Does ultrafiltration have a lasting effect on the physico-chemical properties of the casein micelles?

The objective of this work was to determine if concentration of milk using ultrafiltration (in the absence of diafiltration) affects the physico-chemical properties of the casein micelles. The milk, once concentrated, was brought back to its original concentration and the physico-chemical properties as well as its susceptibility to rennet induced gelation were assessed. Although much is understood on the renneting behavior of concentrated milk, no information is available on how (or if) ultrafiltration per se modifies the properties of the micelles. Two times (2×) or five times (5×) concentrated milk (based on volume reduction) was prepared by ultrafiltration. Casein micelles were redispersed in their corresponding permeates and dialyzed against untreated skim milk. The stability of the casein micelles, their scattering properties, and the renneting properties were observed under the same volume fraction and ionic conditions of the skim milk control. There was a higher susceptibility to aggregation and a lower gel stiffness for the reconstituted micelles from the 5× milk compared to the 2× milk. 5× Ultrafiltration induced losses of calcium from the micelle, while 2× milk showed similar value as the control. The results suggest that the process of ultrafiltration affected the internal structure of the Dairy Sci. & Technol. (2011) 91:151–170 DOI 10.1007/s13594-011-0002-0 M. A. Ferrer University of Zulia, Maracaibo, Venezuela e-mail: [email protected] M. A. Ferrer :M. Alexander :M. Corredig (*) Department of Food Science, University of Guelph, Guelph N1G 2W1 ON, Canada e-mail: [email protected] M. Alexander e-mail: [email protected] casein micelles, and this caused changes in the light-scattering properties and renneting functionality. 超滤是否对酪蛋白胶束的物理化学特性产生持续性的影响? 摘要 本文的目的是确定超滤 (未经过二次超滤) 是否对酪蛋白胶束的物理化学 性质产生影响。将浓缩后的牛奶还原到原奶的浓度, 然后评价了乳对凝乳酶的 敏感性等物理化学性质。尽管对浓缩乳的凝乳特性已经有了深入的了解, 但是 对超滤是否对酪蛋白胶束性质产生影响, 有关这方面的研究信息非常有限。制 备2倍或5倍的超滤浓缩乳, 然后将浓缩乳重新分散到相应的透过液中并在未处 理的脱脂奶中透析。以脱脂乳作对照组,测定了酪蛋白胶束稳定性,酪蛋白胶束 的光散射特性及其凝乳特性。与2倍超滤浓缩物的还原奶相比, 5倍超滤浓缩物 的还原奶中酪蛋白胶束凝聚敏感性较高但形成凝胶的硬度较低。5倍超滤浓缩 过程导致了胶束中钙的丢失,而2倍的超滤浓缩乳与对照组相似的性质。研究结 果表明超滤过程影响了酪蛋白胶束的内部结构, 进而影响了光散射和凝乳特性