Pressure and temperature stability of water-soluble antioxidants in orange and carrot juice: a kinetic study

The stability of water-soluble antioxidant in orange and carrot juice was studied on a kinetic basis during thermal (75-120degreesC) and high pressure (100-800 MPa; 30-65degreesC) treatments. The water soluble antioxidant capacities of both orange and carrot juice, determined using the TEAC number, increased for the first 60 min and 90 min of thermal treatment respectively. These increases can be described by a first order reaction model. The increases in antioxidant capacity became sharper as the temperature was increased, and the estimated Ea values were 79.00+/-7.83 and 40.46+/-8.43 kJ mol(-1) respectively for orange and carrot juice. During the high pressure treatments, a decrease in TEAC number was noticed for the antioxidant capacity of orange juice, and an increase in TEAC number for carrot juice. A first order reaction model was applied to estimate the rate constants. At all of the temperatures studied, the antioxidant capacity of orange juice decreased more quickly as the pressure was increased. On the other hand, the increase in the antioxidant capacity of carrot juice was slowed down by a pressure increase at temperatures above 40degreesC.