Optimization of ohmic heating parameters for rapid pasteurization of sugarcane juice

Abstract:

Sugarcane juice spoils within hours of extraction unless heat-treated, yet conventional pasteurization at 72 °C for 15 seconds often darkens the juice and degrades its fresh flavour. Ohmic heating, where an alternating electric current passes directly through the liquid, raises temperature uniformly and rapidly without hot surfaces. This research optimized voltage gradient (20-50 V/cm), electrode gap (2-6 cm), and initial juice concentration (14-20 °Brix) for ohmic pasteurization of sugarcane juice in a lab-scale static cell. Trials were conducted from April to October 2023 at Federal University of Viçosa, Viçosa, Minas Gerais. A voltage gradient of 40 V/cm with a 4 cm electrode gap and 16 °Brix juice reached 72 °C in 18 seconds roughly four times faster than a water-bath control. At this setting, total plate count fell by 4.6 log cycles and yeast-and-mould count by 3.5 log cycles. Colour retention (ΔE = 2.3) and ascorbic acid retention (87.4%) both exceeded those of water-bath pasteurized samples. Electrical conductivity increased linearly with temperature (R² = 0.98), confirming predictable heating behaviour. These results point to ohmic heating as a viable rapid pasteurization method for small-scale sugarcane juice vendors.