Physicochemical and Sensory Evaluation of Cookies Supplemented with Protein Isolate from Tilapia (Oreochromis niloticus) By-products

Abstract

The present study evaluated fish protein isolate (FPI) recovered from tilapia (Oreochromis niloticus) frame by-products as a protein-enriching ingredient in cookies. Tilapia frames were processed using the pH-shift method, and the recovered FPI was incorporated into cookie formulations by replacing refined wheat flour at 10%, 20% and 30% levels. The isolate showed a yield of 12.5% and contained 84.23% protein, 4.72% fat, 2.74% ash, 4.48% moisture and 3.83% carbohydrate. FPI incorporation significantly influenced the nutritional and quality attributes of the cookies. Protein content increased from 6.95% in the control to 27.71% in cookies containing 30% isolate, while carbohydrate content decreased from 68.24% to 46.81%. Fat content, ash content, water activity, free fatty acid value, peroxide value and microbial quality remained within the reported acceptable range for the prepared products. FPI incorporation also affected physical characteristics, including thickness, spread ratio, hardness and colour values. Increasing FPI levels reduced cookie hardness and lightness while increasing redness. The water absorption index and water solubility index increased with FPI incorporation, indicating improved hydration and functional properties. Total plate count was not detected immediately after baking, indicating satisfactory microbiological quality. Sensory evaluation using a 9-point hedonic scale indicated that cookies containing 20% FPI had the best overall acceptability among the enriched formulations. The findings indicate that tilapia frame-derived FPI can be incorporated into cookies as a value-added ingredient, with 20% inclusion providing a suitable balance between improved protein content and sensory acceptability. However, long-term sensory quality and storage stability require further investigation.