Formulation and characterization of hybrid milk containing bovine and Spirulina proteins

Abstract

The incorporation of microalgal protein into dairy products presents a sustainable and innovative approach to address rising global protein demands. This study developed model hybrid milk formulations (HMFs) by combining Spirulina protein concentrate (SPC) and milk protein concentrate (MPC), in which SPC replaced 25%, 50%, 75%, and 100% of the total protein content (w/w). A formulation with 100% MPC was used as the control. The fat and mineral contents of the HMFs were standardized using ghee and simulated milk ultrafiltrate (SMUF) respectively. Confocal laser scanning microscopy revealed a uniform distribution of fat globules in all formulations, characterized by small initial globule sizes; however, their size increased significantly after 15 days of storage. Increasing SPC levels led to a significant shift toward a greenish-brown hue. HMFs containing 25–75% SPC exhibited significantly higher creaming than those with either 100% MPC or 100% SPC. Increasing SPC levels led to higher viscosity and reduced thermal stability, with gelation occurring at lower temperatures. This reduction in thermal stability was supported by lower protein denaturation temperatures observed for SPC compared to MPC. Corresponding structural analysis showed a progressive loss of ordered conformation, with decreased β-sheet and increased random coil content, which contributed to the altered gelation behaviour. Among the formulations, the 25% SPC (75% MPC) blend most closely resembled the 100% MPC in terms of color, creaming, viscosity, thermal stability, and structural integrity, making it the optimal HMF developed using SPC and MPC.