Color and texture of surimi-like gels made of protein isolate extracted from catfish by-products are improved by washing and adding soy whey

Authors: CHANG, SAM - Coastal Research And Extension Center; ZHANG, YAN - Coastal Research And Extension Center

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2022
Publication Date: 6/16/2022
Citation: Chang, S., Zhang, Y. 2022. Color and texture of surimi-like gels made of protein isolate extracted from catfish by-products are improved by washing and adding soy whey. Journal of Food Science. 87(7):3057–3070. https://doi.org/10.1111/1750-3841.16229.
DOI: https://doi.org/10.1111/1750-3841.16229

Interpretive Summary: Fish texture is an important food attribute and can greatly influence the commercial value and consumer acceptance of food products. Enzymes derived from the digestive tract or from endogenous fish muscle cells upon animal death lead to meat protein degradation in the isolated proteins to damage fish food quality such as gel texture in making surimi-like products. Color is another important food attribute, which greatly influences consumer acceptance and preference. Isolated proteins from catfish byproducts tended to be darker than fillet due to presence of blood proteins. Our objective is to enhance texture of fish gel products using a novel approach that was using soy whey, a by-product generated from the production of tofu and soy protein isolate. Results showed that soy whey contained trypsin inhibitors which inhibited endogenous undesirable enzymes and improved the texture of cooked fish gel products. A washing protocol was used to remove heme proteins in the isolated proteins, and resulted in substantial improvement of cooked product color. The findings from this research provided the scientific and engineering foundations that are needed for building commercial production of catfish protein from catfish byproducts for making fish-ball or fish sausage types of food products.

Technical Abstract: Protein extraction from catfish by-products has been proven economically and technically feasible. However, the gel prepared from protein isolate was dark and lacked elasticity. By-product mince washing and application of soy whey were adopted in this study to address the above gel quality issues. Heating soy whey at 75 C° for 3 min could eliminate over 99.9% lipoxygenase activity and retain more than 50% trypsin inhibitor activity. Washing by-product mince for 2 min with water-to-mince ratio of 2:1 could achieve satisfactory gel color, which was comparable to that of commercial surimi gels. When soy whey was applied, the autolytic enzyme-induced proteolysis was inhibited in a dose-dependent manner by up to 74%. With addition of soy whey, resilience, hardness at maximum force, hardness at 5 mm compression, springiness, cohesiveness, chewiness, fracturability and deformation could be increased by up to 43.10, 66.92, 36.72, 14.59, 29.17, 143.25, 93.82, and 27.97%, respectively. However, the texture was still inferior to the gel made from fillet mince. SDS-PAGE revealed that myosin was most susceptible to proteolysis and application of soy whey could effectively protect it from degradation. Different from tropomyosin, myosin and actin were greatly involved in disulfide bond formation.