Impact of short-wave ultraviolet light (UV-C) combined with mild temperature on the inactivation of some microorganisms in carrot beverages

GARCÍA CARRILLO, MERCEDES; FERRARIO, MARIANA; SCHENK, MARCELA; GUERRERO, SANDRA

Chicago

Congreso; Institute of Food Technologists. Annual Meeting 2016.; 2016

Institute of Food Technologists

UV-C has significant promise to reduce the microbial contamination levels for a wide range of beverages. Due to the presence of color compounds and suspended aggregated particles, many fresh juices transmit relatively little UV light, and consequently, the efficiency of the pasteurization process is reduced. The aim of this study was to evaluate the inactivation of Escherichia coli ATCC 35218, Saccharomyces cerevisiae KE162 and Pseudomonas fluorescens ATCC 49838 in fresh filtered carrot juice (CJ, muslin cloth, pHadj: 5.0, 7.1 °Brix, Ɛabsorptivity: 0.26 cm-1, turbidity: 7167±5 NTU, particle size= D[3,2]: 4,6±0,4 µm, D[4,3]: 29,30±4,39 µm) processed by UV-C light at 20 °C. In addition, combined treatments involving UV-C and mild temperature were also evaluated in fresh filtered carrot-orange juice blend (COJ, 1:1 ratio (v/v), pHadj: 5.0, 10.6 °Brix, Ɛabsorptivity: 0.32 cm-1, turbidity: 7667±15 NTU, particle size= D[3,2]: 5.1±0.1 µm, D[4,3]: 60.81±8.68 µm). Juice (750 mL) recirculated through an annular reactor consisting of two serially connected UV-C lamps during 15 min (1.6 L/min, 0.0-11.4 kJ/m2, T=20, 40 or 50 °C). After 20 °C UV-C exposure, 2.7-4.1 log-reductions were obtained in CJ while 2.0-2.9, in COJ, being E.coli and P. fluorescens more sensitive than S. cerevisiae. Lower absorbance (Ɛabsorptivity), aggregation (D[4,3]/ D[3,2] ratio) and turbidity of CJ compared to COJ, could be responsible for the observed higher inactivation in CJ. Notwithstanding, single UV-C inactivation improved with mild temperature, changing the inactivation curve shape, but, microbial resistance thermodependence differed among species. In COJ, mild heat treatments were ineffective (< 0.6 log-reductions) while 2.67-6.04 log-reductions were achieved with UV-C/T treatments, thus observing additive and even synergistic effects. Weibull and modified Gompertz models were successfully used to complementary characterize microbial inactivation (R2adj: 97.0-99.5). Modified Gompertz model better described UV-C/T inactivation curves, which exhibited sigmoid shape. Single UV-C weibullian frequency distributions were skewed to the right, with high variance, tail and, excepting for S. cerevisiae, without mode. Combined UV-C/T treatments (40 °C and 50 °C) generated narrower frequency distributions more skewed to the right, with low variance, mean and without mode and tail. This study gives useful quantitative information regarding the effect of UV-C treatment for carrot derivates.