Research On The Processing And Preservation Of The Seasoning Dried Soy Bean Curd

Seasoning dried bean curd is the reprocessing products of the bean curd, salty withdelicacy, and rich in nutrition. It’s perishable easily just because of its rich nutrition, so thehigh pressure and temperature sterilization methods were always adopted to preserve the beancurd, under which the quality of the bean curd changed obviously. The procedures ofprocessing the soybean curd also affected the quality of the bean curd significantly, so theproblem to improve the quality of the soy bean curd was always paid close attention to. Thisthesis optimized the processing and preservation technology of the bean curd to improve itsquality and guarantee its shelf life. These studies will provide the academic basis for thepotential industrial production of the seasoning dried bean curd.Firstly, the processing: i.e. crossing the alkali, marinating, air drying of the bean curd were studied,and the microorganisms of the processing were controled. The optimal concentration gained by orthogonalexperiment of crossing the alkali process was0.3%, temperature was93°C and time was2min. The effectsof addition of sodium chloride and sorbitol on the Aw and quality of the products was studied, theconcentration of sodium chloride and sorbitol was3%and6%, respectively. Then the effects of differenttemperatures and time of the air drying process on the quality and Aw of the bean curd was studied,95°C(40min) was the best drying parameters; In the processing control of microorganism, the ultravioletgermicidal irradiation was adopted to reduce the initial bacteria content of the products. The Aw of the finalproducts was0.825, the moisture content was45%.Secondly, in order to control the microbes and keep quality, the effect of different sterilization ways onthe quality and microbes of samples were studied. The pasteurization at80°C、90°C、100°C werestudied first, the final pasteurization parameters was100°C-25min. Then the915MHZ low frequencymicrowave equipment was studied under their suitable power and sterilization time, and the results showedthe uniformity and effects of the intermittent microwave sterilization1050W(3min-1min-3min) was best.Finally in order to improve the uniformity of the915MHz low frequency microwave sterilization further,we adopted the intermittent microwave sterilization unite with boiling water sterilization, compareddifferent sterilization methods and conditions:①no sterilization;②intermittent microwave sterilization;③intermittent microwave sterilization unite with boiling water sterilization100°C-5min;④intermittentmicrowave sterilization unite with boiling water sterilization100°C-10min;⑤the boiling watersterilization100°C-25min;⑥high temperature and high pressure sterilization121°C-20min on theeffects of products. The results showed the sterilizing effects of the high temperature and high pressuresterilization was best, but the effect on the quality of the products was worst; the intermittent microwavesterilization had good sterilizing effect because of its heating effect and bactericidal effect, and the effect onthe quality of the products was best; the sterilizing effect of the intermittent microwave sterilization unitewith boiling water sterilization is better, and has less effect on the quality of the products. So we choose the915MHz low frequency intermittent microwave sterilization1050W(3min-1min-3min) unite with boiling water sterilization100°C-5min based overall consideration.In order to predict the shelf life of the seasoning dried bean curd, the Gompertz equationwas used to fit the microbial growth under room storage conditions. The shelf life of productsat room temperature was168days. The various qualities of products had better storagestability during room temperature storage.