Department of Food Science, The University of Tennessee, Knoxville 37996.
Department of Food Science, The University of Tennessee, Knoxville 37996.
J Dairy Sci. 2020 Nov;103(11):9868-9880. doi: 10.3168/jds.2020-18644. Epub 2020 Aug 26.
Due to health benefits of proteins, the demand for protein beverages has grown rapidly. Translucent protein drinks with neutral pH may have advantages over acidic beverages that may cause dental erosion, and skim milk powder (SMP) is an affordable protein ingredient. Dissociating casein micelles by calcium chelators is a well-known method to reduce SMP dispersion turbidity, but much is to be studied for physicochemical properties as affected by chelator type and concentration. The objective of the present study was to characterize physicochemical properties of dispersions with 5% (wt/vol) SMP after addition of 0 to 30 mM sodium tripolyphosphate, trisodium citrate, or sodium hexametaphosphate. The turbidity was decreased with increasing chelator concentration, with the lowest turbidity observed in the SMP dispersions with sodium hexametaphosphate. The smallest hydrodynamic diameter was observed at an intermediate chelator concentration, resulting from the balance of casein micelle dissociation and aggregation of dissociated caseins induced at an elevated ionic strength. Heating at 90°C for 5 min increased turbidity but lowered hydrodynamic diameter of SMP dispersions, with some exceptions. The morphology of SMP dispersions differed for each chelator and was also affected by chelator concentration and heating. Trisodium citrate was the most effective to demineralize colloidal calcium phosphate in casein micelles, but the amount of dissolved calcium was not directly correlated with the decreased turbidity, indicating different chelating mechanisms by each chelator. Analysis of serum calcium and phosphorus concentrations also suggested that the type and concentration of soluble and insoluble calcium phosphates and their partitioning in the serum and casein micelles were dynamically changed by the studied parameters to affect dispersion turbidity and structures of casein micelles. Findings from the present study may be used to formulate translucent beverages incorporating SMP and other casein micelle ingredients.
由于蛋白质对健康有益，因此对蛋白质饮料的需求迅速增长。具有中性 pH 值的半透明蛋白饮料可能比酸性饮料具有优势，因为酸性饮料可能会导致牙齿侵蚀，而脱脂奶粉 (SMP) 是一种经济实惠的蛋白质成分。通过钙螯合剂使酪蛋白胶束解离是降低 SMP 分散体系浊度的常用方法，但螯合剂类型和浓度对其理化性质的影响还有很多需要研究。本研究的目的是研究添加 0 至 30 mM 三聚磷酸钠、柠檬酸钠或六偏磷酸钠后，5%（wt/vol）SMP 分散体系的理化性质。随着螯合剂浓度的增加，浊度降低，而添加六偏磷酸钠的 SMP 分散体系的浊度最低。在中间的螯合剂浓度下，观察到最小的水动力直径，这是由于在提高的离子强度下诱导的酪蛋白胶束解离和解离的酪蛋白聚集之间的平衡所致。在 90°C 下加热 5 分钟会增加 SMP 分散体系的浊度，但降低其水动力直径，但有些例外。SMP 分散体系的形态因螯合剂而异，也受螯合剂浓度和加热的影响。柠檬酸钠对去除酪蛋白胶束中的胶体磷酸钙最有效，但溶解钙的量与浊度降低不成直接相关，表明每种螯合剂的螯合机制不同。血清钙和磷浓度的分析也表明，研究参数动态改变了可溶性和不溶性磷酸钙的类型和浓度及其在血清和酪蛋白胶束中的分配，从而影响分散体系的浊度和酪蛋白胶束的结构。本研究的结果可用于配制含有 SMP 和其他酪蛋白胶束成分的半透明饮料。
