Variations in quality attributes of cow and goat milk subjected to microwave and high-pressure treatments over a two-week storage period

Abstract

This study investigates the effects of heat, microwave (MW), and high-pressure (HP) treatments on microbial inactivation, physicochemical properties, and storage changes in cow and goat milk to clarify processing-induced differences. MW (1000 W, 45 s) and HP (500 MPa, 5–10 min) significantly reduced microbial counts and eliminated coagulase-positive Staphylococci, indicating improved microbial quality. HP treatment further decreased brightness (L*) in both milk types, and L* declined significantly across all treatment groups during the 14 d storage period, suggesting altered visual quality. HP treatment also enlarged casein micelle and fat globule size, while storage resulted in a reduction of micelle size and an increase in fat globule size in cow milk. MW treatment notably increased α-helix content in goat milk proteins, whereas HP treatment reduced α-helix structures while increasing β-sheet and random coil conformations in both milk types. During storage, both MW and HP treatments exhibited further reductions in α-helix content and increases in disordered structures, although HP-treated samples maintained greater structural stability. MW and HP also enhanced milk protein fluorescence intensity and surface hydrophobicity, both of which declined progressively during storage, likely due to aggregation and conformational changes. These results support MW and HP as viable non-thermal pasteurization technologies that enhance microbial safety and influence structural attributes of dairy proteins. Further optimization is needed to improve product stability and shelf life, with process conditions customized to specific milk types for industrial application.