Study On Changes Of Yuba Quality During Film Formation And Preparation Of Yuba Powder

Yuba is tradition soybean food of China with a long history. It contains abundantnutrition, including isoflavones, phospholipids etc. and it·s deeply loved by consumers. Theproduction of Yuba is mainly based on experience controlling and the quality is not stable.Moreover, the start of production is from soaked soybeans, the process is relatively long, thereare a lot of organic waste water and sludge in the process, great pressure is on theenvironment. For these problems, the changes of Yuba quality and its mechanism werestudied in the traditional production process, the influence of soy protein denaturation andaggregation degree on the quality of Yuba were also researched, and soy protein as rawmaterial to Yuba production process were studied. All these efforts were hoped to providesome theory reference for Yuba·s massive production, to maintain the taste and nutritionalvalue and to develop a clean, green, environmentally friendly production at the same time.In this paper, the eating quality of Yuba was chosen as the research object, three indexesincluding mechanical properties (strength of extension and elongation at break), reconstitutionproperties and color of Yuba were studied. The main research contents in this paper is asfollows:At first, physicochemical properties changing of soybean milk and Yuba in traditionalcourse of processing were studied. Result showed the main constituent of soybean milk andYuba had significant changes even if soybean milk came from the same pot. Due to theevaporation of water, concentration of the three main components in soybean milk becamehigher and higher. However, the total solids content of protein decreased from53.49%to48.66%, the total solids content of carbohydrates increased from23.05%to28.51%, the totalsolids content of lipid ratio changed smallest. According to the removing order of Yuba,protein content decreased from60.48%to53.3%, carbohydrate content increased from14.87%to18.2%and there was only little change in lipid content. Meanwhile, the mechanicalproperties of Yuba decreased from3.3kg/cm2to1.38kg/cm2, the color of it became darkbrown, but rehydration properties of it gradually increased and it became difficult to formYuba in the late period of film forming. Through a deep analysis, it shows these phenomenahave a close relationship with the protein component in soybean milk and Yuba and theMaillard reaction.By studying the denaturation degree of soybean protein·s effect on the quality of Yuba itfound that the higher the degree of soybean protein denaturation, the higher the mechanicalproperties of Yuba was, and the shorter the rehydration time was, and the color of Yuba wasalmost without change. Soybean protein was preheated by an enzyme reactor at85℃and thethermal aggregates were formed, as a result, the mechanical properties of Yuba was increased,the rehydration time was reduced, and there was almost no change in color. After theinstantaneous ultra-high temperature heating process, soybean protein can form large amountof effective aggregates. This way of heating can not only improve the mechanical propertiesof Yuba, but can also significantly reducing rehydration time, and improve Yuba·s color at thesame time. High quality of Yuba and Yuba powder products can be produced by using soy proteinIsolate. Research indicated that with an appropriate amount adding of soybean oil (1.8%) andsucrose (1.6%) into soy protein isolated solution, Yuba with the best quality was produced anda production technology was established on the base of it. In this research, Yuba prepared bysoy protein and special protein powder, compared with traditional Yuba, it has betterreconstitution properties, although there is some shortage, the difference is very little and italmost possesses the same quality with some commercial products.