Comparison of Aqueous Ozone and Chlorine as Sanitizers in the Food Processing Industry

Posted by Wei, Kuangji, Zhou, Hongde, Zhou, Ting and Gong, University of Guelph, Guelph, Ontario, Canada, Ozone Solutions on 18th Oct 2021

Comparing Ozone vs Chlorine as Food Sanitizer:

The effects of ozone treatment on fresh strawberry and shredded lettuce good quality were tested by varying applied ozone concentrations, contact times, pH and temperatures to assess ozone as a potential food sanitizer. The produce quality was assessed by comparing the changes in texture, firmness, browning and decolorization, oxygen consumption and carbon dioxide respiration after the post-treatment storage from 0 to 21 days. The effectiveness of Ozonation on natural microflora including mesophilic, phychotrophes,

yeasts and molds, was also evaluated for the improvement in produce shelf-life. As compared to chlorine treatments, ozone treatments slightly increased the lettuce browning but substantially retarded its respiration rates and firmness deterioration even after 21 days of storage. For strawberry, no significant difference in food quality was observed between ozone and chlorine treatments. Finally, ozone treatments at the doses below 10 mg/L were found not effective in killing natural microflora grown on the produce surfaces.


There are concerns about food quality and microbial safety for fresh agriculture, especially minimally processed produce which have minimal cleaning and sanitization before being consumed. Produce quality can be decreased due to mechanical damage from its handling and processing from the time it is grown till it is purchased by the end user. 

Testing / Method

A test was performed using chlorine and ozone on both lettuce and strawberries to determine their effectiveness in maintaining their quality and natural biological characteristics. By increasing the quality and extending the natural characteristics a better product is available for the market. 

Conclusion / Results

Ozone slowed the respiration rates of lettuce, which can result in extended shelf-life. Both chlorine and ozone did not impact the respiration rate of strawberries, demonstrating that results are produce-specific. Ozone was more effective than chlorine in extending firmness of strawberries and lettuce. Ozone was not shown to be effective in preventing browning of lettuce compared to chlorine and with strawberries there was no change in color. 

Operating Cost of Ozone

Compare the operating cost of ozone vs. bleach and peracetic acid.

Note: For pathogen destruction, 2 ppm ozone is equivalent to 160 ppm bleach, which is also equivalent to 100 ppm PAA. 

Operational Parameters

  • Run Time: 8 hours/day 
  • Operating Days/Week: 5
  • Water Consumption Flow Rate: 4.67
  • Bleach (12% NaOH) Cost: $10/gallon
  • Peracetic Acid (PAA) Cost: $10/gallon
  • Target Bleach Concentration: 160 ppm
  • Target PAA Concentration: 100 ppm
  • Target Ozone Concentration: 2 ppm

Published- Ozone: Science & Engineering, 29:2, 113 - 120