Investigating the Physicochemical and Antioxidant Properties of Goat Milk Enriched With Rice Extract Fermented by Exopolysaccharide-Producing Lactic Bacteria for Functional Yogurt Production

Abstract

In recent years, the development of functional dairy products incorporating plant-based ingredients has gained considerable attention due to growing consumer interest in health-promoting foods. In this regard, the present study is aimed at developing probiotic fermented goat's milk using Lactiplantibacillus plantarum (ATCC 1058) and Lacticaseibacillus casei (ATCC 39392) strains. A key focus was on assessing the impact of rice extract (RE) incorporation on the viability and metabolic activity of these probiotic strains. To achieve this, goat's milk samples were inoculated with a probiotic mixture containing both strains at a concentration of 109 log colony-forming units (CFUs)/mL. Various concentrations of RE (0%, 2%, 4%, and 6%) were introduced to the milk samples. The ensuing fermented milk samples were then refrigerated for 28 days, during which assessments were conducted at 7-day intervals. Parameters under investigation included probiotic viability, acidity, pH, acetic acid content, L-lactic acid content, protein content, reducing sugar levels, Brix degree, viscosity, antioxidant potency, color attributes (brightness, yellowness, and redness), and sensory attributes. The study revealed significant changes in the physicochemical traits of the fermented milk during storage. Notably, acidity, L-lactic acid, acetic acid, and viscosity increased, while pH, reducing sugars, Brix, antioxidant strength, and probiotic levels decreased (p ≤ 0.05). The addition of RE and its increasing concentration intensified these shifts. Importantly, this effect corresponded with improved antioxidant activity and probiotic viability (p ≤ 0.05). The sample with 6% RE displayed the highest antioxidant potency (55.46%) and probiotic count (9.21 log CFU/mL) at the study's end, followed by the 4% RE sample. Furthermore, sensory assessment revealed that the 6% RE sample had the lowest acceptability score, whereas the other samples were well-received. Ultimately, with the provided outcomes, the optimal treatment for producing probiotic fermented milk with desirable functional attributes was determined to be a 4% concentration level of RE.

Keywords: antioxidant activity; fermented milk; goat milk; probiotics; rice extract.