| Summary: | Frozen storage has long been used as a means to slow down the microbial and enzymatic degradation of fish. Unfortunately, over time frozen fish will lose protein solubility and water holding capacity leading to declining quality. To minimize the degradation of frozen fish, cryoprotectants (often a blend of sucrose and sorbitol) are employed. Although successful in limiting protein denaturation and aggregation, sugar based cryoprotectants are not suitable for diabetics or those who dislike sweet tasting fish products. A possible alternative is fish protein hydrolysate (FPH). Current knowledge on the use of FPH as a cryoprotectant, however, is limited. It is necessary to determine how FPH production parameters can be optimized for cryoprotection. It is also necessary to determine the optimal dosage of FPH in fish mince, and how FPH affects the taste of frozen fish products.
In this study, response surface methodology was used to optimize processing variables, namely pH, % enzyme/substrate, and hydrolysis time for production of cryoprotective FPH. The optimization study revealed higher cryoprotective efficacy in all 20 FPH samples produced according to a central composite rotatable design compared to a sucrose/sorbitol cryoprotective blend; however, there was little difference among FPH samples. Based on these findings, it is suggested to produce FPH with 1% enzyme/substrate, 1-hour hydrolysis and no pH adjustment because these are the most economical conditions within the central composite rotatable design. FPH produced at the suggested conditions was added to cod fish mince at levels of 2, 4, 6, and 8 percent (w/w). Evaluation of expressible moisture, cook loss, salt extractable protein, and differential scanning calorimetry profiles showed no significant difference between unfrozen and freeze/thawed fish mince samples when containing at least 4 percent FPH. Sensory evaluation by trained panelists showed that the addition of FPH into fish ball products increased the fishiness, saltiness, bitterness, and firmness while decreasing the level of moistness. Panelist comments suggested a taste preference of fish products containing FPH over fish products containing sucrose/sorbitol. Based on the cryoprotective effectiveness and taste acceptability of FPH, it can be concluded that FPH is a viable alternative to sugar based cryoprotectants. === Land and Food Systems, Faculty of === Graduate
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