Heat stability of high-protein calcium-fortified milk protein concentrate dispersions: Impact of different calcium salts.

Calcium fortification remains a challenge for high-protein beverages. The current study investigated the impact of different calcium fortification, i.e., calcium chloride (CaCl₂), calcium gluconate (CaGlu), and chelated calcium casein pHosphopeptide (CaCPP) on the physicochemical properties and heat stability of high-protein (8.0 % protein) milk protein concentrate (MPC) dispersions. MPC suspensions were fortified with 2.5-15 mM calcium in the form of CaCl2, CaGlu and CaCPP then analyzed for pH, zeta potential, calcium ion activity, heat coagulation time (HCT), sedimentation ratio, ethanol stability, particle size distribution, and sediment and protein distribution after heat treatment. The results showed that CaCl₂ and CaGlu fortification significantly (p < 0.05) decreased the heat and ethanol stability of MPC dispersions, leading to rapid protein aggregation and micelle destabilization due to high calcium ion activity. In contrast, CaCPP fortification demonstrated remarkably superior stability than CaCl2 and CaGlu fortification under thermal stress. At a calcium concentration of 2.5 mM, the HCT value decreased from 18.36 min in the control group to 0.71 min with CaCl₂ and 0.85 min with CaGlu, indicating severe destabilization. However, CaCPP maintained a significantly higher HCT of 9.36 min, which is attributed to its ability to reduce free calcium ion activity and preserve the structural integrity of casein micelles. SDS-PAGE and RP-HPLC confirmed that CaCPP preserved higher soluble casein levels compared to CaCl₂ and CaGlu treatments. These findings indicated that CaCPP is a promising calcium fortifier for producing heat-stable, calcium-enriched high-protein beverages, which showed great feasibility in dairy and sport beverage industry.