Effect of ohmic heating on bioactive components of apple juice

Ohmic heating application is one of the innovative food processing techniques based on the conversion of electrical energy into heat energy, which has application areas in foods such as pasteurization, sterilization, thawing, boiling, cooking, distillation, extraction, evaporation. In this study, it was aimed to determine the potential of heat treatment with ohmic heating and to compare it with conventional heat treatment in maintaining the general quality of apple juices rich in bioactive components (total phenolic substance, total flavonoid substance, antioxidant activity). Within the scope of the study, the kinetic modeling of some of the changes in these properties of apple juice was also carried out. Total phenolic content, total flavonoid content and antioxidant activity values of fresh apple juices prepared from concentrated fruit juice were 19.38±0.53 mg GAE/100 mL, 2.96±0.10 mg CE/100 mL and 12.05±0.17 µmol TE/100 mL, respectively. It was determined that these values were 16.75±0.90 mg GAE/100 mL, 2.48±0.36 mg CE/100 mL and 4.66±0.17 µmol TE/100 mL, respectively, in samples exposed to ohmic heating for 30 minutes at a voltage gradient of 10 V/cm at 80°C. These values were 15.14 mg GAE/100 mL, 2.55 mg CE/100 mL and 4.67 µmol TE/100 mL at a 20 V/cm voltage gradient. In conventional heating (water bath), they were found as 16.94±0.19 mg GAE/100 mL, 1.98±0.03 mg CE/100 mL and 10.80±0.97 µmol TE/100 mL, respectively. When the variation of browning index with time was determined, it was found that there was a statistically insignificant difference (p˃0.05).