EFFECTS OF COMBINED OZONATION AND UV-C TREATMENT OR VAPORED HYDROGEN PEROXIDE FUMIGATION TO INACTIVATE ESCHERICHIA COLI AND ASPERJILLUS NIGER CONTAMINANTS IN RICE NOODLE INDUSTRY

The ability of ozonation and UV-C applied to eradicate total plate count, yeast/mold and Escherichia coli contamination were tested on a flour slurry and to study the application of vapored hydrogen peroxide (VHP) for sanitizing the chamber.

Method: A prototype system, consisting of ozone generator (2 L/min) and UV sterilizer (45 W), was fabricated and tested on flour slurry systems using the same initial E. coli and A. niger concentration. In this experiment, the ratios of flour slurry to water were prepared at 0, 20, 45, 75 and 100%. The flour slurry (15 L) were spiked with E. coli or A. niger at 7 log CFU/mL approximately 200 mL. The circulation mass flow rates were fixed at 0.3 kg/s. Sampling time intervals were 0, 5, 10, 20, 30 and 40 min. Total plate count (TPC), yeast/mold and E. coli was achieved by taking 1 mL aliquot of sample.

Result: The result showed the destruction profiles of TPC, yeast/mold and E. coli counts as a function of time and ratio of flour slurry. After Ozone and UV treatments for 40 min, the TPC, yeast/mold and E. coli counts were reduced to 0 log CFU/mL in the 20% of flour slurry. For the flour slurry concentrations higher than 20%, the ozone with UV treatment was able to bring down the microbial counts to only 3 - 2 log reductions, respectively. In all treatments with 1-5% hydrogen peroxide (H2O2), there was an instant drop of E. coli numbers within the first 2 min from 109 to 105 CFU/mL or 4 log reductions. It was shown that even at shorter time periods could eliminate organisms as long as H2O2 was well distributed and maintained at an effective concentration to destroy E. coli cells. The number of the fungal colonies decreased when the concentration of VHP were increased. When the addition of H2O2 at 3 and 5% concentrations at exposure times of 4-6 min produced incremental increases in A. niger destruction.

Conclusion: The combined ozone/UV treatments have been shown to be more appropriate treatments for cloudy and turbid medium, like flour slurry. The use of combined treatment was able to achieve zero E. coli and A. niger count. For fumigation with VHP, we found that VHP decontamination reduce bacterial and fungal contamination in chamber. H2O2 is easily evaporated or destroyed after use (readily decomposing into water and oxygen), has no unpleasant lingering odor, and poses minimal safety problems for workers if handled properly.