UV-C IRRADIATION OF FRESHLY SQUEEZED GRAPE JUICE AND MODELING INACTIVATION KINETICS

UV inactivation kinetics of freshly squeezed turbid white grape juice (FSTGJ) treated with an annular flow UV reactor by applying UV dosages ranging from 0 to 116.7 J/mL, at three different flow rates (0.90, 1.75 and 3.70 mL/s), were modeled by using log-linear, Weibull, Hom and modified Chick-Watson models. FSTGJ was circulated five times in the UV system, i.e., UV exposure time was 20.33 min during processing. The populations of Escherichia coli K-12, lactic acid bacteria (LAB) and foodborne yeasts were reduced by 3.759, 4.133 and 1.604 log cfu/mL, respectively, after exposure to UV dosage of 116.7 J/mL at the lowest flow rate. The inactivation kinetics of foodborne yeasts were best described by the modified Chick-Watson model, with the least root mean squared error (RMSE = 0.001, R-2 = 0.999). Besides, the inactivation kinetics of E. coli K-12 and LAB were best fitted by Weibull model (R2 = 0.999). Additionally, when the UV exposure time was increased up to 32.5 min (i.e., eight cycles), UV-C treatment of FSTGJ resulted in 5.341 log cfu/mL reduction in E. coli K-12, which meets the Food and Drug Administration requirement of a 5 log reduction of microorganisms in fruit juices.