Impact of Fermentation of Pumpkin Leaves and Melon Varieties with Lactobacillus Strains on Physicochemical Properties, Antioxidant Activity, and Carotenoid Compounds

This study examined the impact of fermentation using Lactiplantibacillus plantarum (L75) and Bifidobacterium longum (BF) on the total soluble solids (TSS), pH, TA, LAB survival, color properties, ascorbic acid content, total phenolic content (TPC), carotenoid components, and antioxidant properties of smoothies made from melon varieties (Cantaloupe, Honeydew, and Watermelon) separately with pumpkin leaves (Cucurbita moschata and Cucurbita pepo). For all smoothies, pH (r = −0.74) and TSS (r = −0.79) were inversely and strongly correlated with LAB counts, while LAB counts were positively correlated with TA (r = 0.87). Fermentation time (24 to 72 h) significantly (p < 0.05) decreased the TSS (%), pH, and color properties of all smoothies fermented with L75 or BF, while TA increased. Fermenting Cantaloupe melon and C pepo leaves with L75 (CMCL75) for 24 h increased the ascorbic acid content to 3.8 mg/100 mL. The sensory panel scores were highest for Watermelon and C. moschata or C. pepo fermented with L75 or BF for 24 h. TPC concentration was highest in CMCL75 (70.76 mg of gallic acid per 100 mL) after 24 h. C. pepo leaves and Cantaloupe fermented with L75 (CPCL75) showed the highest concentration of total carotenoids (70.38 mg/100 mL), lutein (2.53 µg/100 mL), cis β-carotene (25.43 µg/100 mL), and trans β-carotene (620.37 µg/100 mL). In contrast, CMCL75 showed the highest concentration of zeaxanthin (0.70 mg/100 mL). This study demonstrated the potential of fermenting Cantaloupe and pumpkin leaves together with the L75 strain to produce non-dairy functional products.