Impact of Lactiplantibacillus plantarum UCLM56 on the bioactive properties of sheep's milk yogurt before and after in vitro digestion and fermentation

Yogurts are recognized for their health benefits attributed to the bacteria they contain. Lactic acid bacteria produce postbiotic compounds, which are soluble bacterial metabolites secreted by living microorganisms during their metabolic activity, or released after their cellular rupture, that confer some physiological direct and indirect benefits to the host. They comprise bioactive compounds such as gamma-aminobutyric acid (GABA) and short-chain fatty acids (SCFAs), with potential antioxidant and antihypertensive effects. Sheep's milk yogurt, due to its higher protein and fat content, is an excellent medium to enhance these bioactive properties. This study investigates the effects of Lactiplantibacillus plantarum UCLM56 inoculated into sheep's milk yogurt on its bioactive and antioxidant properties, also taking storage time into account. The samples were subjected to in vitro digestion and fermentation to simulate the effect of the gastrointestinal tract. GABA, SCFAs, amino acids (ornithine and tryptophan), biogenic amines, SCFAs and antioxidant capacity were analyzed. Yogurt processing with strain UCLM56 enhanced the production of postbiotic compounds and antioxidant capacity, as well as organoleptic characteristics. It also increased the GABA content to 217 mg/kg and extended shelf life by managing microbial growth through increased acidity. Moreover, after in vitro digestion and fermentation, lactic acid levels increased during refrigerated storage for yogurts with strain UCLM56. In addition, the antioxidant capacity obtained after in vitro fermentation was more than 75 % of total antioxidant capacity. This indicates the important role of the gut microbiota in the release of compounds with antioxidant capacity. Therefore, the use of Lactiplantibacillus plantarum UCLM56 has positive effects in yogurts and can be a good option to improve yogurt characteristics and bioactivity.