Several-staged alkaline pressing-soaking of electroporated sugar beet slices for minimization of sucrose loss

• Alkaline pressing-soaking of PEF treated sugar beet slices was studied.
• The effective process parameters were defined.
• Alkaline pressing accelerates extraction kinetics and improves juice quality.
• Proposed process minimizes sucrose loss and increases pulp dryness.

In this work, a new process of several-staged alkaline pressing-soaking of electroporated sugar beet slices is proposed and analyzed to minimize the sucrose loss. For this purpose, sugar beet roots were first sliced and electroporated by pulsed electric field (PEF) at ambient temperature with electric field strength of E = 600 V/cm and effective duration of tPEF = 10 ms. The PEF treated slices were then subjected to a double pressing with an intermediate lime milk soaking (using 0.6 g CaO/100 g fresh slices). The obtained limed press-cake was again pressed one or two times with an intermediate water soaking to recover the residual sucrose. The degree of the first pressing U was fixed at 50 or 75%, the expression pressure was varied from 1 to 50 bar, the soaking degree of lime milk α was varied from 0 to 20% and the soaking degree of water β was fixed at 5 or 10%. The total yield of solutes in an optimized four-staged pressing-soaking was 99.53%, the sucrose loss in pulp was 0.23% and the dryness of pulp was 39%. The quality of mixed expressed juice was better that that of the traditional diffusion juice obtained by hot water extraction. Expressed juice was more concentrated (18 vs. 14.5%), had higher purity (93.16 vs. 91.62%), and lower coloration (2619 vs. 9842 IU) than the juice obtained by hot water extraction. The proposed process presents major advantages including cold processing, high pulp dryness, lower quantity of water addition and shorter extraction duration. It seems to be very promising for energy save, environmental protection and bioeconomy in future sugar beet industry.Industrial relevanceConventional sugar beet extraction by hot water is energy costly and produces impure extracts of high coloration. Application of pulsed electric field and following pressing of electroporated sugar beet slices improve juice quality and decrease energy consumption. However, the sucrose losses in pulp remain high. Staged alkaline pressing-soaking of electroporated sugar beet slices investigated and optimized in this study permits minimizing of sucrose losses in pulp, improvement of juice quality and production of the pulp of high dryness.