Flavor improving effects of cysteine in xylose-glycine-fish waste protein hydrolysates (FPHs) Maillard reaction system.

A promising way to utilize fish by-products is to develop hydrolysis of fish proteins with enzymes. The obtained fish protein hydrolysates (FPHs) are rich in peptides and amino acids, but bitterness and aroma defects impede further utilization of FPHs. The present study adopted Maillard reaction to improve FPHs' flavor and illustrated the role of cysteine in this system. We investigated the impact of cysteine (0, 0.25%, 0.5%, 0.75%, and 1%) on the browning intensity, free amino acids (FAAs), molecular weight distribution, structure of MRPs, volatile compounds changes and organoleptic characteristics of xylose-glycine-FPHs Maillard reaction systems. Results showed that the addition of cysteine lowered the browning degree of Maillard reaction products (MRPs) by inhibiting the cross-linking of small peptides and reducing the production of melanin. GC-MS and GC-IMS analysis indicated that cysteine inhibited the formation of furans and nitrogen-containing compounds and facilitated the formation of sulfur-containing compounds contributing to the meaty flavor. Sensory analysis revealed that 0.25-0.75% range of cysteine increased the meaty, caramel, umami, mouthfulness and salty notes, and caused a decrease in bitter taste of the MRPs as confirmed by GC-MS. A highly significant correlation between the organoleptic characteristics and physicochemical indicators of MRPs was found by Mantel test. These results elucidated the influence of cysteine on the formation of Maillard reaction products and will help improve the flavor profile of meat flavorings.