Nonthermal pasteurization of tender coconut water using a continuous flow coiled UV reactor

- Tender coconut water (TCW) was pasteurized in continuous flow coiled UV reactors.
- E. coli were reduced by 5 log CFU/ml at Re number 596 at 802 mJ/ml UV dose.
- L. Monocytogenes were reduced by 4.18 log CFU/ml at Re number 596 at 802 mJ/ml UV dose.
- No significant change in quality of treated TCW observed after 28 days at 4 °C.

A non-thermal pasteurization technology is desirable to naturally preserve nutrient and organoleptic properties of packaged tender coconut water (TCW) distributed under refrigeration. The goal of this research was to assess the antimicrobial effectiveness of ultraviolet light C (UVC) as a non-thermal pasteurization of TCW. A dean flow ultraviolet reactor was used with wavelength of 254 nm at the residence time of 14.0 s. The experimental variables were three Reynold numbers (Re = 198.8, 397.7 and 596.4) and two diameters of transparent PFA tubes (3.2 mm and 1.6 mm). TCW was inoculated with cultures of Escherichia coli W1485 and Listeria monocytogenes separately before passing through the UV reactor. UVC treatment yielded 5.27 and 4.74 log10 CFU/mL E. coli count reductions for 1.6 mm and 3.2 mm ID reactors, respectively, whereas the reduction of Listeria monocytogenes were 4.18 and 2.96 log10 CFU/mL, respectively at Re = 596.4. Furthermore, as the Reynold number increased, microbial reduction also increased. The physico-chemical changes of cold pasteurized TCW were not significantly different compared to the fresh TCW.