Functional beverages (such as fermented fruit juices and smoothies) have gained popularity among consumers due to their improved nutritional properties and health benefits. This study aimed to determine the metabolic activity of Lactobacillus plantarum and Bifidobacterium bifidum strains and the dynamics of changes in physical parameters (i.e., color, pH, titratable acidity (TA), and total soluble solids (TSS)), viable count, antioxidant activity, and total carotenoid content during the 48-hour fermentation of smoothies consisting of 100% mango and mango mixed with plum (10:1; w/w).

The results showed a significant decrease in the pH of mango and mango--plum smoothies and consequently a significant increase in TA during fermentation with L. plantarum and B. bifidum. However, no significant difference was observed in TSS values during 48-hour fermentation, with values in the range of 7.5-8 °Brix. Counts of both strains decreased after 24 h in mango smoothies, while it continued to increase up to 9.01 log₁₀ (CFU/g) during 48 h of fermentation in mango--plum smoothies. Furthermore, a significant increase in the antioxidant properties (29%) of smoothies was observed after fermentation, which was shown to be higher in mango--plum smoothies than mango ones. Lactic acid fermentation had no significant impact on the total carotenoid content of smoothies. This study demonstrated the potential for lacto-fermented mango-based smoothies to improve functional properties.