Ozone Kills E. coli in Ground Beef
The use of gaseous ozone was evaluated as an antimicrobial intervention against Escherichia coli (E.coli) in ground beef. This research took place in two parts. Phase 1 initially inspected for color and appearance change due to ozone gas oxidizing the beef. Phase 2 tested for antimicrobial action due to the ozone against E.coli bacteria. Ozone treatment to the ground beef showed no color or flavor change at ozone levels that were effective at reducing E.coli in the ground beef. Raw, ground beef inoculated with generic E.coli was treated with gaseous ozone at various levels, it was determined that approximately 95.8% of the E.coli in the ground beef was killed when the ozone concentration approached 200 ppm.
Ground beef recalls are commonly caused by unsafe levels of E.coli bacteria found in the product that is distributed to stores. Specifically the O157:H7 strain of Escherichia coli (E.coli) is found in the recalled beef. Currently there are very few antimicrobial intervention options available for the ground beef process. This research was performed to evaluate if there is a possibility that ozone gas may be an effective antimicrobial intervention in the ground beef process.
Ozone has proven to be a very effective antimicrobial intervention in many food processing applications (Rice 1983), including red meat and beef applications. Ozone has proven to be an effective antimicrobial intervention against E.coli,(Akbas and Ozdemir 2006) and specifically O157:H7 E.Coli (Kim and Yousef, 2000). However, ozone is traditionally used in the aqueous phase for surface sanitation and general disinfection. Aqueous ozone is very convenient as an antimicrobial agent, water is the carrier of the ozone. Typically water is already in use in the washing of surfaces and produce, so adding ozone to existing processes is very convenient and cost effective.
While aqueous ozone has proven effective in other beef processing applications, the use of aqueous ozone is not possible in most ground beef processes as water would need to be added to the ground beef mixture, doing so is undesirable as that ground beef will then loose the 100% ground beef rating.
Ozone gas may be an alternative to aqueous ozone in ground beef processing as an antimicrobial intervention. Ozone gas is used as an antimicrobial intervention in other processes with great success, (Rice 1983) and it has been very briefly tested in beef storage application in the past with good results in reducing some strains of bacteria (Fournaud & Lauret 1972). During this past testing, discoloration of the red meat was analyzed. With 100 ppm of ozone exposure at up to 30 minutes, no change in color was noticed. With 500 ppm of ozone exposure for the same time period, undesirable color and odor changes were noticed in the meat samples. The apparent odor change of the meat found in this test provides justification to test for flavor changes in cooked ground beef after ozone treatment.
Due to the lack of conclusive evidence that ozone gas will be effective on ground beef, and limitation of using only ozone gas as an antimicrobial intervention on ground beef, further research is necessary. The previous color and flavor questions that have been raised require testing to ensure that ozone will not affect these qualities of the product. This current two-part research is aimed at evaluating the effect of ozone gas on color and flavor, and then evaluating the effectiveness of ozone gas as an antimicrobial intervention on a ground beef product.
This research was performed as a joint effort between Ozone Solutions, Inc., Synergy Environmental, Inc., and Kraft Science Consulting. Each party contributed considerable time and expense to complete this research and provide the findings.