The Study Of Crispness Of Frozen Pre-fried Coated Food For Microwave Oven

The frozen fried coated food will lose crispness after microwave heating due to moisture migration from the inner food base to the outer breading. The research was focused on solving the crispness problems and to develop new microwave able products mainly through selecting the suitable formulation of the coating and also changing the process conditions.Firstly to establish a reasonable crispness evaluation system after correlate analyses of sensory test and penetrometry test ,and decided to select sensory test value as the main test index. Then we studied the influence to the crispness of food with different food additives such as soybean protein, soybean phosphatide, dextrin, xanthic gum, CaCl₂, oil and crumb and found all ingredients increased the crispness, but soybean phosphatide and CaCl₂ can not exist at the same time ,so we use Ca-bind soybean protein to replace SPI .Finally we selected the soybean protein, soybean phosphatide, dextrin, xanthic gum as the main effective factors. After the Orthogonal Experiment and Response surface methodology analyses of such factors, we got to know the optimum composition of the coating batter was Ca-bind soybean protein 5.85/100g, soybean phosphatide 1.85-2g/100g, dextrinl.85-2g/100g, Xanthic gum 1g/100g.The research also studied the effect of inner Aw, and frozen storage condition and microwave heating on the crispiness, water content and temperature of products. The results showed that when the freeze rate reached 0.058 ℃/S or more and the storage temp, is lower than -40 ℃ ,it will lead to good crispness. The determination of microwave station showed that for a product of 30g, it shall need the 30S heating of 600w which will contribute to the good texture.The e ffects o f various a dditives on crispness were explained by film theory, free volume theory of food macromolecule. The WVP value o f optimized complex film was 46.6% lower than the parallel protein film. The determination by DSC indicated that the optimized-coating components could evidently improve Tg value of the system. The SEM analyse results showed the optimized coating was firmer and smoother than the basic coating, which contributed to the good water-resistant capacity.