Microbial Safety, Antioxidant Capacity, and Physicochemical Changes in Pasteurized Mint- and Vernonia amygdalina-Flavored Pineapple–Cucumber Juice Blend Stored at Ambient Temperature

Aims: The rising demand for naturally preserved functional beverages has sparked research into indigenous botanicals as preservatives and flavorings. This study evaluated the microbial safety, antioxidant capacity, and physicochemical stability of four formulations of pasteurized pineapple-juice blends that contained mint (Mentha spp) and bitter leaf (Vernonia amygdalina Del.) extracts. Study Design: This research is presented as an original article. Methodology: Juice samples A (control) with 100% pineapple–cucumber, B (95% pineapple–cucumber + 5% bitter leaf extracts), C (95% pineapple–cucumber + 2.5% mint and bitter leaf extracts, each), and D (95% pineapple–cucumber + 2.5% mint leaf extracts) were stored (28 ± 2°C) for 21 days. Place and Duration of Study: Food Science and Technology Laboratory, Chukwuemeka Odumegwu Ojukwu University, Anambra State, Nigeria. Juice formulation, storage, and analysis were completed within 21 days in June, 2025. Methodology: Microbiological (total plate count [TPC], total yeast count [TYC], total coliform count [TCC], and total bacterial count [TBC]); antioxidant capacity [DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (Ferric Reducing Antioxidant Power)], and physicochemical parameters (pH and Titratable acidity [TTA]) were evaluated. Data analysis was performed using a one-way ANOVA; means separated using LSD (p < 0.05). Results: All formulations satisfied post-pasteurization standards with TPC below 50 CFU/ml on day 0. By day 21, sample B recorded the lowest microbial counts (TPC, TYC, and TCC = 250, 220, and 220, respectively), while the control recorded the highest. TCC exceeded the mandatory zero-coliform Nigeria’s NAFDAC (National Agency for Food and Drug Administration and Control) standard in all formulations beyond day 7. DPPH and FRAP activity were higher in all composite formulations on day 1, with sample B as the highest. pH decreased, and TTA declined progressively across all samples during storage. Sample B recorded the sharpest TTA reduction (1.05% to 0.25%), while the control was most stable (1.06 to 0.72%). Conclusion: Sample B showed the most favorable and optimal profile for post-scale development.