加工条件对醇法大豆浓缩蛋白溶解性及结构的影响Effects of processing conditions on the solubility and structure of alcohol leached soybean protein concentrate

为探究工业化生产的醇法大豆浓缩蛋白溶解性较差的原因，研究了醇法加工条件（乙醇体积分数、浸提温度、干燥温度）对大豆浓缩蛋白溶解性及结构的影响。结果表明：大豆浓缩蛋白的溶解度随着乙醇体积分数的增大呈现先降低后升高的趋势，乙醇体积分数为65%时溶解度最低；浸提温度和干燥温度的升高会导致溶解度大幅降低；随着浸提液中乙醇体积分数的增大，大豆浓缩蛋白表面疏水性、分子间的疏水相互作用、二硫键含量及粒径均呈现先增加后降低的趋势，在乙醇体积分数为65%时最大，而α-螺旋含量增加，β-折叠含量整体先增加后降低，无规卷曲含量降低；随着浸提温度和干燥温度的升高，大豆浓缩蛋白分子间氢键作用力降低，而表面疏水性、分子间疏水相互作用、二硫键含量和粒径增大，α-螺旋向β-折叠及无规卷曲转变，蛋白质结构趋于无序。综上，工业化醇法加工工艺（60%~70%乙醇体积分数、50~60 ℃浸提温度、60~70 ℃干燥温度）所引发的大豆浓缩蛋白表面疏水性的增大、分子间聚集程度的增加等导致了其溶解度的降低，不利于后期应用。To explore the reasons for the low solubility of alcohol leached soybean protein concentrate in industrial production, the effects of processing conditions(ethanol volume fraction, leaching temperature and drying temperature) on the solubility and structure of soybean protein concentrate were studied. The results showed that the solubility of soybean protein concentrate showed a trend of decreasing and then increasing with the increase of ethanol volume fraction, with the lowest solubility at an ethanol volume fraction of 65%. The solubility decreased significantly with the increase of extraction temperature and drying temperature. The surface hydrophobicity, the hydrophobic interaction between molecules, the content of disulfide bond and the particle size of soybean protein concentrate increased first and then decreased, and the maximum value was when the ethanol volume fraction was 65%; the α-helix content increased, β-sheet content first increased and then decreased, the random coil content decreased. With the increase of leaching temperature and drying temperature, the hydrogen bond interaction between molecules decreased, the surface hydrophobicity, the hydrophobic interaction between molecules, the content of disulfide bond and the particle size of soybean protein concentrate increased, the α-helix changed to β-sheet and random coil which indicated that the protein structure tended to disorder. In summary, the increase of protein surface hydrophobicity, the increase of intermolecular aggregation degree and other protein structure changes caused by the industrial alcohol processing process (60%-70% ethanol volume fraction, 50-60 ℃ leaching temperature, 60-70 ℃ drying temperature) lead to the decrease of protein solubility, which is not conducive to later application.