大豆分离蛋白(Soybean protein isolate,SPI)对外界环境的变化极其敏感,中和工段中pH值微小的变化就会改变蛋白质的结构和功能性质.通过添加NaOH调控凝乳的pH值,利用红外光谱和内源荧光光谱分析SPI的结构及功能性质,研究发现在中性条件下SPI具有较好的起泡性,碱性条件时SP1具有较好的乳化性,当体系pH值为7时,SPI的起泡性最佳,当体系pH值为8.5时,SPI的乳化性最佳.建立了 25 L大豆SPI中和工段pH值精细调控体系,利用Matlab模拟生产过程,通过动态线性与静态非线性拟合,采用模糊自适应控制结合Wiener模型调控中和罐的加碱量,当将中和罐中pH值调控为7时,调节时间为37.4 s,生产的SPI起泡性指数为57.22％,将中和罐中pH值调控为8.5时,调节时间为33.4 s,生产的SPI乳化活性指数为69.35 m2/g,体系无超调量用碱.
Effect of pH Value on Functional Properties of Soybean Protein Isolate and Its Precise Regulation
Soybean protein isolate(SPI)exhibits remarkable sensitivity to environmental changes,particularly alterations in pH value during the neutralization process.Even minor fluctuations can have a profound impact on the structure and functional properties of the protein.Revolving around the addition of NaOH to regulate the pH value of the curd,and analysis of SPI's structure and functional attributes was done by using infrared and endogenous fluorescence spectra.It was revealed that SPI displayed excellent foaming properties under neutral conditions,while its emulsification capabilities excelled under slightly more alkaline conditions.Specifically,pH value of 7 yielded the best foaming type,while pH value of 8.5 led to superior foaming properties alongside optimal emulsification.In order to fine-tune the neutralization of a 25 L soybean SPI section,a pH value control system was established,and the entire production process was simulated by using Matlab.Dynamic linear and static nonlinear fitting techniques were employed,with a combination of fuzzy adaptive control and the Wiener model utilized to regulate the amount of alkali added to the neutralization tank.The adjustment time of 37.4 s achieved when the pH value in the neutralization tank was set to 7.Likewise,at pH value of 8.5,the adjustment time remained efficient at 33.4 s,while the SPI emulsion activity index reached 69.35 m2/g.Notably,the system successfully avoided any overshooting of alkali during the process,ensuring precise control and stability throughout.To summarize,the research emphasized the significance of pH value control during the neutralization of soybean protein isolate.The findings can provide important insights into optimizing SPI's structure and functional properties,which can have significant implications for its applications in the food and industrial sectors.
soybean protein isolatepH valuefunctional propertiesfuzzy controlWiener model
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