Effects of PEF and heat pasteurization on PME activity in orange juice with regard to a new inactivation kinetic model

Abstract

The inactivation kinetics of pectin methyl esterase (PME) during the shelf life (4°C-180days) of freshly squeezed orange juice samples processed by both pulsed electric fields (PEF) and heat pasteurization (HP) was evaluated in the study. The PME inactivation level after the PEF (25.26kV/cm-1206.2μs) and HP (90°C-20s) treatments were 93.8% and 95.2%, respectively. The PME activity of PEF-processed samples decreased or did not change, while that of HP samples increased during storage (p<0.01). A kinetic model was developed expressing PME inactivation as a function of the PEF treatment conditions, and this enabled the estimation of the reaction rate constant (587.8–2375.4s−1), and the time required for a 90% reduction (De, 3917.7–969.5s). Quantification of the increase in PEF energy to ensure a ten-fold reduction in De (ze, 63.7J), activation electric fields (−921.2kVcm−1mol−1), and electrical activation energy (12.9kJmol−1) was also carried out. Consequently, PEF processing was very effective for the inactivation of PME and for providing stability of orange juice during storage.