Controlled proteolysis of food protein ingredients.

can be divided into three groups, which correspond to fractions separated by gel chromatography having mol.wts. of 15 000, 60000 and 100000. The activity of proteolytic enzymes in barley and malt was historically measured with protein substrates such as haemoglobin, casein, gliadin, gelatin or with synthetic substrates including N-substituted peptides. Since proteolytic activity is influenced by the amino acid sequence of the substrate as well as by its tertiary structure, it is better to use hordein, the natural substrate. Detail of proteolytic degradation during brewing is best followed by considering the important stages in the process: malting, mashing, wort boiling and maturation. Active proteolysis during fermentation mainly occurs within the yeast cell. The complexity of intercellular transformations relevant to different yeast strains is so complex that it could easily justify a separate lecture and has had to be excluded from these discussions.