|
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 . 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. 〔 Da-Wen Sun (2001), Advances in food refrigeration, Yen-Con Hung, Cryogenic Refrigeration, p.318, Leatherhead Food Research Association Publishing, http://www.worldcat.org/title/advances-in-food-refrigeration/oclc/48154735 〕 Flash freezing techniques are also used to freeze biological samples fast enough that large ice crystals cannot form and damage the sample. This rapid freezing is done by submerging the sample in liquid nitrogen or a mixture of dry ice and ethanol. 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.〔("Quick-Frozen Food Exactly Like Fresh." ) ''Popular Science Monthly'', September 1930, pp. 26-27.〕 This process was further developed by American inventor Daniel Tippmann〔http://www.google.com/patents/US20110107784〕 by producing a vacuum and drawing the cold air through palletized food. His process has been sold and installed under the trade name "QuickFreeze" 〔http://www.tippmannengineering.com/quickfreeze〕 and enables blast freezing of palletized food in 35% less time than conventional blast freezing.〔http://www.gcca.org/cold-facts/cover-story-innovation-on-display.html〕 ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Flash freezing」の詳細全文を読む スポンサード リンク
|