Response Surface Methodology (RSM) Optimization of Pulsed Electric Field (PEF) Pasteurization Process of Milk-Date Beverage

Abstract

Milk beverage with added natural sweetener is well appreciated by consumers as a nutritious and healthy product with unique sensorial quality attributes. However, this product requires a suitable pasteurization method without significant impact on the sensorial and physicochemical quality characteristics of the product. This study optimizes the pulsed electric filed (PEF) conditions for the pasteurization of a milk-date beverage with conserved physicochemical quality properties. The effect of process variables, such as pulse off time (20, 30, and 40 μs), number of pulses (20, 50, and 80), powder ratio (10, 15, 20, and 25% w/w), storage time (2, 4, and 6 days), and storage temperature (5, 15, and 25 °C) on the responses of total viable count (TVC), color difference (∆E), pH, and total soluble solids (TSS) was evaluated using the RSM central composite design (CCD). Pulse off time, number of pulses, date powder/milk ratio (w/w), storage time, and storage temperature greatly impacted the microbial and physical properties of the beverage. The optimal conditions for decreasing the microbiological load and physical change of beverages were a pulse off time of 40 μs, number of pulses of 80, and storage temperature of 5 °C for all powder ratios. These variables gave a safe beverage for up to six days. At optimal conditions, the values of pH, TSS, ∆E, and TVC were 7.51, 15.44 °Brix, 18.01, and 0.138 Log 10 CFU/mL, respectively, for the powder ratio of 10% (w/w); 7.66, 18.6 °Brix, 21.46, and 0.284 Log 10 CFU/mL, respectively, for the powder ratio of 15% (w/w); 7.56, 21.52 °Brix, 25.24, and 0.577 Log 10 CFU/mL, respectively, for the powder ratio of 20% (w/w); and 7.2, 24.2 °Brix, 29.34, and 0.741 Log 10 CFU/mL, respectively, for the powder ratio of 25% (w/w).