Abstract:To promote the high-value utilization of oyster resources，this study used oyster glycosaminoglycan（OGAG） as an ingredient to prepare yogurt. The influence of OGAG addition level on yogurt quality was systematically evaluated by examining its physicochemical properties，lactic acid bacteria count，rheological properties，texture，and microstructure. The research demonstrated that OGAG significantly enhanced the proliferation of lactic acid bacteria，leading to increased lactic acid production，elevated acidity，and a corresponding decrease in pH. As the OGAG addition level increased，both the water-holding capacity and textural properties of the yogurt followed a trend of initial improvement，which then declined. Compared with the blank group（OGAG addition level was 0%），OGAG not only enhanced the antioxidant activity of yogurt （with significant enhancement of DPPH/ABTS+free radical scavenging capacity），but also improved its rheological properties.With the amount of OGAG added was 0.015%，the yogurt showed the greatest water -holding capacity（44.42%），sensory quality （90.60） and texture characteristics. A denser and more continuous spatial structure was formed，as observed by scanning electron microscope （SEM），due to the uniform distribution of OGAG particles within the protein matrix under this condition. Furthermore，the secondary structure analysis revealed that the β-sheet content decreased by 4.13%，while the β-turn increased by 3.80%. This suggest that the addition of OGAG weakened the rigid structure of proteins，causing some β-sheets to transform into β-turns，and ultimately forming a more delicate and soft curd structure，which improved the taste and quality of yogurt.