Abstract: [Objective] This study aimed to evaluate the dynamic effects of direct and indirect sterilization processes on the content and composition of free monosaccharides in bovine milk,addressing the current research gap in comparing these two heating methods.[Method] The contents of arabinose,galactose,mannose,ribose,xylose,glucose,and fucose were quantitatively analyzed using liquid chromatography-mass spectrometry （LC-MS）. Statistical evaluation was performed via one-way ANOVA,Tukey's post-hoc test,principal component analysis （PCA）,and hierarchical clustering for multivariate analysis.[Result] Heat treatment significantly altered the monosaccharide profile：the contents of galactose,mannose,ribose,and fucose decreased in a dose-dependent manner with increasing temperature （all p<0.01）. Glucose content increased significantly by 75.0% [（37 182.40±1 063.18）ng/mL] at 75 ℃ but decreased by approximately 8.2% and 7.3% at 122 ℃ and 130 ℃,respectively. Hierarchical clustering analysis further confirmed the dominant role of temperature in regulating monosaccharides,showing higher similarity between the 130 ℃ and 75 ℃ groups,while the 122 ℃ group was distinctly separated. This indicates that short-time high-temperature treatment can inhibit the accumulation of early Maillard reaction products and reduce excessive degradation of heat-sensitive monosaccharides.[Conclusion] This study was the first to reveal the effects of direct and indirect sterilization processes on the free monosaccharide content in raw bovine milk. It provided new experimental data for understanding the mechanisms of lactose degradation and monosaccharide transformation during thermal processing and offers a scientific basis for optimizing dairy processing technologies.

Key words: raw bovine milk, direct sterilization process, indirect sterilization process, free monosaccharides, liquid chromatography-mass spectrometry （LC-MS）