Development and characterization of probiotic Ragi-based composite dairy product

This study aimed to develop and optimize a ragi-based probiotic dairy beverage (RPDB) using two probiotic strains, Limosilactobacillus fermentum NCDC143 (LF) and Lacticaseibacillus rhamnosus NCDC347 (LGG). The ragi amount and fermentation duration were optimized through laboratory-scale trials based on sensory characteristics and antioxidant activity. The final optimized product, fermented with either strain, was acceptable to consumers, with average sensory scores above 7 on a 9-point hedonic scale. Proximate and physicochemical analyses were performed. Both fermented beverages (RPDB-LGG & RPDB-LF) showed significantly higher (p < 0.05) 2, 2-diphenyl-1-picryl-hydrazyl (DPPH) inhibition activity (44% & 46%), Total Phenolic Content (359.83 µg GAE/ml & 374.94 µg GAE/ml), and Total Flavonoid Content (14.58 mg QE/ml & 15.36 mg QE/ml) compared to the non-fermented control. Fourier transform infrared spectroscopy (FTIR) analysis characterized the functional groups in the samples. Ultra-high performance liquid chromatography-quadrupole high-resolution accurate mass spectroscopy (UHPLC-Q-Orbitrap-HRAMS)-based metabolomics revealed important biologically active metabolites in the probiotic beverage. Shelf-life analysis showed both beverages maintained recommended viable probiotic counts (at least 6–7 log CFU/ml) for 21 days at 4 °C. Notably, RPDB-LF exhibited better microbiological stability than RPDB-LGG during storage.