Studies on Roasting Changes of Proteins

Changes of casein and lysozyme during roasting at various times and temperatures 100 ~ 300°C), especially those in amino acid composition and formation of some nonvolatile degradation products, were investigated.

Tryptophan, methionine, basic amino acids and β-hydroxy amino acids were easily decomposed as compared with acidic amino acids and other neutral amino acids in casein and Iysozyme. In hot water extract of roasted casein were detected some free amino acids, peptides, organic acids such as α-ketoglutaric, tartaric and malic acids, and indole. It is considered that free amino acids are produced mainly through ionic cleavage of peptide bond with the water bound within casein.