12–14 Dull, gray-brown skin color
Beans (green) 7 Pitting, russeting
Cucumbers 7 Pitting, water-soaked spots, decay
Grapefruit 10 Brown scald, piking, watery breakdown
Lemons 13–15 Pitting, membrane stain, red blotch
Limes 7–10 Pitting
Mangoes 10–13 Grey skin scald, uneven ripening
Honeydew melon 7–10 Pitting, failure to ripen, decay
Watermelon 5 Pitting, bitter flavor
Okra 7 Discoloration, water-soaked areas, piking
Oranges 7 Pitting, brown stain, watery breakdown
Papaya 7 Pitting, failure to ripen, off-flavor, decay
Pineapples 7–10 Dull green color, poor flavor
Potatoes 4 Internal discoloration, sweetening
Pumpkins 10 Decay
Sweet peppers 7 Pitting, Alternaria rot
Sweet potatoes 13 Internal discoloration, pinking, decay
Tomatoes: Mature green 13 Water-soaked softening, decay
Tomatoes: Ripe 7–10 Poor color, abnormal ripening, Alternaria rot
Source:Lutz, J.M. and Hardenburg, R.E., The Commercial Storage of Fruits, Vegetables and Florist and
Nursery Stocks, U.S. Government Printing Office, Washington, DC, 1968, p. 1.