Kinetics of freshly squeezed orange juice quality changes during ozone processing

Freshly squeezed orange juice samples were ozonated with control variables of gas flow rate (0-0.25 L min(-1)), ozone concentration (0.6-10.0%w/w), and treatment time (0-10 min). Effects of ozone processing variables on orange juice quality parameters of pH, degrees Brix, titratable acidity (TA), cloud value, nonenzymatic browning (NEB), color values (L*, a*, and b*), and ascorbic acid content were determined. No significant changes in pH, degrees Brix, TA, cloud value, and NEB (p < 0.05) were found. L*, a*, and b* color values were significantly affected by gas flow rate, ozone concentration, and treatment time. The changes in lightness (L*) values and total color difference (TCD) values were fitted well to zero-order kinetics, whereas a*, b*, and ascorbic acid degradation followed first-order kinetics. The rate constants for a*, b*, and TCD were linearly correlated with ozone concentration (R-2 = 0.88-0.99), whereas the rate constants for L* and ascorbic acid were exponentially correlated (R-2 = 0.94-0-98).