Development, Characterization, and Stability of Flavored Water Kefir: Impact of Fermentation and Storage

The increasing demand for functional beverages sparked greater interest in craft drinks with these qualities, highlighting the need to optimize production parameters and assess their stability. This study aimed to develop, optimize, and characterize a grape juice-flavored naturally carbonated water kefir, evaluating its sensory qualities, physico-chemical and microbiological stability. Fermentation conditions (F1) were optimized us-ing Central Composite Rotational Design, leading to the selection of 24 hours at 30°C with 6.5% brown sugar, ensuring efficient pH reduction to safe levels. Sensory analysis enabled selecting grape juice as the flavoring agent, and a Mixture Design coupled with the Desir-ability Function determined the optimal formulation as 50% kefired water, 46.4% grape juice, and 3.6% water, resulting in high overall sensory desirability. During 42 days of re-frigerated storage (4°C), the beverage exhibited progressive sugar consumption due to re-sidual metabolic activity, a dynamic antioxidant profile characterized by increases in total phenolic compounds and FRAP activity, stability in ABTS activity, and decline in DPPH activity. Lactic acid bacteria counts remained stable during storage, while acetic acid bac-teria and yeast populations decreased. Furthermore, pH (~3.30) and alcohol content (~1.86 °GL) remained stable, although the latter requires clear labeling in compliance with regu-lations for similar fermented beverages.