Physical properties of selected spray dried whey protein concentrate powders during storage

Storage conditions may compromise stability of whey proteins in dry state, which is also influenced by their inherent composition. Thus, physical characteristics of native, sweet, acid and salty-WPC powders were analysed during storage at several temperatures (4, 25, 45 °C) and relative humidities (22, 33%) for a period of 90 days. Particle surface of native, sweet and acid-WPCs was dominated by proteins under all storage conditions, while fat and minerals prevailed on the surface of salty-WPC. Compared to native- and sweet-WPCs, origin of acid- and salty-WPCs influenced these streams to be rich in minerals, primarily accumulated in the particle core. Hydrophilic nature of the core impacted redistribution of proteins within the particle during storage. Compared to native- and sweet-WPC, particles were cohesively arranged in acid- and salty-WPC, which in turn changed physical properties such as particle size and surface charge. Elevated storage temperatures induced protein denaturation, melting of surface free fat and lactose crystallization in WPCs, while humidity regulated the molecular mobility in these reactions.