Improvement of concentration process using ohmic heating in sea buckthorn processing

Abstract

Currently, the market for small and medium-sized farms is highly competitive. To increase the competitiveness of small farms, they should process their products in-house, thereby significantly increasing production profitability. Farms that grow sea buckthorn berries may process them into jelly marmalade. The primary production unit for this type of product is a vacuum evaporator. This unit is expensive making it difficult to implement a full-cycle process at small enterprises. The introduction of new technologies such as ohmic heating for mass concentration is relevant. However, there are currently no studies on the electrical conductivity of jelly masses directly heated in vacuum-operated devices. The study utilized an ohmic heating device operating under vacuum. The conducted studies revealed dependence of the electrical conductivity of the processed product on temperature at varying electric field strengths (10-25 V cm) which was described by a fourth-degree polynomial. It was also found that at the onset of boiling, a sharp decrease in electrical conductivity is observed associated with the formation of "dry spots" on the electrodes due to the accumulation of steam bubbles. This phenomenon significantly increases electrical resistance and reduces the system’s electrical conductivity. The obtained values may form the basis for automation control systems being developed for vacuum evaporators using direct heating of the product for small farms engaged in sea buckthorn growing.