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BACKGROUND: Fish processing waste could be valorized by recuperating the nutrients for human consumption. Employing a suitable process would address the pollution problems associated with its dumping and would contribute to food security. In this study, protein isolates obtained from rohu (Labeo rohita) processing waste through the pH shift process (pH 13.0) were valorized through incorporation into pangasius (Pangasius pangasius) mince sausages (0.0, 50, 100, 250, and 500 g kg −1 ). These sausages were analyzed for their proximate composition, and their physical and eating quality.RESULTS: Increasing the isolate content (11.57% to 16.14%) in sausages increased their protein content and whiteness values (P < 0.05). At 250 g kg −1 level, the cooking yield was maximum, and the expressible fluid content of paste was minimum. Moreover, adding rohu protein isolates in pangasius mince increased the expressible moisture and decreased its folding and gel strength values (P < 0.05). The gel strength values were highest for the sausages without isolates (2648.67 g cm). In contrast, in the sausages containing 250, 100, and 500 g kg −1 isolate, the values were determined to be 847.88, 731.21, and 611.06 g cm, respectively. Replacing pangasius mince with rohu protein isolates had a non-significant effect on the sensory attributes of the sausages.CONCLUSION: Replacing pangasius mince with rohu protein isolates at 250 g kg −1 resulted in superior quality sausages compared with other levels tested. Incorporating rohu protein isolates in fish sausages improved the nutritional value without significantly reducing their eating quality. The findings of this study indicate promising potential for developing nutrient-rich foods using fish protein isolates.

BACKGROUND Proteins recovery using hydrochloric acid (HCl) in acid‐aided solubilization could cause greater loss in its functionality over alkali‐aided solubilization. Moreover, using HCl in edible foods is also a health concern. Replacing HCl with organic acids for acid‐aided solubilization could address these problems. The aim was to study the effect of organic acid (glacial acetic acid) as a replacement for HCl during pH shift processing on the characteristics and functionality of rohu (Labeo rohita) protein isolates. Rohu proteins were obtained by solubilizing at pH 3.0 and pH 11.0 using glacial acetic acid and sodium hydroxide (10 mol L−1). RESULTS Results showed that solubilization at pH 11.0 gave higher protein yields (766.8 ± 2.4 g kg−1) compared to solubilization at pH 3.0 (735.7 ± 7.1 g kg−1) (P < 0.05). Isolates from acid‐aided solubilization had higher whiteness and total pigment content over isolates obtained by alkali‐aided solubilization. Rohu isolates recovered by alkaline solubilization showed higher water and oil holding capacity, gel strength, folding scores, foaming and emulsion capacity than acid processed isolates (P < 0.05). Solubilization of rohu proteins using glacial acetic acid produced isolates with low breaking force (149.0 g), low storage modulus (G′) values and low folding test score (1.0) over the alkaline isolates (P < 0.05). CONCLUSION Results indicated that, recovering rohu proteins using organic acid (glacial acetic acid) could produce isolates with poor functional properties, while using the organic acid to precipitate the proteins solubilized by alkali‐aided processing could produce proteins with better yields and functionality. © 2019 Society of Chemical Industry

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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 conditions 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.