Fish sarcoplasmic protein replaces chicken protein to make a naturally enticing and digestible cat food

For global net-zero targets, recycling of sarcoplasmic proteins from the surimi processing industry, which are typically considered biomass waste, can promote green and low-carbon processing of surimi and achieve energy conservation and emission reduction. This study investigates the effects of replacing chicken protein with silver carp (Hypophthalmichthys molitrix) sarcoplasmic protein in cat food on the feeding behavior and evaluates its digestibility. In this research, H. molitrix sarcoplasmic proteins were recovered using pH-shifting and chitosan-flocculation methods analyzed for amino acid composition and flavor. These proteins were then used as a substitute for chicken breast, combined with butter and other excipients to formulate cat food. Single-factor experiments were conducted using baking time, baking temperature, potato starch addition, H. molitrix sarcoplasmic protein addition, and butter addition to score the finished products. Response surface methodology was employed to determine the optimal process conditions for cat food production. Finally, the basic nutritional composition, palatability, and pepsin digestibility of the sarcoplasmic protein-enriched cat food were compared with two commercially available extruded puffed and low-temperature baked cat foods that have high sales volumes and positive ratings. The results showed the optimal process conditions for 100 g of cat food were as follows: H. molitrix sarcoplasmic protein addition of 22.85 g, baking temperature of 80 °C, baking time of 8.07 h, butter addition of 9.22 g. H. molitrix sarcoplasmic proteins were found to be rich in amino acids, particularly lysine (7.21 g/100 g). They also contained high levels of flavour-enhancing amino acids, such as glutamic acid (9.59 g/100 g) and aspartic acid (9.22 g/100 g), with taste activity values of 959.00 and 307.33, respectively. Additionally, high odour activity values of nonanal (24 640) and octanal (1 514), which impart a fishy flavour, significantly contributed to the overall flavour of the cat food, making it highly attractive to cats and serving as a natural food attractant. The study demonstrated that H. molitrix sarcoplasmic protein can effectively replace chicken protein. Moreover, the digestibility of cat food enriched with sarcoplasmic protein 94.07%, which was higher than that of the two commercial cat foods tested. This ingredient that H. molitrix sarcoplasmic protein is an ideal protein ingredient for replacing chicken in cat food preparation. This research provides a valuable reference for the application of H. molitrix sarcoplasmic proteins in pet food.