Department of Food Science, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
J Dairy Sci. 2010 Feb;93(2):506-14. doi: 10.3168/jds.2009-2629.
Nonionic emulsifiers of small molecular weight such as polysorbates are widely used in dairy products. Nevertheless, the mechanism of interaction between these surfactants and milk proteins is not yet fully understood. This work investigated the effect of Tween 20 on casein micelles by studying the renneting behavior of skim milk in the presence of different amounts of surfactant. The presence of Tween accelerated both the first and second phase of renneting in skim milk. The gel obtained showed a higher elastic modulus than that of a skim milk gel, but also showed similar brittleness. By varying the size of the surfactant (Tween 20 or Tween 80) as well as the colloidal state of the proteins in solution, it was possible to demonstrate that the surfactant did not have a direct effect on the activity of the enzyme, but rather had a direct effect on the casein micelles. The effect of surfactant on the gelation point was reduced by increasing surfactant size. The presence of Tween caused an increase in the size of the micelles without affecting their stability. In addition, Tween did not alter the amount of caseins free in the serum phase. These findings can contribute to improving our ability to custom design final structures in rennet-induced gels, though further studies are needed to fully understand the mechanism at play when casein micelles are enzymatically cleaved in the presence of nonionic surfactants of small molecular weight.
非离子型小分子乳化剂如聚山梨醇酯广泛应用于乳制品中。然而，这些表面活性剂与乳蛋白之间的相互作用机制尚不完全清楚。本研究通过研究不同浓度表面活性剂存在下脱脂乳的凝乳特性，考察了吐温 20 对酪蛋白胶束的影响。吐温的存在加速了脱脂乳的凝乳第一和第二阶段。与脱脂乳凝胶相比，所得凝胶的弹性模量更高，但脆性也相似。通过改变表面活性剂（吐温 20 或吐温 80）的大小以及溶液中蛋白质的胶体状态，可以证明表面活性剂对酶的活性没有直接影响，而是对酪蛋白胶束有直接影响。随着表面活性剂尺寸的增加，表面活性剂对胶凝点的影响减小。吐温的存在会增加胶束的大小而不影响其稳定性。此外，吐温不会改变血清相中游离酪蛋白的量。这些发现有助于提高我们在凝乳诱导凝胶中定制最终结构的能力，尽管需要进一步研究才能充分了解在存在小分子非离子表面活性剂时酶促切割酪蛋白胶束时的作用机制。
