Abstract

The frame of catfish is considered as waste and should be utilized maximally in order to meet the zero-waste fishery industry. Protein isolation using a pH-shifted methods was applied by adjusting the pH of fish frame to be either 3 or 12. Thereafter, the soluble proteins were recovered by centrifugation and lyophilization to be powder denoted as acid protein isolate and basic protein isolate. Characterization of these proteins powder reveal that basic protein isolate had higher water holding and fat binding capacities than that did by acid protein isolate. The solubility of both protein powders in water was observed comparably. However, solubility of acid protein isolate was higher than basic protein isolate, when 0.6 M NaCl was used as the solvent. The secondary structural changes were clearly noticed on the FT-IR, especially at the amide band (I, II, and III). The acid protein isolate and BPI solution were incorporated in filming solution constituted of gelatin. The film substituted with acid protein isolate exhibited higher in thickness and solubility than another one. However, basic protein isolate incorporation in gelatin film could improve tensile strength as well as water vapor permeability. The results suggested that isolation of protein from catfish frame could be possible by pH-shifted method and isolated protein could be used to produce edible film, especially gelatin film.