PEF PRE-TREATMENT FOR A CONVECTIVE TWO-STEP DRYING PROCESS

Scientists from Elea and the University of Natural Resources and Life Sciences (BOKU) Vienna have published a paper on Convective Two-Step Drying Process with pulsed electric field pre-treatment.

Available literature and previous studies focus on the Pulsed Electric Field (PEF) parameters influencing the drying process of fruit and vegetable tissue. This study investigates the applicability of PEF pre-treatment considering the industrial-scale drying conditions of onions and related quality parameters of the final product. First, the influence of the PEF treatment (W = 4.0 kJ/kg, E = 1.07 kV/cm) on the convective drying was investigated for samples dried at constant temperatures (65, 75, 和85°C)和干燥剖面(85/55, 85/65, 和85/75°C). These trials were performed along with the determination of the breakpoint to assure an industrial drying profile with varying temperatures. A reduction in drying time of 32% was achieved by applying PEF prior to drying at profile 85/65 °C (target moisture ≤7%). The effective water diffusion coefficient for the last drying section has been increased from 1.99 × 10−10m2 /s ~ 3.在pef处理过的组织中,面积为48 × 10−10 m2/s. 在85/65°C干燥剖面情况下, the PEF-treated sample showed the highest benefits in terms of process efficiency and quality compared to the untreated sample. A quality analysis was performed considering the colour, 大量的水泡, 丙酮酸含量, and the rehydration behaviour comparing the untreated and PEF-treated sample. The PEF-treated sample showed practically no blisters and a 14.丙酮酸含量高5%. Moreover, the rehydration coefficient was 47% higher when applying PEF prior to drying.
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