Impact of pulsed electric field and preheating on the lime purification of raw sugar beet expressed juices

Abstract

This work discusses the effects of pulsed electric field (PEF) and preheating on the lime purification of raw sugar beet expressed juices. The PEF pre-treatment was applied to sugar beet cossettes before their pressing at 20°C with the PEF strength and duration of respectively E=600V/cm and tPEF=10ms. Alternatively, cossettes were preheated at 80°C for 10min before pressing to produce the thermal juice.A lime-carbonation process was applied for the purification of raw expressed juices. The influences of lime quantity (varied from 0 to 15kg/m3) on the filterability and the quality of juices were investigated. It was shown that the filtration kinetics of cold PEF juice is faster than that of thermal juice leading to lower values of filtration coefficient Fk and specific filter cake resistance α. Analysis showed that thin juices obtained after purification of PEF juices presents better qualitative characteristics than those obtained from thermal expressed juices. For instance, at the optimal lime quantity (10kg/m3), the purified PEF juice was less coloured (540 vs. 1360IU), less turbid and had less proteins and colloids leading to a higher juice purity (0.961 vs. 0.945) comparatively to the purified thermal juice.