Evaluation of the Bacterial Inhibitory Activity of Rhodotorula mucilaginosa on the Sensory Qualities of the Juice Compared with the Synthetic Dye

Abstract

This study aimed to evaluate the inhibitory activity of the microbial dye extracted from the yeast Rhodotorula mucilaginosa, isolated from local oleander flowers. Beta-carotene dye was extracted and identified using high performance liquid chromatography (HPLC) technique. The results showed that the microbial dye exhibited inhibitory activity against Escherichia coli, Staphylococcus aureus, and Salmonella. A concentration of (0.1 g/ml) showed no inhibitory effect. At (0.2 g/ml), inhibition was observed only against Staphylococcus aureus with a diameter of (10.00 mm). Concentrations of (0.3, 0.4, and 0.5 g/ml) showed inhibition against all tested bacteria, with inhibition zones at (0.3 g/ml) being (5.00, 12.00, and 5.00 mm), at (0.4 g/ml) being (10.00, 15.00, and 8.00 mm), and at (0.5 g/ml) reaching the highest values of (12.00, 15.00, and 10.00 mm), respectively. Sensory evaluation of juice containing the microbial dye compared to synthetic dye showed a significant improvement in color (9.96 vs. 7.96, p < 0.05), with no significant differences in taste and flavor. A significant enhancement (p < 0.05) was noted in the texture (9.6 vs. 7.86) and overall acceptability (9.74 vs. 7.19) of the microbial dye. The findings demonstrate that the microbial dye not only possesses antimicrobial properties that help extend the shelf life of foods and beverages but is also well accepted by consumers. Additionally, it serves as a source of vitamin A and plays a valuable biological role in human health.