Universidad Autónoma de Chihuahua, Facultad de Ciencias Químicas, Departamento de Posgrado, Chihuahua, Mexico.
Universidad Autónoma de Chihuahua, Facultad de Ciencias Químicas, Departamento de Posgrado, Chihuahua, Mexico.
Food Res Int. 2019 Feb;116:455-461. doi: 10.1016/j.foodres.2018.08.061. Epub 2018 Aug 22.
Lactose is recovered by crystallization from cheese whey that is a by-product of cheesemaking. The whey used for the recovery of lactose usually has a residual content of protein that alters the crystallization of lactose. In addition, the pH of whey may fluctuate depending on the cheese variety. However, there is little information on how the pH modifies the effect that whey proteins have on lactose crystallization. Accordingly, this work aimed to evaluate the individual and combined effect of whey proteins and pH on the kinetics of crystallization, the crystal size distribution and the crystallinity of lactose. The addition of whey proteins in lactose solutions (25% v/v) modified the process of lactose crystallization. However, the effect that whey proteins had on lactose crystallization heavily depended on the pH. The number of crystals per milliliter as well as the growth and size distribution of crystals was the most affected with the changes in pH (pHs of 7, 5.5 and 4) and the addition of whey proteins (0 and 0.63%). All the treatment produced mostly α-lactose monohydrated but some treatments also generated crystals of β-lactose (pH 5.5, 0% of proteins). Amorphous lactose was observed mainly in lactose solutions adjusted at pH 7 and added with whey proteins. This particular treatment also incorporated the highest amount of protein into the lattice of lactose crystals. The results of this work highlight the importance of controlling the pH of lactose crystallization, especially if there is a presence of whey proteins.
乳糖是从奶酪乳清中结晶回收得到的，而乳清是奶酪生产的副产品。用于回收乳糖的乳清通常含有残留的蛋白质，这些蛋白质会改变乳糖的结晶。此外，乳清的 pH 值可能会根据奶酪的种类而波动。然而，关于 pH 值如何改变乳清蛋白对乳糖结晶的影响的信息却很少。因此，本工作旨在评估乳清蛋白和 pH 值对乳糖结晶动力学、晶体粒度分布和乳糖结晶度的单独和联合影响。乳清蛋白的添加会改变乳糖溶液（25% v/v）的结晶过程。然而，乳清蛋白对乳糖结晶的影响在很大程度上取决于 pH 值。随着 pH 值（7、5.5 和 4）和乳清蛋白添加量（0 和 0.63%）的变化，每毫升晶体数以及晶体的生长和粒度分布受到的影响最大。所有处理均主要产生一水合α-乳糖，但某些处理也会生成β-乳糖晶体（pH 5.5，无蛋白质）。无定形乳糖主要在 pH 值为 7 并添加乳清蛋白的乳糖溶液中观察到。这种特殊处理还将最多量的蛋白质纳入了乳糖晶体的晶格中。本工作的结果强调了控制乳糖结晶 pH 值的重要性，特别是在存在乳清蛋白的情况下。
