Application of advanced oxidation processes (ozone/UV) to reduce Escherichia coli contamination in flour slurry from rice noodles production

Abstract

This paper aimed to demonstrate another potential use of AOPs for reclaiming flour slurry
from rice noodle making process by destroying spoilage microorganisms and preventing
further microbial growth using Escherichia coli as a model microorganism. A prototype
AOPs system, consisting of UV sterilizer (45 W), ozone generator (2 L/min) and combined
ozone/UV, was fabricated and tested on water and flour slurry (53 g/L) systems using the
initial E. coli concentration at approximately, 7 log CFU/ml. The E. coli cell counts showed
that UV disinfection was very effective in water, enabling the reduction of cell density from 7
to 0 log CFU/ml within 15 min at all mass circulation flow rates (0.4, 0.6, and 0.8 kg/s). For
flour slurry, the blockage of UV radiation by flour suspension substantially compromised the
effectiveness of UV sterilization and E. coli destruction. Although, the ozone treatment by
itself showed slower E. coli inactivation kinetics on both transparent and turbid flour slurry,
it produced powerful disinfecting effect when it installed prior to the UV sterilizer. The
synergic combination of UV and ozone treatments in inactivating E. coli was demonstrated
on the flour slurry experiment and able to eliminate E. coli viability within 8-10 min. Faster
mass circulation rate facilitated higher E. coli elimination due to higher UV exposure of E. coli
and better mixing/dissolution of ozone gas in flour slurry.