Redox stability, antioxidant capacity, and biological responses in an iron-fortified synbiotic Spondias dulcis L. beverage

Synbiotic beverages represent a promising functional food system integrating probiotic activity with prebiotic-enhanced functionality in plant-based matrices, supporting sustainable nutrition. This study evaluated the effects of formulation and storage conditions on the physicochemical properties, antioxidant capacity, and concentration-dependent embryotoxic responses of an iron-fortified ambarella ( Spondias dulcis L.) synbiotic beverage. Four formulations were evaluated: prebiotic (F1), probiotic (F2), synbiotic (F3), and iron-fortified synbiotic (F4). The beverages were stored under ambient (25 ± 2 °C) and refrigerated (4 ± 1 °C) conditions for 8 days. Storage time and temperature significantly affected pH and color stability ( p < 0.05), with greater acidification and chromatic changes observed under ambient storage, whereas refrigeration reduced these changes. Synbiotic formulations (F3 and F4) exhibited greater antioxidant capacity than the single-component formulations, with lower ABTS IC₅₀ values (58.28–61.02 ppm) and higher FRAP reducing power (up to 6.98 mg AAE/100 g). Zebrafish ( Danio rerio ) embryo assays demonstrated concentration-dependent embryotoxic responses, with LC₅₀ values ranging from 22.32 to 54.19 µg/mL, while the iron-fortified formulation exhibited greater sensitivity at higher exposure concentrations. These findings demonstrate that formulation and storage conditions influence the physicochemical properties, antioxidant capacity, and concentration-dependent biological responses of Spondias dulcis L.-based synbiotic beverages. Further studies are required to evaluate metabolomic changes, probiotic viability, and comprehensive safety aspects during storage.