The production of citric acid from dates of the date palm Phoenix dactilifera was studied using a full factorial design with two design variables; Aspergillus niger strain, and starter juice treatment. Analyses of data have shown that mould type and the interaction between Aspergillus niger strain + juice treatment had significant effect (P ≥ 0.05) on the final total acidity. It was also found that all design variables and the interaction between them had significant effect (P ≥ 0.05) on the final pH and Total Soluble Solids. The highest total acidity expressed as citric acid was achieved with a commercial strain of Aspergillus niger, and filtered and centrifuged date juice.
 Al-Farsi, M., Alasalvar, C., et al. (2007) Compositional and Functional Characteristics of Dates, Syrups, and Their By-Products. Food Chemistry, 104, 943-947. http://dx.doi.org/10.1016/j.foodchem.2006.12.051
 Lotfy, W.A., Ghanem, K.M., et al. (2007) Citric Acid Production by a Novel Aspergillus niger Isolate: II. Optimization of Process Parameters through Statistical Experimental Designs. Bioresource Technology, 98, 3470-3477.