In Vitro Gastrointestinal Stability and Functional Evaluation of Yogurt Fortified With Paraprobiotics and Postbiotics

In this study, yogurt formulations with paraprobiotic (heat inactivated Lactobacillus acidophilus) and postbiotic (autolyzed and dried Saccharomyces cerevisiae) additions were developed to improve the techno-functional properties of yogurt/probiotic yogurts. Yogurt/probiotic yogurt samples were prepared by adding 0.5% autolyzed and dried S. cerevisiae and 10⁹ cfu/mL heat-killed L. acidophilus cells and stored at 4°C ± 1°C for 21 days. Using a standard in vitro gastrointestinal digestion model simulating digestion in the gastric and intestinal phases, bacterial survival, antioxidant and phenolic compounds, and antimicrobial properties in yogurt samples were determined and compared with the pre-digestion. The addition of inactive L. acidophilus cells had no significant effect on the physicochemical, microbiological, antioxidant or antimicrobial properties of yogurt samples. In contrast, the physical, chemical, and sensory properties of the samples containing autolyzed and dried S. cerevisiae were affected, and these effects also varied with storage time. The antioxidant and phenolic contents of the samples increased by 69%-117% and 8%-25%, respectively, during the gastric digestion compared to pre-digestion levels, whereas after intestinal digestion, these values reached 122%-208% and 135%-172%. In vitro digestion analyses revealed that samples containing postbiotics and paraprobiotics exhibited higher levels of bioavailable compounds throughout the digestion stages. These findings suggest that the addition of postbiotics and paraprobiotics may be an effective strategy to improve the functional properties of fermented dairy products.