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

Abstract

Aims: The rising demand for naturally preserved functional beverages has sparked research into indigenous botanicals as preservatives and flavorings. This study evaluated the microbiological 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. The design was a completely randomized experimental design. Juice samples: A (control) (100% pineapple-cucumber), B (95% pineapple-cucumber:5% bitter leaf extract), C (95% pineapple-cucumber:2.5% of mint and bitter leaf extracts, each), and D (95% pineapple-cucumber:5% mint leaf extract) were stored (280C) for 21 days. Place and Duration of Study: Food Science and Technology Laboratory, Chukwuemeka Odumegwu 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 Total titratable acidity [TTA]) were evaluated. Data analysis was performed using a one-way ANOVA; means separated using LSD (p< .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 pilot-scale development.