Physicochemical properties, microstructure and protein profiling of camel milk powder: A comparison of spray drying...

Camel milk has gained increasing research interest as a high-value dairy product due to its unique nutritional composition and potential health benefits. However, the impact of low-temperature vacuum drying (LVD) on the quality and nutritional properties of camel milk powder remains largely unknown. This study systematically compared the physicochemical properties, microstructure, and protein profiles of camel milk powders produced by spray drying and LVD. The LVD-produced milk powder exhibited significantly higher moisture content, solubility, b* value, and particle size compared to spray-dried powder. Microstructural analysis revealed that spray-dried milk powder existed as aggregates of spherical particles, whereas LVD-produced powder displayed irregular and fragmented structures. Compared with raw camel milk, the α-helix content of spray-dried and LVD-produced milk powders decreased to 15.38 % and 15.72 %, respectively, while the random coil content increased to 16.54 % and 16.17 %. A total of 192 differentially expressed whey proteins (113 upregulated and 79 downregulated) were identified in the LVD-produced milk powder relative to spray-dried powder. Notably, LVD better preserved highly abundant whey proteins, including lactoferrin, lactoperoxidase, xanthine dehydrogenase/oxidase, α2-macroglobulin, lactadherin, amine oxidase, and Ig mu chain C region. Gene Ontology analysis indicated that these differentially expressed proteins were primarily associated with immune-related functions and insulin receptor signaling pathway. KEGG enrichment further revealed their involvement in N-glycan biosynthesis and IL-17 signaling pathway. Furthermore, ELISA confirmed that LVD-produced milk powder contained significantly higher levels of lactoferrin and lactoperoxidase. Collectively, these results establish a theoretical framework for optimizing processing protocols to produce high-quality camel milk powder.