A Thermomechanical Preprocessing for Pectin Isolation from Orange Peel with Optimisation by Response Surface Methodology

Abstract

The instantaneous controlled pressure drop process (or D.I.C process: ``Détente Instantanée Contrôlée") was used as a pre-treatment prior to pectin acid extraction from orange peel. This process involves subjecting the orange peel for a short time to steam pressure varying from 100 to 700 kPa, followed by an instantaneous decompression to vacuum at 5 kPa. Effects of processing pressure, moisture content of peels before the thermomechanical treatment and processing time were examined with response surface methodology. The optimal conditions were determined and the response surfaces were plotted from the mathematical models. The Fisher test and p-value indicated that both processing pressure and moisture content of peels before the pre-treatment had a highly significant effect on the pectin yield. The quadratic effect of processing pressure as well as the interaction effects of the initial moisture content and processing time also had a significant effect on the response. Moreover, the kinetics of pectin extraction showed that after few minutes of hydrolysis, the yields of pectin were systematically higher than that of the control sample and this is important from industrial point of view because the hydrolysis of pectin is generally performed in 10-15 minutes.