Physicochemical properties of surimi from fish protein isolates of tilapia (Oreochromis sp.) processing wastes

Abstract

The increase in world total tilapia production would lead to the mass accumulation of by-products which are of good quality and commercial value. During the improper storage and handling of fish, sufficient time would be given for rigor mortis to occur in the fish and a drop in freshness would be duly noted. The objective of this study was to evaluate the quality of fish protein isolates (FPI) extracted from the processing wastes of red hybrid tilapia. Alkaline-aided extraction was used to extract the FPI from the processing wastes. The FPI were then analyzed during both stages: raw and cooked. Quality attributes between the freshness and type of processing parts used are studied. Parameters used for determining the quality of FPI are the yield percentage, moisture content, pH value, proximate analysis, gel strength and whiteness. The results gave yield percentage ranging between 9.3 - 15.5% for fresh FPI and a drop from 2.6 - 12.2% in yield percentage for aged FPI. The moisture content was insignificantly (P<0.05) different between fresh FPI samples but significantly (P<0.05) dropped only for aged skin FPI. Crude fat content was significantly (P<0.05) higher in skin and head part compared to the other parts and remained significantly (P<0.05) high even after aging. However, the crude protein content in fresh skin and head FPI were insignificantly (P<0.05) different compared to their aged samples while the flesh and bones FPI significantly (P<0.05) dropped after the aging process. The gel strength of fresh FPI were significantly (P<0.05) higher in the flesh, bones and head FPI compared to skin FPI but a significant (P<0.05) drop in head gel strength was observed after the process of aging. Whiteness were found to be significantly (P<0.05) different in all parts of the FPI samples but only a significant (P<0.05) drop of whiteness occurred in the skin part after aging while the other significantly (P<0.05) increase. Conventional surimi was found to have significantly better gelling properties and whiteness compared to FPI gels extracted from tilapia. However, the by-product that was closely comparable to that of conventional surimi was found to be the bones part. This conclusion was made that FPI extracted from the bone by-products gave results which are promising and showed potential to be used for the extraction of FPI in making surimi-based products.