Some aspects of protein changes in frozen foods.

In the past decades many results on changes of food proteins caused by freezing and their relation to quality changes were found. Recently especially the nutrition physiological viewpoint of these alterations has aroused considerable interest. In the present paper the attempt is made to outline some aspects of these changes which are usually referred to as "denaturation" caused by freezing. After a description of the phenomena observed and their measurement, a survey of the main causes presumed for the "denaturation" of fish muscle proteins by freezing is given. With special consideration of the molecular range it can be said that generally aggregation phenomena prevail and that the participating molecules, or part of them, may still be native or more or less changed in their conformation before or during aggregation. Definite judgement of the nutritional properties of the altered proteins in frozen foods is possible only when convincing results of feeding experiments will be available.