Flash freezing

Flash freezing refers to the process in various industries whereby objects are quickly frozen by subjecting them to cryogenic temperatures, or in direct contact with liquid nitrogen at -196°C.

Flash freezing is used in the food industry to quickly freeze perishable food items (see frozen food). In this case, food items are subjected to temperatures well below water's melting/freezing point. The freezing process results in ice crystals formed from intra- and extracellular water, and subsequent crystal growth. The freezing speed directly influences the nucleation process and ice crystal size. Decreased growth of the initially formed ice crystals is a result of a high heat removal rate and causes an increased rate of nucleation. Smaller, more ubiquitous ice crystals cause less damage to cell membranes. ^[1]

Flash freezing techniques are also used to freeze biological samples fast enough that large ice crystals cannot form and damage the sample.^[2] This rapid freezing is done by submerging the sample in liquid nitrogen or a mixture of dry ice and ethanol.^[3]

A supercooled liquid will stay in a liquid state below the normal freezing point when it has little opportunity for nucleation; that is, if it is pure enough and has a smooth enough container. Once agitated it will rapidly become a solid.

American inventor Clarence Birdseye developed the quick-freezing process of food preservation in the 20th century.^[4]

This process was further developed by American inventor Daniel Tippmann^[5] by producing a vacuum and drawing the cold air through palletized food. His process has been sold and installed under the trade name "QuickFreeze" ^[6] and enables blast freezing of palletized food in 35% less time than conventional blast freezing.^[7]

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