The Suitability Evaluation Of Different Soybean Materials In Tofu Making

The yield and quality of tofu are determined by the physical and chemical properties of soybean. During machining process of different soybean materials, the quality of the products makes significant differences. Currently, a large number of the domestic and foreign studies have shown that the physical and chemical properties of soybean materials have a close relationship with the quality of tofu. However, due to the differences of the sample and sample size adopted by different researchers, the conclusions obtained are inconsistent, or even contradictory, the main reason for which may be the complexity of tofu-making technologies. At present, a lot of problems about the impacts on the quality of tofu of the soy material have not been resolved, and there are no criteria to guide the production of tofu. Therefore, whether the staffs of tofu processing or soybean breeders have not yet scientifically predicted and evaluated the quality of tofu processing on the basis of certain physical and chemical indicators of soybean. In this experiment, by measurements of soybean components(kernel weight, volume, density and grain protein, oil, moisture, phytic acid, a water-soluble protein content, protein subunit composition and their proportion) and various indicators of tofu(milk yield, protein content and tofu protein, moisture content, water retention, hardness, adhesiveness, springiness, cohesiveness, chewiness and resilience, sensory evaluation), we aim to analyze and explore the correlation between raw materials of different soybeans and the quality of tofu processing, establishing an evaluation system of soybean raw materials and physical and chemical indicators of soybean and the processability of tofu, providing the oretical basis and technical support for the standardization of soy products, the screening of special varieties of tofu and the processing of industrial tofu. The results are as follows:(1) There has a significant difference in soybean components content, it is ranged from 11.49 g~26.54 g for kernel weight, 5.00 m L~13.00 m L for 50 seeds’ volume, 1.02~1.22 for density, 34.36%~47.77%、18.39%~24.73%、5.79%~8.94% for protein、fat and moisture, 8.07 mg/g~15.03 mg/g for phytic acid, 27.39%~41.26% for water-soluble protein, 26.7%~50.8%、35.5%~65.0%、0.75~2.04 for 7S、11S subunit and the ratio of 11S/7S.(2) The compositions content of tofu made by different soybean materials covers a relatively wide range. The milk yield ranged from 216.2 g to 273.8 g, the protein content for milk and tofu ranged from 4.67%~6.12%、5.28%~7.50%, the tofu components ranged from 85.47%~88.43% for moisture, 78.45%~83.94% for water retention, 71.739 g~161.137 g for hardness,-142.988 g?sec~-6.891 g?sec for adhesiveness, 0.761~0.945 for springiness, 0.395~0.492 for cohesiveness, 23.821~60.262 for chewiness, 0.120~0.239 for resilience, 5.1-7.7 for overall acceptability in sensory evaluation.(3) The hundred-grain weight of soybean has a significant negative correlation with the springiness of tofu and a significant positive correlation with the resilience of tofu; the volume of soybean has a very significant negative correlation with the springiness of tofu and a very significant positive correlation with the resilience of tofu; the grain density of soybean has a significant negative correlation with tofu cohesiveness, a very significant negative correlation with the protein content of soy milk, the water retention of tofu and the resilience of tofu, but a very significant positive correlation with the springiness of tofu; the protein content of soybean has a significant positive correlation with the protein content of tofu, a very significant positive correlation with the protein content of soy milk and the moisture content and water retention of tofu; the oil content of soybean has a very significant negative correlation with the moisture content and water retention of tofu; the moisture content of soybean has a significant negative correlation with tofu adhesiveness, but a very significant positive correlation with the moisture content of tofu; the phytic acid content of soybean has a significant positive correlation with the protein content of soy milk, the moisture content and water retention of tofu, the hardness and cohesiveness of tofu; water-soluble protein content of soybean has a very significant positive correlation with the protein content of soy milk; soybean 11 S has a significant positive correlation with tofu cohesiveness; soybean 7S has a significant negative correlation with tofu cohesiveness; soybean 11S/7S has a significant positive correlation with tofu cohesiveness; the sensory evaluation has a significant positive correlation with the chewiness and a very significant positive correlation with the hardness of tofu.(4) The 7(Shanxi), 8(Shanxi), 17(Hebei jing county) were more suitable for processing of tofu among the selected 25 of soybean materials.