Purification of juices obtained with innovative pulsed electric field and alkaline pressing of sugar beet tissue

This work investigates the purification of juices obtained with innovative pulsed electric field treatment and alkaline pressing of sugar beet tissue. Sugar beets were first sliced into cossettes and treated by pulsed electric field (PEF) at ambient temperature with a strength of E = 600 V/cm and an effective duration of tPEF = 10 ms to electroporate cell membranes. Electroporated cossettes were then subjected to a double pressing with intermediate preliming using 0.6 g CaO/100 g fresh cossettes to produce mixed prelimed juice (MPJ). Alternatively, electroporated cossettes were pressed without preliming to produce non-limed raw juice (RJ). MPJ and RJ were then purified by liming-carbonation and alternatively by stirred ultrafiltration. Preliming of electroporated cossettes improves filtration and sedimentation characteristics of juices. Moreover, the overall lime quantity required for the liming-carbonation was lower for MPJ (6 kg/m3) than for RJ (10 kg/m3). Purified MPJ had a high purity (95.4%), low coloration (570 IU), and low content of colloids (0.95 g/L) and proteins (104 mg/L). Alternatively, non-stirred and stirred ultrafiltration of centrifuged MPJ and RJ were studied using PES membranes with MWCO 10-100 kDa. Specific resistance of deposits and ultrafiltration kinetics were evaluated, as well as the qualitative characteristics of obtained permeates and retentates. Ultrafiltration permits decreasing even more the overall quantity of lime used for MPJ purification. However, the quality of MPJ and RJ permeates was lower than the quality of the same juices purified by liming-carbonation. Results of this work show important advantages of the new sugar beet technology combining pulsed electric field treatment and alkaline pressing.