Preparation, Amino Acid Composition, Peptide Fractionation, Thermal and pH Activity Stability of Featherback (Chitala Ornata) Skin Gelatin Hydrolysate with Zinc-Binding Capacity

Abstract

This research serves as an initial exploration into a novel zinc carrier derived from gelatin obtained from the skin of featherback fish (Chitala ornata), which is a natural source. The skin was found to contain approximately 63.23 ± 0.51 % moisture, 71.18 ± 1.82 % crude protein, 9.13 ± 3.40 % crude lipid, and 19.69 ± 1.61 % ash (on a dry weight basis). To extract the gelatin, warm water was used, followed by hydrolysis using Alcalase. The gelatin-to-water ratio was 1:4 (w/v), with a pH of 8, temperature of 50 °C, enzyme-to-substrate (E:S) ratio of 40 U/g protein, and a hydrolysis time of 4 h. The resulting hydrolysate exhibited a degree of hydrolysis (DH) of 18.46 ± 1.35 % and a zinc-binding capacity (ZnBC) of 39.66 ± 1.56 % (which was 2.00 times lower than that of ethylenediamine tetraacetic acid disodium salt (Na2EDTA)). The hydrolysate's activity remained above 60 % even after exposure to a wide pH range 1-11 and treatment for 180 min at 100 °C. Notably, the hydrolysate contained a significant amount of hydroxyproline (Hyp), measuring 1550 mg/L. Ultrafiltration was utilized to fractionate the hydrolysate, resulting in five peptide fractions (>30 kDa, 10-30 kDa, 3-10 kDa, 1-3 kDa, and