Optimization of Biotechnological Vinegar Production from an Algerian Date Variety Using Indigenous Strains and Response Surface Methodology

Vinegar is a traditional fermented food of increasing industrial interest due to its nutritional, sensory, and bioactive properties. This study aimed to develop and optimize a controlled biotechnological process for vinegar production from the Algerian date cultivar Degla Beida, an abundant yet underexploited local resource. Indigenous Saccharomyces cerevisiae strains isolated from date fruits and Acetobacter sp. strains isolated from traditional date vinegar were employed as starter cultures in a two-stage submerged fermentation process, comprising alcoholic fermentation followed by acetic fermentation. Process optimization was carried out using Response Surface Methodology (RSM) based on a Central Composite Design (CCD), evaluating the effects of initial alcoholic degree (4–10% v/v) and yeast extract supplementation (0.2–0.5 g/L). The statistical models showed excellent fitting and predictive reliability (p < 0.0001; R2 = 94.1–99.1%). Under optimal conditions (7% v/v initial alcohol, 0.2 g/L yeast extract, 30 °C, pH 5), the process yielded a maximum acetic acid concentration of 72 g/L after 11 days, with 80% fermentation efficiency and complete ethanol depletion. The optimized vinegar exhibited enhanced bioactive properties, with a total phenolic content of 620 mg GAE/100 mL and a DPPH radical scavenging activity of 78%, significantly higher than those of the unfermented juice. These results demonstrate the suitability of Degla Beida dates for vinegar production and highlight the potential of indigenous microbial resources for the sustainable valorization of local raw materials through controlled fermentation processes.