蛋白溶解度作为评定豆粕过熟程度指标的研究

Protein Solubility as an Indicator of Overprocessing of Soybean Meal

本实验以南苑植物油厂本经加热的生豆粕为原料，用高压蒸锅在108℃，0．294kg·cm(-2)压力下处理0，12，20min，以及在121℃，0．882kg·cm(-2)压力下处理5，20，40，60min和原样品共得到八种不同加热程度的豆粕，进行脲酶活性（PH增值法、ISO法）、蛋白溶解度（PS）、考马斯亮蓝值、DBL（可利用赖氨酸）测定，并进行了各个指标的相关性研究。结果表明，各指标均随加热时间的延长和加热温度的升高而逐渐下降，但下降的幅度各不相同，其中蛋白溶解度与加热时间的关系最为显著。且各指标间存在很强的相关，其回归系数都在0．90以上。用定氮法测定的蛋白溶解度和比色法测定的考马斯亮蓝值之间存在很强的相关，其回归方程y＝32．91＋0．9142x，x＝考马斯亮蓝值，y＝蛋白溶解度（r＝0．98）。两者都可鉴别出不同加热程度特别是加热过度的豆粕。DBL值随加热程度的加深而下降，说明加热破坏了赖氨酸，使赖氨酸有效率下降。粒度对蛋白溶解度影响显著，以60～80目为佳。综上所述，蛋白溶解度和考马斯亮蓝值是评价不同加热程度豆粕的最佳指标。在评定过熟程度上，蛋白溶解度比脲酶活性可靠。

Solvent-extracted soybean flakes from Nan Yuan vegetable oil rendering factory were autoclaved for 0, 12, 20 minutes at 108℃ 5ib/inch2 and for 5, 20, 40, 60 min at121℃15 Pa. The samples were evaluated for Urease activity (△pH, ISO)' protein solubility (PS)by Kjeldahl nitrogen methodand by Coomassie dye binding method,DBL values. The results indicated that all the indexes decreased as the heating time was increased, but the decreased ranges of each index was diffetent. There is a high correlation between the indexes(r=0. 98). The regrssion formula for the relation between the protein solubility and Coomassie dye binding was: y= 32. 91 +0. 9142x(x: Coomassie blue G, y: protein solubility). Both index can evaluate the degree of heating, The fact of DBL's decrease together with the increased heating time suggested that lysine effectiveness was decreased due to the damage of protein under heating process. The samples particle sizes affect protein solubility. The best particle size for analysis was 60~80 mesh.