Flash freezing
Encyclopedia
Flash freezing refers to the process in various industries whereby objects are quickly frozen by subjecting them to cryogenic
temperatures.
For example, 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
(32°F or 0°C), causing the water inside the foods to freeze in a very short period of time without forming large crystals, thus avoiding damage to cell membranes.
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 early 20th century.
Cryogenics
In physics, cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures. A person who studies elements under extremely cold temperature is called a cryogenicist. Rather than the relative temperature scales of Celsius and Fahrenheit,...
temperatures.
For example, flash freezing is used in the food industry to quickly freeze perishable food items (see frozen food
Frozen food
Freezing food preserves it from the time it is prepared to the time it is eaten. Since early times, farmers, fishermen, and trappers have preserved their game and produce in unheated buildings during the winter season. Freezing food slows down decomposition by turning water to ice, making it...
). In this case, food items are subjected to temperatures well below water's melting/freezing point
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
(32°F or 0°C), causing the water inside the foods to freeze in a very short period of time without forming large crystals, thus avoiding damage to cell membranes.
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
Liquid nitrogen
Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...
or a mixture of dry ice
Dry ice
Dry ice, sometimes referred to as "Cardice" or as "card ice" , is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue...
and ethanol.
A supercooled liquid will stay in a liquid state below the normal freezing point when it has little opportunity for nucleation
Nucleation
Nucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form by way of nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by 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
Clarence Birdseye
Clarence Frank Birdseye II was an American inventor who is considered the founder of the modern method of freezing food.- Early work :...
developed the quick-freezing process of food preservation in the early 20th century.
See also
- VitrificationGlass transitionThe liquid-glass transition is the reversible transition in amorphous materials from a hard and relatively brittle state into a molten or rubber-like state. An amorphous solid that exhibits a glass transition is called a glass...
- supercoolingSupercoolingSupercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid....
- Snap freezingSnap freezingSnap freezing is the process of cooking meals until they are almost done and then rapidly chilling them....
- Blast chillingBlast chillingBlast chilling is a method of cooling food quickly to a low temperature that is relatively safe from bacterial growth. Bacteria multiply fastest between +8 °C and +68 °C...