Degradation kinetics of ascorbic acid, total phenolic and antioxidant content of sour orange juice during thermal processing

Sour orange is a citrus with high antioxidant content (mainly ascorbic acid and phenolic compound). Its juice is consumed as a food seasoning. Thermal pasteurization is a common way to improve safety of sour orange juice. By considering the high thermal sensitivity of ascorbic acid and phenolic compounds, the aim of this study is the investigation of the effect of thermal processing on ascorbic acid, total phenol and an antioxidant capacity of sour orange juice at 70, 75, 80, 85 and 90 °C in 76, 66, 48, 35 and 21 min, respectively. Ascorbic acid and total phenolic content were measured according iodine titration and Folin- Ciocalteu methods, respectively. Ascorbic acid and total phenol degradation during thermal processing were evaluated by Arrhenius and Eyring models. Enthalpy of ascorbic acid degradation changed slightly due to its high thermal resistance (29.15°C) and free energy (101.11-102.64 kJ/mole). With 5°C increase in temperature, the half-life of ascorbic acid and the total phenol content decreased about 1.31 to 1.80 and 1.39 to 2.05 times, respectively. Also there was a good correlation between total phenol content and DPPH of sour orange juice (R2> 0.97).