Key Technology Of The Production Of Walnut Tofu

Because of its nutrient-rich, walnut has been payed much attention. Especially in recent years, scientists show great concern for the research of its nutritional and medicinal value. However, because the kinds of deep processing of walnut products were insufficient, new products were needed to research and develop to meet the needs of different people in the present. Tofu is a traditional Chinese food, the main raw material is soybean, its varieties of product were little, including soybean tofu, a small amount of peanut tofu, colored tofu. tofu which produce with walnut and soybean not only can rich product type, but also can play the role of nutritional supplements. In this paper, two walnut tofu, walnut and soybean as raw material, production process were researched and compared with the nutritional quality of conventional soybean tofu:(1) walnut oil and walnut meal were obtained by oil-squeezing from walnut kernel, the optimum process parameters and the optimum adding amount of walnut meal was get by studying the effect of walnut moisture content, squeezed time during the preprocessing of walnut on residual oil, soluble protein and tofu quality. The results showed that were as follows: moisture content of peeling walnut kernel of 4%, squeezed time of 15 min, the mixture of walnut meal and soybean ratio of 4:6. Finally walnut oil and walnut tofu two products were get. Add walnuts to soybean meal produced walnut tofu, tofu structure, color, and so will not cause a greater negative impact, walnuts and dried after pressing, making thicker walnut flavor, nutrition and texture is improved.(2) The influence of single factor including amount of walnuts, soy milk concentration, coagulant dosage, solidification temperature and solidification time on walnut tofu production was explored With tofu yield, sensory, texture as the index, in this basis, L9(34) orthogonal design was conducted, the optimum parameters were obtained as follow: walnut amount of 30%, the concentration of milk of 1: 7, the solidification temperature of 75℃, setting time of 25 min.(3) Compared with the physical and chemical characteristics, amino acid and fatty acid of commercial soybean tofu, the protein content of walnut meal tofu is twice as much as soybean tofu, which was 10.188%, the fat content of walnut kernel tofu was the highest among three products, which reached to 8.355%, whereas, its calcium content was less than soybean tofu. The amino acid compositions of three tofu products were analyzed by High performance liquid chromatography, the total amino content of walnut meal and walnut kernel was higher than soybean tofu’, the total amino content of walnut kernel was maximum, reaching to 10.684 mg / g. Eight essential amino acids of three tofu products respectively accounting for 50.46%, 42.95% and 42.86% of the total amino acids contents. By using WHO / FAO amino acid pattern as the standard, protein nutritional value of walnut kernel tofu was the best in three tofu products according to SRC value. According to RC value, the first limiting amino acid was leucine. fatty acids of Three kinds of tofu is mainly composed with palmitic acid, linoleic acid, oleic acid and stearic acid, which the highest content of fartty acid is linoleic acid, oleic acid followed.(4) The principal component of PCA analyzed with TS-5000 Z electronic tongue had good separation on three tofu products, which cumulative contribution rate was up to 89.426%. The aroma components in three tofu products were analyzed by SPEMGC-MS, including aldehydes, alcohols, alkanes, ketones, esters and other volatile substances, there were some differences among three tofu products. Soybean tofu, walnut meal tofu and walnut kernel tofu respectively contained 44, 51 and 40 kinds of volatile components and the walnut meal tofu’ was the most. The textures of three tofu products were detected by using the texture analyzer, there existed few difference on hardness, chewiness, elasticity between walnut kernel tofu and walnut meal tofu, both of them were significantly higher than soybean tofu.