The Preparation And Application Of Organic Acid Coagulant By Yellow Serofluid Fermentation

In this experiment, yellow serofluid (a by-product of tofu) is used as a raw material, organic acid coagulant fermented by yellow serofluid. Total acidity is raised and it gives tofu a unique milk flavor. RP-HPLC was built to simultaneous determination of7organic acids such as citric acid, malic acid, tartaric acid, oxalic acid, fumaric acid, amber acid and lactic acid in yellow serofluid. Analysis on composition and content of organic acids in the yellow serofluid; This paper mainly studies culture conditions of yellow serofluid fermented by Lactobacillus and process conditions of application of organic acid coagulant.Agilent Eclipse XDB-C18is used as the solid phase(4.6mm×150mm,5μm); detection at210nm; mobile phase methanol:0.01mol/L KH2PO4-H3PO4buffer solutions (3:97,pH-2.85); flow rate of0.8mL/min; column temperature is25℃; sampling volume of20μL. Under the optimal chromatographic conditions, seven types of organic acids can quickly separated. The results showed that linear correlation coefficient r>0.9824, detection limits of0.5558-1.2948μg, relative standard deviation of0.13%-4.2%. According to linear regression equation,seven organic acids content are calculated by this method. There were high content of oxalic acid, citric acid, succinic acid and tartaric acid in yellow serofluid, reached to39.87μg/mL49.15μg/mL、22.94μg/mL、19.36μg/mL,respectively. The content of lactic acid is14.73μg/mL, the content of malic acid is3.235μg/mL, the content of boletic acid is0.4322μg/mL, the content of total acid is149.70μg/mL.The influences of lactic acid content were investigated by initial pH, lactose content, fermentation time culture temperature and inoculate quantity. Orthogonal experiment was used to optimize carbon source and its fermentation condition. The optimize culture conditions of organic acid coagulant were showed as follows:lactose content1.5%, initial pH=6.5, inoculate quantity6%, culture temperature37℃, fermentation time84h. The lactic acid content under these conditions was5.1g/L. Under the above process conditions, the rate of production, hardness, cohesiveness and protein content were196.43%,419.15g,261.42gs and9.62%respectively. Lactic acid content was increased and function of coagulant was improved by compare with other methods, protein content of tofu was also increased, and gives tofu a unique milk flavor.On the basis of high performance liquid chromatography, organic acids in fermentation liquid were determined, the content of lactic acid is252.7p.g/mL,17times higher than before, the content of total acid is406.8μg/mL.The processing technology of tofu was studied by single factor and response surface optimization experiments. The result shows that:additive level of coagulant is20.5%、 concentration of coagulant is63.48%、 water:bean=7.58:1,under such conditions the rate of tofu production is196.43%, the hardness of tofu is419.15g, the content of protein in tofu is9.62%and its quality is good.Using high performance liquid chromatography and analysis of seven organic acids in yellow serofluid of tofu, this method is simple, sensitive, accurate and reproducible. Suitable for analysis of organic acids in the yellow serofluid. Study on the culture conditions of Lactobacillus fermented yellow serofluid and process conditions of application of coagulating agent can move up the value of using yellow serofluid and provides foundation data for research on coagulant agent of organic acid.