Impact of storage conditions on solubility, heat stability and emulsifying properties of selected spray dried whey protein concentrates

Storage conditions and composition of whey protein concentrates (WPCs) may destabilize the whey proteins (WPs) thus affect their functionality. Functional characteristics of native, sweet, acid and salty-WPC powders were analyzed after storage at 25 °C and RH (22, 33%) for 90 days. Native-, sweet- and acid-WPCs exhibited high solubility (82-97%), which was largely retained during storage. Solubility of salty-WPC was 52-55% initially, which gradually increased by ∼5% during storage. Ionic sodium in salty-WPC interlinked WPs through salt bridges and charge screening, exposing reactive sites for intensive aggregation. Heat stability of salty-WPC was highest (64s), while lowest was recorded for native-WPC (16s). In presence of ionic sodium in salty-WPC, WPs denature due to salt bridging, charge screening and osmotic effects leading to intensive aggregation. High emulsion activity was recorded for salty-WPC, while those for other WPCs were similar. Emulsion stability varied as native- > acid- > salty- > sweet-WPC. High number of hydrophobic segments was likely exposed on the protein surface in salty-WPCs due to sodium-induced WP denaturation, thus increasing the number of proteins absorbed to emulsion interface, enhancing emulsion activity. Functionality of different WPCs during storage predominantly depended on the inherited composition.