Analysis of the non-volatile components and volatile compounds of hydrolysates derived from unmatured cheese curd hydrolysis by different enzymes

Fifteen cheese protein hydrolysates were produced by using four different proteases. Then, the free amino acids (FAAs), molecular weight distribution (MWD), electronic tongue evaluation, and volatile compounds of the corresponding products were evaluated, respectively. The results suggested that 2SD had the strongest hydrolysis characteristic, followed by 6SD and FN. Samples hydrolyzed for less than 6 h or more than 18 h contained great defects of taste. Peptides with 150 Da – 450 Da were mainly responsible for bitterness, saltiness, umami, and aftertaste in some enzyme hydrolysis. Under the same total enzyme concentration condition, the sample hydrolyzed by Flavourzyme and Neutrase for 18 h released more richness and less bitterness than the other systems, which were characterized by butter and cream odor. Notably, it was found for the first time that tetramethylpyrazine (TMP) was detected in cheese proteolysis with the highest content of 17.59 µg/g in Protease 2SD for 30 h. 2-Undecanone and acetoin played a key role in the flavor formation of the tested samples. Regarding the different chemical families of volatiles, acids were more abundant in the samples hydrolyzed by Protease 2SD and 6SD, while FN systems can achieve high ketone content.