Optimization Of Soymilk Pulping Process And Establishment Of Soybean Nut Nutrition And Sensory Quality Evaluation System

Soybean milk is a kind of vegetable protein beverage, which is invented and developed by chinese people and has distinct characteristics in Chinese food culture. Till now, homemade soybean milk has become one of the main forms of soybean milk consumption. Nowadays, there are more and more household soybean milk machines with different brands and models, but there are no uniform standards to evaluate the pulping quality of them.In this dissertation, the quality evaluation system for the pulping quality of household soybean milk machine was established through the principal component analysis (PCA) and analytic hierarchy process (AHP) method. Firstly, single factor test and response surface analysis were used to optimize the pulping pretreatment conditions of household soybean milk machine, and the effects of wet and dry bean pulping models on the quality of soybean milk were investigated. Secondly, nine major brands of household soybean milk machines were selected, and the nutritional and sensory quality of soybean milk under same pulping conditions, the difference and correlation between the quality indexes of the 9 machines were investigated, and core indexes of nutritional quality were screened out. Based on the quantitative descriptive analysis, the evaluation method of the sensory quality of soybean milk was established and the key sensory characteristic indexes were determined. Finally, the weight of each evaluation index and the comprehensive quality evaluation system for the pulping quality of household soybean milk machine was established through PCA, AHP and questionnaire survey method. The main contents and conclusions can be summarized as follows:(1) The nutritional quality and physical property of wet and dry bean pulping model of household soybean milk machines were compared and it showed that wet bean pulping model is superior to the dry bean pulping model.The soaking time, soaking temperature and the radio of beans and water were investigated to optimize pulping conditions, optimum pulping conditions of twelve hours soaking time,25 ℃ soaking temperature and the ratio of 1:9 between beans and water were determined as the basis for the next step of data measurement.(2) Refer to standards and regular determination methods, evaluation indexes of nutritional qualities and the determination methods of soybean milk were ascertained. Through the difference and correlation coefficient analysis, the small coefficient of variation and correlation significant indexes were excluded, six core evaluation indexes including soluble protein content, fat content, reducing sugar content, soybean isoflavone content, particle size and a were ultimately selected. Physical and chemical indexes and nutritional indexes were analyzed based on the PCA method, the weight of each index was calculated according to its contribution on the total variance. The evaluation model of nutrition, physical and chemical quality of soybean milk was established as follow:Y=0.190*soluble protein content+0.198*fat content+0.189*reducing sugar content+0.163*soybean isoflavone content+0.229*particle size+0.031*a*(3) The sensory quality evaluation method of soybean milk was built based on the quantitative descriptive analysis, the method of setting up evaluation team, establishing milk sensory descriptors and making reference samples were described in detail, nine sensory indexes which can reflect the differences among soybean milk samples were ultimately determined, consisting of color, bean aroma flavor, beany flavor, cotton slip sense, consistency, astringent feeling, sense of life, beans flavor and sweet.The compare of importance between two sensory indexes were investigated by questionnaire survey, then the weight of each index was determined based on the AHP method. The evaluation model for the sensory quality of soybean milk was established as follow:G=0.075*color+0.084*bean fragrance+0.042*beany+0.167* soft and smooth+0.127*consistent+0.058*astringent+0.054* mouth coating+0.295*bean+0.098*sweet(4) The weights of nutrition, physical and chemical properties and sensory quality of soybean milk were respectively 0.645 and 0.355 which were calculated by the data of questionnaire survey, through weighted two evaluation models, the comprehensive evaluation system of pulping quality of household soybean milk machine was established as follow:F=0.123*soluble protein content+0.128*fat content+0.122*reducing sugar content+0.105*soybean isoflavone content+0.148*particle size+0.020*a*+0.027*color+0.030* bean fragrance+0.015*beany+0.059* soft and smooth+0.045*consistent+0.021*astringent +0.019* mouth coating+0.105*bean+0.035*sweetBased on the comprehensive evaluation system, nine prototypes were evaluated and comprehensive ranking was obtained, then nine prototypes were graded by centesimal system, the result suggests that prototype 2 and prototype 3 were excellent, prototype 4, prototype 5, prototype 7 and prototype 9 were good, prototype 1 and prototype 8 were middle, prototype 6 was poor.