Production of Iron-Binding Peptides from Colostral Whey by Enzymatic Hydrolysis

Abstract

Colostral whey prepared from colostrum (pooled from first six post-partum milkings) was heated for 10 min at <TEX>$100^{\circ}C$</TEX> Heated colostral whey was incubated with 1% enzymes (protein equivalent basis) for 15, 30, 60, 90, and 120 min at <TEX>$50^{\circ}C$</TEX>. Papain, pepsin, trypsin, and alcalase produced different degrees of hydrolysis (DH), 10.66%, 12.42%, 10.83%, and 25.31%, respectively, at an incubation time of 120 min. The SDS-PAGE reveals that significant amounts of bovine serum albumin (BSA), <TEX>${\beta}$</TEX>-lactoglobulin (<TEX>${\beta}$</TEX>-LG), and <TEX>${\alpha}$</TEX>-lactalbumin (<TEX>${\alpha}$</TEX>-LA) survived papain digestion. In contrast, pepsin completely removed BSA but not <TEX>${\beta}$</TEX>-LG present in heated colostral whey. Alcalase completely eliminated BSA, <TEX>${\beta}$</TEX>-LG, and <TEX>${\alpha}$</TEX>-LA. This differential hydrolysis was confirmed by reversed-phase HPLC analysis. Using ion-exchange chromatography, fraction-1 (F-1) was obtained from alcalase hydrolysate at a NaCl gradient concentration of 0.25 M. Reversed-phase HPLC chromatograms of alcalase F-1 showed numerous small peaks, which probably indicate that a variety of new peptides were produced. Iron content of alcalase F-1 was 28.94 ppm, which was the highest among all enzyme fractions, whereas iron content of colostral whey was 36.56 ppm. Main amino acids contained in alcalase F-1 were Thr (15.45%), Glu (14.12%), and Ser (10.39%). Therefore, alcalase can be used to generate good iron-binding peptides in heated colostral whey, and the resulting iron-binding peptides could be suitable as a value-added food ingredient for food supplements.