Effect Of Coagulant And Pulping Process On Quality Of Whole Soybean Curd

Tofu was one of the main ingredients in Chinese cuisine.It had abundant vegetable protein and the reputation of"plant meat".In recent years,numerous researches had found the processing of whole soybean curd could avoid the loss of nutrients such as dietary fiber,polyunsaturated fatty acids,calcium,and carbohydrates destroyed by the emission of bean dregs in the production of traditional tofu,which remained the nutrition of tofu.In this research,a native soybean cultivar Gongqiu 8 was used as raw material.By investigating the pulping process and solidification process of tofu could provide basic data and theoretical reference for the development of compound coagulant and the production of tofu.The parameters of solidification process and different pulping process were optimized by combining response surface with principal component analysis during dry process-superfine grinding,ultrasonic disruption and enzymatic hydrolysis of cellulose.The main results were as follows:1.The solidification process of whole soybean curd was studied.The single factor test showed that addition of GDL had significant effect on the hardness,adhesiveness,chewiness,gel strength,water retention rate and sensory quality of whole soybean curd,addition MgCl₂ had great effect on other parametersin addition to the sensory quality and addition T-Gase had obvious effect on the hardness and gel strength but had no significant effect on other parameters?P<0.05?.The results of response surface experiment showed that addition GDL had the greatest influence on the gel strength,followed by the addition of MgCl₂ and TG enzyme.The optimal coagulant proportionfor making whole soybean curd was:0.5%GDL,0.07%MgCl₂,and 0.02%T-Gase and under this condition,the gel strength of whole soybean curd was 185.956 g.Comparing with the traditional tofu produced by single coagulant,the whole soybean curd by compound coagulant had higher hardness,gumminess,chewiness,gel strength,and sensory quality.Besides,more uniformed and compacted and uniformed net structure was formed at this optimal condition with the observing of scanning electronic microscopy.2.The influence of pulping process of superfine grinding,ultrasonic and cellulase hydrolysis on the hardness,gumminess,chewiness,gel strength,and water retention rate of whole soybean curd was studied,and the parameters of pulping process had been optimized by response surface combining with principal component analysis.During pulping process of superfine grinding,the optimal comminution time was 9min,frequency was 25 Hz,and water/powder ratio was 6:1.Under this condition,the gel strength,gumminess and chewiness of whole soybean curd were 145.920 g,64.060,and 61.728,respectively.Comparing with comminution frequency and other factors,water/powder ratio had most significant effect on comprehensive evaluation index of whole soybean curd and there was no interaction effect for each factor.During pulping process of ultrasonic disruption,the optimal ultrasonic time were 9 min,ultrasonic power was 150 W and water/powder ratio was 5.5:1.Under this condition,the gel strength,gumminess and chewiness of whole soybean curd were 189.068 g,84.181,and 81.840,respectively.In all factors,the water/powder ratio had most significant effect and the ultrasonic time had minimal effect,in which the interaction of ultrasonic power and water/powder ratio had a significant influence on the comprehensive evaluation index.During pulping process of cellulase hydrolysis,the optimal reaction time were 35min,temperature was 45°C,and the additive amount of cellulose was 9 U/g.Under this condition,the gel strength,gumminess and chewiness were 160.902 g,76.268,and 71.127,respectively.The reaction temperature had most significant effect and the additive amount of cellulose had minimal effect,and there was no interaction effect for each factor.3.At the significant level of P=0.05,tofu prepared by different pulping processes such as different chrominance,texture,protein content and water retention was significantly different.In the three methods,the texture characteristics,protein content and water retention rate of tofu prepared by ultrasonic-pulverization were the best,followed by ultra-pulverizing and cellulose enzymatic pulping process,and the tofu made by traditional pulping process was worst.From the chrominance of tofu,the tofu produced by traditional process was the best,followed by the ultra-micro-pulverization the ultrasonic pulverization and cellulase enzymatic pulping process.At the significance level of P=0.05,the sensory quality of tofu prepared by ultra-pulverizing pulping process was little different from okara-free tofu,and was superior than cellulase enzymatic and ultrasonic pulverization pulping process.In conclusion,tofu produced by superfine grinding pulping process had the best quality compared with pulping process of enzymatic hydrolysis of cellulase and ultrasonic disruption.