Current method in plum marmalada production: Ohmic heating

This study investigated the production of plum marmalade using the ohmic heating method and examined the effects of this process on product quality. Initially, the nutritional and technological properties of plums and the marmalade production processes were reviewed in the light of existing literature. It was emphasized that plums are rich in phenolic compounds, antioxidants, and dietary fiber, and that marmalades possess significant potential for the development of sustainable and functional food products. Ohmic heating, which involves the passage of electric current directly through the product, enables rapid, homogeneous, and energy-efficient heating, thereby offering advantages over conventional thermal processes in preserving product quality. In the experimental phase of the study, marmalade was produced using ohmic heating at different voltage gradients (30, 35, and 40 V/cm), and comparisons were made with marmalade produced by traditional methods. The experimental results demonstrated that increasing the voltage gradient significantly reduced both the heating and evaporation times, which in turn contributed to better preservation of total phenolic content (TPC), antioxidant activity (AA), and vitamin C levels. The highest TPC and AA values were obtained at the 40 V/cm voltage gradient. Furthermore, the formation of hydroxymethylfurfural (HMF) in marmalades produced via ohmic heating was found to be lower compared to those produced using conventional methods. An examination of color parameters revealed that higher voltage gradients resulted in decreased total color change (ΔE) values, with products retaining a brighter and more homogeneous color. The rapid heating achieved by ohmic heating reduced thermal degradation of pigments and nutrients, thereby helping to maintain overall product quality. In conclusion, ohmic heating provided notable advantages over traditional methods in plum marmalade production, including shorter processing times, improved nutritional preservation, and enhanced functional properties such as higher retention of phenolic compounds and antioxidant activity. These findings support the potential applicability of ohmic heating technology at an industrial scale.