Quality Enhancement of Rhubarb (Rheum ribes L.) Jam by Ohmic Heating

This study aims to comparatively investigate the production of jam from Rheum ribes L., a plant known for its functional properties, using both conventional and ohmic heating methods, and to evaluate the effects of these methods on quality parameters. Ohmic heating was applied at three different voltage gradients (25, 30, and 35 V/cm) and compared with conventional heating. In both methods, jam samples were produced until they reached a total soluble solids (TSS) content of 66%, after which total phenolic content (TPC), antioxidant activity, ascorbic acid (vitamin C), hydroxymethylfurfural (HMF), and individual phenolic compounds were analyzed. According to the results, the highest TPC (488.37 mg gallic acid equivalent [GAE]/kg), antioxidant activity (595.6 mg ascorbic acid equivalent [AAE]/kg), and vitamin C content (23.6 ppm) were obtained at 35 V/cm. In contrast, the conventional method yielded significantly lower values for these parameters and a higher HMF content (29.9 ppm). Ohmic heating enabled a much shorter processing time, reducing energy consumption by approximately sixfold and contributing to better retention of nutritional components. Additionally, higher voltage gradients resulted in improved preservation of individual phenolic compounds (such as gallic acid, catechin, and rutin). The findings indicate that, compared to the conventional method, ohmic heating offers higher efficiency, better retention of bioactive compounds, and a more sustainable production approach due to its lower energy requirement.