Abstract: Tenebrio molitor rennet (TMR) was prepared and the effects of preheating milk at different temperatures on its coagulation behavior and hydrolytic properties were evaluated, and the structure of milk curds was characterized by Fourier transform infrared (FTIR) spectroscopy and laser scanning confocal microscopy (LSCM). The results showed that the water-holding capacity of curds increased significantly with the increase in preheating temperature (P < 0.05), while the particle size, apparent viscosity and storage modulus G′ increased initially and then decreased (P < 0.05); the particle size and apparent viscosity reached their maximum of 15.07 and 0.51 at 45 ℃, respectively. The production of casein glycomacropeptide (CGMP) and the degree of hydrolysis (DH) were not significantly changed with increasing temperature from 45 to 55 ℃ (P > 0.05). The secondary structure and microstructure indicated that the flexibility, stability and compactness of curds were the best at 45 ℃. At this temperature, the water-holding capacity and whey OD value of TMR-coagulated curd tended to be stable when compared with that coagulated by commercial rennet (CR), and the particle size significantly increased. Meanwhile, TMR-coagulated curd exhibited a continuous, irregular and compact network structure, indicating good coagulation properties. Therefore, the optimum coagulation temperature for TMR was 45 ℃. This study provides a theoretical basis and reference for the development and application of new insect-derived rennet.

Key words: Tenebrio molitor; rennet; coagulation behavior; hydrolysis properties; infrared spectroscopy; microstructure