Amino acid composition and anti‐polyphenol oxidase of peptide fractions from sericin hydrolysate

Summary Sericin hydrolysate (SH), prepared from enzymatic hydrolysis of sericin, was investigated for its antipolyphenol oxidase (PPO) properties. SH decreased PPO activity from both purified mushroom PPO and extracts from apple and eggplant, and retarded browning in fresh‐cut apple and eggplant. SH was a competitive inhibitor using catechol as a substrate. SH exhibited copper ion‐chelating power and reducing power abilities. Fractionation of SH using size exclusion chromatography resulted in four fractions, designated as F1, F2, F3 and F4, with PPO inhibition of 35.75%, 3.89%, 24.52% and 14.75%, respectively. Ser and Asp were major amino acids found in F1. Amino acid sequences in F1, as investigated by LC‐MS/MS using de novo sequencing, contained a high ratio of amino acids with chelating ability. Moreover, amino acids with reducing power ability and with antityrosinase ability were also identified in the sequences. Preparation and study on properties of peptide fractions from sericin hydrolysate.