Iranian Research Organization for Science and Technology (IROST) Innovative Food Technologies 2783-350X 12 4 2025 05 31 Black Grape Juice Concentration via Ohmic-Vacuum Hybrid Heating: Quality Parameters, Energy Consumption and Exergy Efficiency Black Grape Juice Concentration via Ohmic-Vacuum Hybrid Heating: Quality Parameters, Energy Consumption and Exergy Efficiency 321 337 1549 10.22104/ift.2025.7587.2212 FA Nazila Zandi Department of Biosystems Engineering; Faculty of Agriculture; University of Kurdistan, Sanandaj, Kurdistan, Iran Jalal Khodaei Department of Biosystems Engineering; Faculty of Agriculture; University of Kurdistan, Sanandaj, Kurdistan, Iran Hosain Darvishi Department of Biosystems Engineering; Faculty of Agriculture; University of Kurdistan, Sanandaj, Kurdistan, Iran Nasser Behroozi-Khazaei Department of Biosystems Engineering; Faculty of Agriculture; University of Kurdistan, Sanandaj, Kurdistan, Iran Mahmoud Koushesh Saba Department of Horticultural Science, Faculty of Agriculture, University of Kurdistan, Sanandaj, Kurdistan, Iran Journal Article 2025 05 01 In this study, the concentration process of black grape juice using a combined vacuum ohmic heating system was investigated, focusing on the effects of pressure parameters (50, 70, and 100 kPa) and voltage gradient (10, 20, and 30 V/cm) on processing time, specific energy consumption, exergy efficiency, and quality parameters (pH, total phenolic content, and antioxidant activity). The results indicated that increasing the voltage gradient significantly enhanced the heating rate and reduced processing time, while the combination of ohmic heating with vacuum (at 75 and 50 kPa) increased processing time. Specific energy consumption at atmospheric pressure (100 kPa) varied between 1.92 to 2.27 MJ/kg water, while reducing the pressure to 50 kPa led to an increase in specific energy consumption by 4.42 to 5.54 times. The highest exergy efficiency (18.78%) was observed at 100 kPa and a voltage gradient of 30 V/cm. In terms of quality, the reduction in pH (up to 16%) and the retention of total phenolic content (857 mg GAE/100 ml) and antioxidant activity (IC50 = 19.36%) at 50 kPa and a voltage gradient of 10 V/cm yielded the best quality results. Based on the findings, it can be suggested that optimizing the concentration process by selecting appropriate levels of pressure and voltage gradient to achieve a balance between energy efficiency and product quality could be explored in future studies. In this study, the concentration process of black grape juice using a combined vacuum ohmic heating system was investigated, focusing on the effects of pressure parameters (50, 70, and 100 kPa) and voltage gradient (10, 20, and 30 V/cm) on processing time, specific energy consumption, exergy efficiency, and quality parameters (pH, total phenolic content, and antioxidant activity). The results indicated that increasing the voltage gradient significantly enhanced the heating rate and reduced processing time, while the combination of ohmic heating with vacuum (at 75 and 50 kPa) increased processing time. Specific energy consumption at atmospheric pressure (100 kPa) varied between 1.92 to 2.27 MJ/kg water, while reducing the pressure to 50 kPa led to an increase in specific energy consumption by 4.42 to 5.54 times. The highest exergy efficiency (18.78%) was observed at 100 kPa and a voltage gradient of 30 V/cm. In terms of quality, the reduction in pH (up to 16%) and the retention of total phenolic content (857 mg GAE/100 ml) and antioxidant activity (IC50 = 19.36%) at 50 kPa and a voltage gradient of 10 V/cm yielded the best quality results. Based on the findings, it can be suggested that optimizing the concentration process by selecting appropriate levels of pressure and voltage gradient to achieve a balance between energy efficiency and product quality could be explored in future studies. https://jift.irost.ir/article_1549_c88d8d0a6097754525e02c2246d8d27f.pdf