Technology to increase the crispness of pre-fried spring-roll by microwave reheating using soy protein isolate film

The mechanism and molding condition of soy protein isolate film were investigated in order to improve the crispness of pre-fried spring-roll after freezing and reheated with microwave, which was strongly affected by the moisture immigration outward. The parameters of soy protein film-forming were studied with single-factor and orthogonal experiments, and the optimized results were soy protein isolate 40 g/L, glycerol 15 g/L and transglutaminase(TG) 1.5 g/L. Observed by Scan Electron Microscopy(SEM), the spring-roll coated with the protein film was revealed to be more smooth, tighter and less interspace compared with its counterpart without film, as well as be more able to resistant against moisture immigration. Furthermore, the temperature profile of film-coated spring-roll in microwave reheating was studied. It show that the film-applying of soy protein isolate can distinctly increase the capacity of microwave-absorbing and shorten the temperature difference between the outer and fillet, which can also save heating time by microwave and lead to good crispness of reheated spring-roll.