Acid whey (AW) is the liquid co-product arising from acid-induced precipitation of casein from skim milk. Further processing of AW is often challenging due to its high mineral content, which can promote aggregation of whey proteins, which contributes to high viscosity of the liquid concentrate during subsequent lactose crystallization and drying steps. This study focuses on mineral precipitation, protein aggregation, and lactose crystallization in liquid AW concentrates (∼55% total solids), and on the microstructure of the final powders from 2 independent industrial-scale trials. These AW concentrates were observed to solidify either during processing or during storage (24 h) of pre-crystallized concentrate. The more rapid solidification in the former was associated with a greater extent of lactose crystallization and a higher ash-to-protein ratio in that concentrate. Confocal laser scanning microscopy analysis indicated the presence of a loose network of protein aggregates (≤10 µm) and lactose crystals (100–300 µm) distributed throughout the solidified AW concentrate. Mineral-based precipitate was also evident, using scanning electron microscopy, at the surface of AW powder particles, indicating the formation of insoluble calcium phosphate during processing. These results provide new information on the composition- and process-dependent physicochemical changes that are useful in designing and optimizing processes for AW.

酸乳清（AW）是由酸诱导的脱脂乳中酪蛋白沉淀而产生的液体副产物。由于其高的矿物质含量，AW的进一步加工通常具有挑战性，它可以促进乳清蛋白的聚集，这有助于在随后的乳糖结晶和干燥步骤中液体浓缩物的高粘度。这项研究的重点是液体AW浓缩物中（总固体含量约55％）的矿物质沉淀，蛋白质聚集和乳糖结晶，以及两次独立工业规模试验中最终粉末的微观结构。观察到这些AW浓缩物在预结晶浓缩物的加工过程中或储存（24 h）期间固化。前者中更快的固化与乳糖浓缩物中更大程度的乳糖结晶和更高的灰分-蛋白质比有关。共聚焦激光扫描显微镜分析表明存在散乱的蛋白质聚集体（≤10µm）和乳糖晶体（100–300 µm）分布在整个凝固的浓缩浓缩液中。矿物基沉淀物也很明显，使用扫描电镜在AW粉末颗粒的表面表明加工过程中形成了不溶性磷酸钙。这些结果提供了有关成分和过程相关的理化变化的新信息，这些信息可用于设计和优化AW的过程。