Optimization of Traditional Date Vinegar Preparation Using Full Factorial Design

In the Algerian Sahara, traditional date vinegar (TDV) is still homemade and consumed at family scale. For this, the spontaneous alcoholic and acetic fermentations are conducted simultaneously in one step. In the present study, an attempt was made to improve this traditional procedure at laboratory scale, using full factorial design. Three dependent variables, namely, total soluble solids (degrees Brix), total acidity (TA), and residual alcohol (RA) of obtained TDV sample were considered, the independent variables (factors) being the perforation diameter (D) of the container lid and the ratio of container headspace height (H) to liquid-air interface area (S). The results showed that first-order polynomial equations (F value > 13, R-2 > 0.80, and adjusted R-2 > 0.74) describe correctly the relationship between responses and factors. The three-dimensional surface plots indicated that the TA value increased with D increasing and H/S decreasing, with the maximal value reached being about 6% (w/v) acetic acid. In addition, the GC-MS analysis of distillate from elaborated TDV with the highest TA revealed that acetic acid was predominant, accounting for about 81% of total volatiles. FT-IR and antibacterial activity of the TDV were also carried out.