Effects of Ultrafiltration Combined with Electric Field on Process Optimization, and Physiochemical Characteristics of Date Juice after Depectinization

Depectinized Date Juice (DDJ) was clarified with an ultrafiltration (UF) unit (containing PVDF-membrane with 30-40 nm pore sizes) and combined with an electric field (EF). The UF had 3 independent variables (temperature, pressure, and flow rate) respectively at [27 & 40oC], [1, 1.5, & 2 bar], and [10, 15, and 20 mL/s] levels. After applying a statistical tool, the optimized levels and affecting factors of temperature, pressure, and flow rate on the resulting permeate sequentially were 40°C & 55.23%, 1.5 bar & 43.01%, and 20mL/s & 1.76%. While the highest permeate flux of UF reached 2.5, it amplified to 5 Kg/m2h (100% increase) when it was joined with the EF at 5 V strength. Although UF permeate could recover 68% and 58% of the phenolic and antocyanin compounds of DDJ, the UF+EF processes improved these recoveries and reached 92% and 80%, respectively. Similarly, the sucrose and glucose in the permeate of UF+EF were at least 10% more than those obtained in the permeate of UF only. The redness color in retentates of DDJ after passing UF and UF+EF concentrated up to 213% and 292%, respectively.  Finally, the application of UF and UF+EF could eliminate the bacterial loads (Enterobacteriaceae, Escherichia coli, mold, and osmophilic yeast) of DDJ below the permissible levels. Overall, the combination of UF+EF could clarify the DDJ with richer bioactive compounds, more reducing sugar, brighter color, and lesser turbidity than those treated with UF only. It also produces a retentate with higher pectin content as a valuable source for making supplementary food.