Thursday, June 22, 2023

Freezing injury

Both freezing injury and chilling injury are low temperature injuries, but for freeze damage to occur, the product must be below its freezing point.

Freezing injury results when ice crystals form in the tissues of fruits or vegetables. It is damage that occurs to plant tissues when temperatures are below 32 °F (0 °C). Pure water freezes at 32 °F, however, water in plant tissue has dissolved salts (ex. plant sap), which freezes at temperatures a few degrees below 32 °F.

Freezing temperatures can damage plants by rupturing plant cells as ice crystals form and rapid changes in temperatures occur. Freezing injury may take place in a few hours and in spots or throughout the commodity. Tissues injured by freezing generally look as if they were soaked in water.

Freezing injury symptoms include tissue browning, blackening, wilting or curling of leaves and stems. It is important to take note that younger plant tissue is more vulnerable to freezing than more mature tissue.

Refrigeration (cooling) is the total process of reducing the temperature of a food and maintaining that temperature during storage, transport, and retailing. Rapid freezing prevents undesirable large ice crystals from forming throughout the product because the molecules do not have time to form into the characteristic six-sided snowflake.

Slow freezing creates large, disruptive ice crystals. During thawing, they damage the cells and dissolve emulsions.
Freezing injury

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