Studies On Effects Of Soybean Species On North Tofu Quality And Methods Of Evaluation In North Tofu

Tofu becomes main consumption form of soybean not only in eastern countries but also in western countries with healthy diet consciousness enhancing. There are many kinds of soybean in our country. Researches of correlations between soybean species and tofu quality were few. And there were contradictions in results. At present, there was no basis for choosing soybean species to process tofu and no quality classification standard of tofu, which became bottleneck of tofu enterprises industrialization. In this article, 24 soybean species were chosen to process north tofu with MgCl2 as coagulant and basic compositions of soybean, yield, water retention, texture indexes, nutrition indexes, color and sensory evaluation were tested. Relationship between soybean compositions and north tofu quality indexes and the correlations between sensory indexes and instrumental analysis indexes were studied by correlation and regression analysis. And regression equations were established. Then Soybean varieties which were fit to process North tofu were chosen by cluster analysis. Basis for selecting soybean species and north tofu quality classification standard were constructed. The results were meaningful to improve soybean processing quality and important to choose soybean species, increase tofu yield, improve tofu quality. And theoretical basis were provided to establish comprehensive evaluation system of tofu quality.Main results as follows:(1) There were big differences of protein, water-soluble protein, fat, phytic acid, ash, starch, 7S protein and 11S protein in different soybean species.(2) Protein, water-soluble protein, 11S protein content in soybean were positively correlated to wet yield, dry yield and water retention of north tofu. Phytic acid was positively correlated to wet and dry yield of north tofu. 7S protein was positively correlated to water retention of north tofu. Protein, water-soluble protein, 11S protein and phytic acid content in soybean were negatively correlated to hardness of north tofu. Ash content in soybean was negatively correlated to chewiness of north tofu. Protein, water-soluble protein, 11S protein and phytic acid content in soybean were positively correlated to protein content of north tofu. Fat content in soybean was positively correlated to fat content of north tofu. Ash content in soybean was positively correlated to ash and calcium content of north tofu. Obtained F value and correlation coefficient R of regression equations were significant.(3) Hardness in sensory evaluation was positively correlated to hardness and chewiness of texture analyzer. Taste was negatively to chewiness. Color in sensory evaluation was positively correlated to b* value and negatively correlated to L* value. Hardness and chewiness of texture analyzer were negatively correlated to general acceptability. L* value was positively correlated to general acceptability. Obtained F value and correlation coefficient R of regression equations were significant.(4) Zhengyin soybean and Zheng 94059 which were fittest to process north tofu were selected by cluster analysis.(5) Basis using protein, water-soluble protein, phytic acid and 11S protein as indicators for selecting soybean species when north tofu processed was constructed. Also north tofu quality classification standard using yield, water retention, hardness, L* value, protein, fat and general acceptability was constructed.