---

The Juice clarification is an important operation in the fruit processing industry. Sour Orange is a source of vitamin C that is cultivated in the north of Iran. Since turbidity of this fruit after juice extraction affects on quality, shelf-life and concentration of juice; clarification and removing of turbidity-causing factors is important. In this study, the effect of membrane parameters including pressure (1.2-2.2 bar) and temperature (25-35 ºC) on the quality characteristics of sour orange during membrane clarification was investigated. The response surface methodology (RSM) by Design-Expert Software was used to optimize the clarification conditions. Results of the experiments showed that the Browning index was raised by increasing of temperature, but vitamin C content, Total antioxidant activity value and clarity was decreased in this condition. The Browning index was decreased by increasing of pressure; however, no significant effect was observed on the other quality characteristics. Results of process optimization indicated that the best condition to maximize of vitamin C content, total antioxidant and clarity and to minimize of Browning index achieved at 25 ºC and 1.7 bar. In this condition the vitamin C content, Browning index, Total antioxidant activity and clarity was 24.9 (mg/100 cc juice), 0.106, 87.97% and 97.1%, respectively.

---

Sour orange juice has found application in various foods as alternative of lime juice, due to its desirable taste. Different thermal processes could be performed to improve safety and shelf life of this product. In this study, the sour orange juice was processed at four microwave power levels (170, 340, 510 & 680 W) in a various periods of time to reach the product temperature to 72^˚C. The aim of this study was to investigate the effect of heating processes on the some physicochemical properties of sour orange juice during come up time. Based on the results, different power levels of microwave have no significant effects on viscosity. The thermal destruction of Ascorbic acid and Pectin methyl esterase were found to follow first order kinetics. Destruction rate of these two compounds were also increased by increasing microwave power. Because of the effect of microwave power on chemicals especially ascorbic acid, the colorimetric parameters of the product changed as a result of changing in microwave power. By considering the high regression (R²> 0.97) between two measuring methods (spectroscopy and image processing), the image processing method is suggested as browning index during thermal processing.