Enhancement of rheological, textural, and sensory properties in full-fat stirred yogurt through protein-glutaminase deamidation

The rheological, textural, and sensory properties of yogurt are crucial for its consumer acceptance. This study investigated the effects of protein glutaminase (PG) -induced deamidation on these properties of full-fat stirred yogurt. At a PG concentration of 0.3 U·mL⁻¹, the deamidation degree of milk proteins reached its peak at 59.50 %, resulting in improved solubility, reduced turbidity, and an increased proportion of smaller particles. Additionally, PG treatment enhanced yogurt acidity and water-holding capacity. Low-field nuclear magnetic resonance analysis revealed stronger hydrogen proton binding in yogurt, indicating stronger binding of proteins to water due to PG-induced deamidation. Confocal laser scanning microscopy showed a gradual reduction in the protein particle size with increasing PG concentration. Rheological and textural analyses indicated that PG deamidation dissociated the protein micelle structure, resulting in a smoother and creamier texture and improved sensory characteristics. These findings provide practical insights for optimizing the quality of full-fat stirred yogurt for diverse food and industrial applications.