Evaluation of the survival of homofermentative Lacticaseibacillus casei subsp. casei in fermented milk matrix enriched with non-digestible natural fibers

The physicochemical changes induced by seven different dietary fibers (oat, bamboo, pea, inulin, apple, potato, and wheat) during storage and their effects on the survival of homofermentative Lacticaseibacillus casei subsp. casei (L. casei) in fermented milk matrix were analyzed. For this, an experimental study of the effect of storage time on the microorganisms count and physicochemical properties (pH, titratable acidity, syneresis and viscosity) of milk fermented with L. casei was carried out every two weeks during a storage period of 42 days. Throughout the period studied at 4 °C, no significant differences were found in terms of viscosity values, syneresis rates and L. casei counts, despite the substantial decrease in the pH values. Notably, the substantial increase in the concentration of free hydronium ions (active acidity) in the fiber-enriched matrices during the follow-up period was positively correlated with the L.casei survival. The microbial count determined in all samples was higher than 1 × 10⁷ CFU/g, the minimum value recommended by world organizations for nutraceutical fermented foods. Consequently, the studied prebiotic fibers could be considered in the production of new fermented dairy products with functional properties. Graphical abstract: [Figure not available: see fulltext.]