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¹ Walailak University, Department of Agro-Industry, School of Agricultural Technology
² Functional Food Research Unit Thasala, Nakhon Si Thammarat, 80161, Thailand DOI : 10.4194/1303-2712-v16_1_05 Viewed : 4768 - Downloaded : 5276 The effect of acid and alkaline pH shift processes on biochemical and physicochemical characteristics of protein isolates from bigeye snapper (Priacanthus tayenus) head by-product (HB) was investigated. Approximately 30% protein yield with the significant reduction of lipid and ash (P<0.05) was obtained from both processes. However, partial denaturation of resulting isolates was noticeable in both processes as shown by the decreases in reactive SH content and Ca2+-ATPase activity (P<0.05). Acid process recovered less total pigments with lowered heme iron content resulting in a greater whiteness of the isolate (P<0.05). The highest haem-globin destruction indicated by the disappearance of a soret peak of myoglobin spectra was noticeable in the acid process. The oxidation of residual lipids in both protein isolates measured by TBARS was markedly lowered than in HB (P<0.05) even though the PV was not significantly different among treatments (P>0.05). Both acid and alkaline methods effectively removed TVB-N and fishy odour and lowered the TCA-soluble peptides from HB (P<0.05). Therefore, the pH shift processing can be used as a powerful tool to recover proteins from HB. However, properties of the protein isolate were influenced by solubilisation method. Acid process gave a protein isolate with better overall quality compared to alkaline version. Keywords : Bigeye snapper, by-product, pH shift processing, protein isolate