[Very low temperature (quick freezing) and pseudo-stabilization of the chemical composition of food of plant origin].

The consequences of freezing at -18, -30 degrees C are presented: slowing down or acceleration of enzymatic or non enzymatic reactions, concentration effect, consequences of the death of cells, (time--temperature relation). The most characteristic examples of nutritive value adulterations are presented: ascorbic and dehydroascorbic acids, other vitamins, derivatives of the insaturated fatty acids oxidation, changes in proteins. Other damages more related to sensorial quality are summarized: "chlorophyll, phenolic substances, aroma, pectins. These chemical changes occurring at low temperatures are generally less important than the losses in nutritional value of frozen plant products related to the necessary treatments preceding or following cold storage. Particularly, the losses during blanching and thawing (drip) are discussed. Finally, quick freezing as it is used now industrially does not exactly stabilize the nutritive quality of plant products but protects this quality satisfactorily. Progress is however possible, concerning the cold treatments (storage temperature lowering) and especially the losses before and after freezing and storage (blanching, transport, distribution, thawing).