Optimization of Thermal and Thermosonication Treatments on Pectin Methyl Esterase Inactivation of Sour Orange Juice (C itrus aurantium )

Abstract

The objective of this study was to analyze and optimize the critical process parameters in inactivation of pectin methyl esterase (PME) in sour orange juice by thermal and thermosonication processes using response surface methodology. A central composite design was employed for experimental design and process optimization. The thermal inactivation of PME was carried out at temperatures between 40 and 80C for 5–25 min. At thermosonication process, temperature and time were kept as before while the process was optimized with an ultrasound intensity of 60–100 W. Simultaneous application of ultrasound and thermal process enhanced the enzyme inactivation. The optimal process condition for PME inactivation in thermal process and thermosonication (at 80 W) were 21.80 min at 75C and 9.8 min at 63C, respectively. The results indicate that thermosonication of sour orange juice could entirely inactivate the PME. Practical Applications Today, preservation by elevation of temperature for short periods of time (up to 90C) is still the most common processing method for microbial or enzyme inactivation that leads to longer shelf life. Because of the exposure to high temperature, this thermal method has disadvantages for many food products particularly fruit juice. The production of new substances from heat-catalyzed reactions and the modification of macromolecules as well as the deformation of plant and animal structures may reduce in a loss of quality. Therefore, thermal treatment can cause undesirable alterations of sensory attributes, i.e., texture, flavor, color, smell and nutritional qualities, i.e., vitamins and proteins. Ultrasound is an efficient nonthermal (minimal) processing alternative.