MICROWAVE DIGESTION OF PROTEINS

The time needed for a conventional acidic digestion of peptide bonds i n proteins with 6 N HCl was reduced from 18-24 h to 2 h when microwave s were applied. The rate-determining step of the splitting of the pept ide bonds depends on the amino acid composition of the proteins. Myogl obin, lysozyme and bovine serum albumin were tested as pure model prot eins. The amino acid contents determined after ion-exchange HPLC and p ostcolumn derivatisation with ninhydrin correlated well with values ob tained on the basis of known amino acid sequences. Tryptophan, methion ine as well as cysteine/cystine were partly or completely destroyed un der the hydrolysis conditions applied. Almost 95% of the thermolabile amino acids (based on theoretical values) could be recovered. The cond itions were further applied for the hydrolysis of food proteins like c asein, commercially available whey proteins as well as pea proteins, a nd a comparison with the results of the conventional hydrolysis (24 h) was made.