Kuipers Bas J H, van Koningsveld Gerrit A, Alting Arno C, Driehuis Frank, Gruppen Harry, Voragen Alphons G J
Centre for Protein Technology, Wageningen, The Netherlands.
J Agric Food Chem. 2005 Feb 23;53(4):1031-8. doi: 10.1021/jf048622h.
Acid-induced cold gelation of soy protein hydrolysates was studied. Hydrolysates with degrees of hydrolysis (DH) of up to 10% were prepared by using subtilisin Carlsberg. The enzyme was inhibited to uncouple the hydrolysis from the subsequent gelation; the latter was induced by the addition of glucono-delta-lactone. Visual observations, confocal scanning laser microscopy images, and the elasticity modulus showed that hydrolysates gelled at higher pH values with increasing DH. The nonhydrolyzed soy protein isolate gelled at pH approximately 6.0, whereas a DH = 5% hydrolysate gelled at pH approximately 7.6. Gels made from hydrolysates had a softer texture when manually disrupted and showed syneresis below a pH of 5-5.5. Monitoring of gelation by measuring the development of the storage modulus could be replaced by measuring the pH onset of aggregate formation (pH(Aggr-onset)) using turbidity measurements. The rate of acidification was observed to also influence this pH(Aggr-onset). Changes in ionic strength (0.03, 0.2, and 0.5 M) had only a minor influence on the pH(Aggr-onset), indicating that the aggregation is not simply a balance between repulsive electrostatic and attractive hydrophobic interactions, but is much more complex.
研究了酸诱导大豆蛋白水解物的冷胶凝作用。使用枯草杆菌蛋白酶卡尔伯格制备水解度（DH）高达10%的水解物。抑制该酶以使水解与随后的胶凝作用解偶联；后者通过添加葡萄糖酸 - δ - 内酯诱导。视觉观察、共聚焦扫描激光显微镜图像和弹性模量表明，随着DH增加，水解物在更高的pH值下发生胶凝。未水解的大豆分离蛋白在pH约为6.0时胶凝，而DH = 5%的水解物在pH约为7.6时胶凝。由水解物制成的凝胶在手动破坏时质地更软，并且在pH低于5 - 5.5时出现脱水收缩。通过测量储能模量的发展来监测胶凝作用，可以用使用浊度测量来测量聚集体形成的起始pH（pH(Aggr-onset)）来替代。观察到酸化速率也会影响这个pH(Aggr-onset)。离子强度（0.03、0.2和0.5 M）的变化对pH(Aggr-onset)只有轻微影响，这表明聚集不仅仅是排斥性静电相互作用和吸引性疏水相互作用之间的平衡，而是要复杂得多。
