Robustness testing of the juice extraction process using a pulsed electrical field

As robustness of any industrial process is an important issue, a standard procedure is used to determine the set point and to minimize the process variability of juice extraction to changes in values of some critical factors. This paper reports work to analyse the efficiency of the pulsed electrical fields carrot juice extraction process even when the control factors undergo slight random variation. The experiments were carried out on a laboratory experimental bench. The work concerned the choice of three factors which are the high voltage level V (kV), the number of pulses and the pulse duration T. Three ‘one-factor-at-a-time experiments’, followed by two factorials designs (one composite, the other fractional), were performed following a well-defined experimental procedure: (1) Fixing the variation domain of the input variables; (2) seeking the optimum set point and (3) analysing the robustness of the process i.e. testing whether the performance of the system remains high even when the factors vary slightly around the set point.