Characterization of Composite Protein Powder from Milk and Sorghum Protein Processed with Heat and Salt Treatment

Abstract This study aimed to develop and characterize milk-sorghum composite protein powders prepared using heat- and salt-induced protein interactions. Composite protein systems were formulated by blending sorghum protein concentrate (SPC) with skim milk in a 1:1 protein ratio. Heat treatment (90 °C/30 min) and salt addition (1% sodium metabisulfite) were used to induce protein interactions prior to ultrafiltration and spray drying. This method was used for the development of heat-treated composite protein powder (HCPP) and salt-treated composite protein powder (SCPP). Milk protein concentrate (MPC) and SPC were used as control samples. Physical analysis showed that HCPP and SCPP had lower occluded and interstitial air contents than MPC, improving density and reducing porosity. SCPP exhibited significantly enhanced solubility (78.56%) and superior emulsifying stability, while HCPP demonstrated improved functional properties due to heat-induced unfolding. SEM analysis revealed smoother surfaces and smaller particle clusters in composite powders than in SPC, indicating stronger protein-protein interactions and highlighting their potential as value-added ingredients for food applications.