Characterisation of hydrolysate for identifying initial peptide cleavage site of kappa-casein by milk coagulating Wrightia tinctoria serine proteases

摘要

Research on identifying vegetable milk coagulants has gained momentum in the past few decades. Extent of casein hydrolysis and specific initial hydrolytic site on x-casein are considered crucial in deciding suitability of plant proteases for cheese making. In the present study, three phase partitioned (TPP) proteases (serine) of Wrightia tinctoria stem were assayed to understand their specific cleavage site on x-casein. Time dependent analysis of x-casein hydrolysis by W. tinctoria proteases revealed 2 min incubation to be enough for hydrolysis to begin. Molecular mass of the resulting major peptide was confirmed to be 14,542.52 Da and was further characterised using LC/ESI-MSMS. The initial site of hydrolysis by W. tinctoria proteases on x-casein was Asn123-Thr124, which is different from the expected Phe105-Met106 of rennin. The study concludes that even with its unique initial site of x-casein hydrolysis, W. tinctoria proteases could influence milk clotting probably with distinct organoleptic properties. (c) 2020 Published by Elsevier Ltd.