| Instant soybean curd powder is a kind of soybean powder, which can be dissolved rapidly in hot water and turned into soybean curd in a few minutes when the coagulations are added. Because instant soybean curd powder is convenient,nutritious,safe and sanitary, it has a good development prospect.The paper researched the technics of Instant soybean curd powder. In the course of soaking, the water temperature was generally at 20-30℃and in the course of grinding, the material to water ratio was generally 1:10 to 1:15. The optimal excellent gel properties could be obtained by the heat treatment at 95℃for 10 minutes. Moreover, by the change of viscosity we deduced that the assemble state of soybean protein molecule was different, at the same time it can be well defoaming when added 0.5% monoglyceride during the course of heating. By comparing the emulsifying properties, we selected six polyglycerol fatty acid esters and hydrophilicity monoglyceride as emulsifier, and their compound ratio is 1:2. According to the sensory index of soybean powder, the optimum process parameters of spray drying was slurry concentration 16%,inlet air temperature at 180℃and outlet temperature at 80℃.Different kind of coagulants and concentration both had an effect on soybean protein gel, in which salt—coagulant especially effected by pH value. The optimum concentration,temperature,pH and concretionary rate of different coagulants were: GDL, 0.5%, 90℃, 7min; CaCl2, 0.15%, pH value 6.5, 3min and CaSO4, 0.5%, 90℃, pH value 6.4, 5min. Using carrageenan as the wall material to embed the calcium chloride, the optimum entrapment ratio was 1:1.5.The paper researched on the effect of pH value,species and concentrations of ion on soybean protein solubility. At low pH, the taste of soybean powder was a little acid; however, at high pH, when pH value above 10, the soybean powder would make out a very ill taste. As Na+ ion, it could accelerate the dissolution of soybean protein at low concentration; contrary to Ca2+ ion, it would block the dissolution of soybean protein with the increased concentration of Ca2+.The solid content of soybean milk had an effect on the soybean protein in the course of heating. DSC was used to measure the denature enthalpy and denature temperature of 7S and 11S globulin of different solid content. The conclusion was that with the increased solid content of soybean milk, the denature temperature was rised.The different drying methods also had effects on the soybean protein denaturation. Spray drying effected greatly on the secondary structure of the soybean protein. Compared with spray drying, freeze drying was mild, soybean protein denaturation could be maintain at a certain degree, so the gel properties were improved. Moreover, the soybean protein could be protected by added hydrophilic surface—active agent in, because it can rise the denature temperature.In this paper, we studied preliminarily the effects of ultrasonic—modification and microware—modification on the products. We found that under the proper condition, the solubility and gel properties of the products had both been enhanced. Moreover, we detected the effect of modification on sencondary structure of soybean protein by FT—IR and also observed the microstructure of soybean powder by SEM founding soybean powder with good solubility all had porous in their surface.
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