A longitudinal assessment of quality stability and edible safety of commercial yogurt beyond the stated expiration date

This study longitudinally assessed the quality stability and edible safety of two commercial yogurt brands stored at 4 °C, 24 °C, and 32 °C for up to 49 days beyond the expiration date. Microbiological, physicochemical, and sensory analyses were conducted to evaluate changes in safety, functionality, and acceptability. Results indicated that both yogurts remained microbiologically safe, with no detection of Enterobacteriaceae, Salmonella , or Staphylococcus aureus , and yeast/mold counts within regulatory limits (≤ 30 CFU/mL). Lactic acid bacteria count consistently exceeded 1×106 CFU/mL. Both products maintained acceptable quality for 2–3 weeks at 4 °C, with sample B demonstrating superior stability in acidity (fluctuating within only 3.8 °T), viscosity (retaining 2680 mPa·s after 49 days), water-holding capacity (maintaining 59.6–72.6%), and sensory attributes (overall score >80 points at 21 days post-expiration). Elevated temperatures accelerated deterioration, particularly in taste, texture, and structural integrity. sample B, containing Bifidobacterium animalis subsp. lactis and higher protein content, exhibited enhanced resistance to post-expiration quality loss. The findings suggest that yogurt stored at 4 °C may remain edible beyond the labeled date, providing a scientific basis for the dairy industry to consider extending “best-before” periods for certain products and for policymakers to promote the use of differentiated date labels to reduce household food waste.