Freezing is one of the oldest and most commonly used means of food preservation. It has
been known to be an extremely effective means of preserving food for extended periods
since Paleolithic and Neolithic times, when man used ice and snow to cool food. The cooling
effect of salt and ice was ﬁrst publicly discussed in 1662 by the chemist Robert Boyle, but
this technology was certainly known in Spain, Italy and India in the sixteenth century.
9 Cooling and freezing
The storage life of fish or meat, or of a fish or meat product, depends on the acidity and water content of the product. External influences such as oxygen (from the air), micro-organisms, storage temperature, light and water secretion
Antifreeze proteins (AFPs) are produced by many species of teleost fish
that inhabit potentially lethal ice-laden seawater and afford them protec-tion from freezing. To date type I AFPs have been fully characterized in
two teleost orders: Pleuronectiformes and Scorpaeniformes.
The recent discovery of a large hyperactive antifreeze protein in the blood
plasma of winter flounder has helped explain why this fish does not freeze
in icy seawater. The previously known, smaller and much less active type I
antifreeze proteins cannot by themselves protect the flounder down to the
freezing point of seawater.
There are other bizarre and unkind ramifications. For example, the transport of POPs
depends on temperature; in a process known as the "grasshopper effect", these chemicals
jump around the globe, evaporating in warm places, riding the wind and particles of dust,
settling to Earth in cool spots, and then vaporizing and moving on again. As the POPs move
away from the equator they encounter cooler climates with less evaporation. The result is a
general drift of these pollutants toward the Poles and mountain areas.