Parameter optimization of preparation technology of fried whole-soybean tofu

Abstract: Fried tofu, a kind of most popular Chinese traditional food, wins many consumers with its delicate soft taste and crisp skin. In addition to taste, the nutritive value of fried tofu is also one of the reasons for the popularity of soybean products. Okara contains a wealth of dietary fiber, protein, fat, soy isoflavones and other nutrients. But, in the processing of the traditional soybean products, a lot of okara was excluded, which results in the waste of resources and pollution to the environment. Whole soy products, by using all the ingredients of whole grains of soybeans (without waste), can improve the yield and nutritional value and reduce environmental pollution. At present, the study of domestic and foreign scholars on the whole soybean products is mainly concentrated in the whole bean tofu, whole bean drinks, and whole bean sufu. Fried tofu as reported at home and abroad is very rare. Patent reports of tofu production process are based on traditional tofu processing methods, which use the wet treatment to remove the tofu residue and then fry the tofu. The research on the fried whole-soybean tofu has not been reported yet. In this experiment, the processing of traditional tofu was improved to achieve tofu made by whole soybean grain, improve the utilization rate of raw materials of soybean products and maximize the nutritional content of soybean. On this foundation, fried tofu was made by whole soybean grain through the frying process, which filled the vacancy of fried soybean products. In this experiment, whole soybean was used as raw material to study the preparation process of new fried tofu. At first, the technological conditions of enzymatic hydrolysis of whole-soybean milk were studied, and the effects of enzyme dosage, enzymolysis time and temperature on enzymatic hydrolysis were investigated in order to obtain the optimum conditions of enzymatic hydrolysis, and the enzymatic hydrolysis process was optimized using response surface methodology. Moreover, the effects of frying technology (frying time and frying temperature) on the color, oil content and texture of fried whole-soybean tofu were studied by using sensory evaluation. Then, the composition of the fried whole-soybean tofu was measured. The results showed that the optimum conditions of enzymatic hydrolysis were as follows: enzyme addition of 0.53%, hydrolysis temperature of 50 ℃, and enzymolysis time of 160 min, and under the optimal conditions hydrolysis degree of insoluble dietary fiber was the highest, and the content of reducing sugar was 2.9433 mg/mL. The whole-soybean tofu fried in 170 ℃ for 4 min showed the excellent sensory quality and the sensory score was 95. Under the conditions, its lightness, redness and yellowness were 60.22, 10.85 and 37.80, respectively. The oil content was 15.6%, and the hardness was 2 972 g. Finally, the contents of traditional tofu, whole-soybean tofu, fried whole-soybean tofu were compared. The contents of total flavonoids and total phenolics in whole-soybean tofu and fried whole-soybean tofu were higher than that in traditional tofu, the nutritional content of fried whole-soybean tofu was improved, and the total flavonoids content increased by 14.53% and 7.93% and the total phenolics content increased by 18.95% and 82.11%, respectively, compared with the former 2 kinds of tofu.