Oxidation of sarcoplasmic proteins during processing of Cantonese sausage in relation to their aggregation behaviour and in vitro digestibility.

The physicochemical changes of sarcoplasmic proteins, especially oxidation behaviour, were measured to determine their mechanism of action on in vitro protein digestibility during Cantonese sausage processing. The results indicated that carbonyl level increased (p<0.05) during the process. The fluorescence loss of tryptophan residues was a direct consequence of the oxidative degradation. All the parameters of protein aggregation were highly (p<0.05) correlated with carbonyl level and protein surface hydrophobicity (H(0)), indicating that protein oxidation and thermal denaturation could induce protein aggregation, leading to secondary structural changes. The analysis of in vitro digestibility showed no correlation between pepsin activity and protein oxidation, due to the biphasic response of sarcoplasmic proteins toward proteolysis. However, a highly significant (p<0.05) correlation was observed with trypsin and α-chymotrypsin activity, indicating that protein oxidation induced the changes in H(0), protein aggregation and secondary structure, which further influenced in vitro digestibility.