Recovery of proteins from grouper (Epinephelus diacanthus) filleting waste was done using isoelectric solubilization method. During the isolation, influence of process variables such as; temperature, ratio of solvent and homogenate, pH, time of centrifugation and speed of centrifugation on protein yields was studied. It was observed that the homogenate to solvent ratio, centrifugation speed protein recoveries. For isolating the proteins from grouper waste using pH shift process the optimum

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... tions found were; pH-11.0 in alkaline range, pH 3.0 in acidic range, 120 min extraction time, homogenate to solvent ratio of 1:6 and centrifugation speed of 10000 rpm. During the pH shift processing of grouper proteins myoglobin, total pigments and lipid content of proteins were reduced by 90.77, 70.79 and 82.69%, and 93.91, 79.59 and 82.04%, in alkaline and acidic extraction process, respectively. A significant increase in the lightness and whiteness values of the isolates was observed as compared to the raw material. Protein isolates obtained using acidic solubilisation process were found to be whiter than alkali-aided protein isolate.