This study investigated the efficacy of ozone washing appliances for microbial decontamination of tomatoes and green onions. Produce were submerged for light or heavy washing in ozone Washer-A or -B (Washer-B generates higher levels of ozone and agitation) or non-ozone Washer-C. Ozone washings reduced total aerobic mesophile counts on whole tomatoes but not green onions when compared to unwashed samples. Washer-B at heavy setting reduced coliform numbers on whole tomatoes by 1.9 cfu/g. Furthermore, Washer-B yielded more than 2.0 log reductions of Escherichia coli (inoculation level at ∼6.3 log cfu/g) on the edible portions of tomatoes than Washer-A at comparable settings. A follow-up study using Washer-B showed that ozone application can significantly reduce E. coli and Salmonella in produce wash water to prevent cross-contamination. However, when compared to non-ozone washing of produce, improved reduction of natural and artificially inoculated microorganisms by ozone applications was not found. Microscopic observation corroborates microbial enumeration showing that removing inedible portions (stem scars or root bulbs) of washed tomatoes and green onions is beneficial for microbial decontamination.
PRACTICAL APPLICATIONS
Contaminated produce is a major cause of bacterial-related foodborne illnesses in the U.S.A. To meet consumer’s demand for safer produce, effective sanitizing methods need to be developed and verified. Data from this study expands our knowledge of ozone-based kitchen appliances for produce sanitization and their practical value for preventing cross-contamination during produce washing. Furthermore, the findings highlight the importance of removing stem-scar and root bulb portions of washed produce for food safety.
Last week I finished the installation of an Ozone System for room disinfection. The purpose of this Ozone System is to generate and control a high gaseous ozone level inside of 10 rooms for disinfection purposes. Using ozone in the gaseous form is always tricky due to safety concerns. Also, ozone gas is very unstable, and can cause difficulty measuring the ozone, and keeping it away from unwanted areas.
This Ozone System uses an Air Sep Oxygen Concentrator to provide oxygen, and two TG-40 Ozone Generators produce 100 g/hr of ozone for this application. A large control box is used to regulate ozone levels and distribute this ozone to 10 separate rooms. A timer is used to allow the user to control the time that ozone is delivered to the rooms, this ensures no personnel are within the area during operation. Ozone Monitors are used to measure ozone in each of the rooms. User settable relays integrated into the Ozone Monitors allow the user to set ozone levels, solenoid valves will then open and close based on these settings to start and stop ozone flow to each room. Flow meters are installed to ensure adequate ozone flow, and to regulate ozone flow to each of the 10 rooms. This allows the user to deliver more ozone to one room than another. A data logger is also used to log all ozone levels. This data logger is equipped with an Ethernet connections allowing the users to see the ozone levels real time from any location from their personal computer.
To measure and control ozone, ten ES-600 ozone meters are used. This is a cost effective and reliable Ozone Monitor for these applications. This was chosen due to the functions included on this monitor, and the long term sensor costs. This Ozone Monitor uses a 0.1 ppm safety relay that cannot be changed. This allows a safety relay to be integrated that will set a safety light to alert personnel that ozone levels are above the 0.1 ppm level. A second relay is used to allow the user to set ozone levels from 0-20 ppm. This relay is set with simple push buttons accessed by easily removing the cover.
Long term costs of this Ozone Monitor are also low. No calibration is ever necessary of the ozone sensor, and the sensors never need to be sent back to Ozone Solutions. The entire sensor is replaceable with a pre-calibrated sensor. When the new pre-calibrated sensor module is installed, the old sensor is disposed of. As the pre-calibrated sensor module carries a cost of $150, this is a very low cost Ozone Monitor to maintain over the long term.
This week last week I was in Georgia installing and performing start up on a few Ozone Systems. These are pictures of an installation of a Waterzone-20 Ozone Injection System for use in a chicken processing plant. This system was installed above the production line in a clean, dry storage room.
This system is used to inject water into ozone for salmonella destruction on chicken. Chicken breasts are passed on a conveyor under a spray bar of aqueous ozone. Water is injected with ozone to maintain a 2 – 3 ppm ozone residual in the water. This is measured and controlled by the AS-500 Dissolved Ozone Meter installed on the system. Water is plumbed with stainless steel piping into the Ozone System, then down to the processing area below where the chicken breasts are sprayed with aqueous ozone.
Ball valves and a sample port have been installed by the customer to by-pass the Ozone System and adequately verify dissolved ozone levels in the water.
The Waterzone-20 Ozone Injection System can be turned ON and OFF remotely by the operators in the processing room below. Connections are provided in the Waterzone-20 to start and stop the system, and also to verify there are no alarm conditions causing the dissolved ozone level to be low.
Research conducted by Ozone Solutions in conjunction with Kraft Science Consulting, and Synergy Environmental proved that gaseous ozone has the potential to be used as an antimicrobial agent against E.coli on ground beef. Read the abstract to this paper here: Abstract: 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
This preliminary research did show that ozone is effective at rendering E.coli inactive on ground beef. While additional testing may be necessary, this initial research has laid the groundwork for a potentially new application of ozone and a method of removing E.coli from ground beef without adding water in the process.
Here is an interesting chart for you. This shows the solubility of ozone into water at varying temperatures. This a great way to illustrate how much of a difference temperature plays on dissolved ozone levels.
Several conclusions can be postulated from the chart. They are the following:
lower temperature permit higher dissolved ozone concentrations
higher ozone concentrations in the ozone gas permit higher dissolved ozone concentrations
Ozone Solubility vs. Temperature is a linear relationship with virtually no ozone solubility above 43-deg C (110-deg F)
Just how soluble is ozone?
Ozone is extremely soluble! At 25 deg C, ozone solubility is 109 mg/l. The solubility of oxygen is 8 mg/l. Ozone is 13 times more soluble than oxygen.
A quick lesson on the chemistry of Ozone. The video below is a taping of Dr. George Kraft of Kraft Science & Consulting speaking on the chemistry of ozone. This is a very educational video.
A few more pages on the chemistry of ozone are below:
Newly added to our rental line, a 300 g/hr ozone generation and injection system. This is a skid mounted turnkey ozone injection system capable of injecting 300 g/hr of ozone into 200 GPM of water. This is a great opportunity to determine if ozone is right for your application.
To see all the details click HERE
To see our complete ozone equipment rental line, click here.
Recently a number of documents have appeared on the Web detailing how to build or procure inexpensive high-flow ozone destruct units. These inexpensive designs are advertised as a cost-effective means to ozone-free rooms or enclosures for microarray applications and seem like a cost-effective alternative to an NT-70 Ozone Destruct Unit.
You may be comparing the price of a high-flow ozone destruct unit like the NT-70 and wondering about any differences besides the price. Consider a number of limitations and significant vulnerabilities inherent to the design of these kludge-type, do-it-yourself units:
Loose Design Tolerances
The “Ozone Annihilator” design does not use any padding or seal between the destruct media and chassis. The wiring is messy and haphazard. Although the document may accurately claim that these units have been tested to reduce ozone levels sufficiently, there is no proven testing yours will perform consistently. A minor flaw in construction or a single component failure could significantly change the unit’s performance.
Portability
The probability of wiring problems or component failures will increase if a home-made unit is transported from one location to another. The NT units are lightweight and can easily be moved from one location to another. Their small size also ensures they do not take up too much room on work benches.
Comparison
By contrast, the Ozone Solutions’ line of Ozone Interceptors (NT-40: $995, NT-70: $1195) are built from a refined design; engineered to optimize flow and destruct efficiency. Every unit is fully portable and includes a three-year manufacturer warranty. The NT line of units have a reputation of strong performance for microarray applications.
This first video is a typical ceramic bubble diffuser. This is a 80 micron diffuser. The gas flow is altered from very low, 1 LPM to a max flow of 10 LPM. This shows that the ceramic diffuser creates very small bubble size at low flow rates, however the bubble size increases as the flow rate increases. This shows the importance of using these diffusers only within the rated flow rates.
This second video is of the porous PTFE tubing bubbling ozone into water. This tubing creates bubbles about 100 micron in size. While PTFE tubing will have a long life, and will prevent any buildup or contamination to the diffuser over time, it does create the largest bubbles of the diffusers in our test.
This last video is of a stainless diffuser with a 20 micron rating. This video shows a range of flow from 20 SCFH, to 180 SCFH (3 CFM). This clearly shows that the smaller micron rating creates much smaller ozone bubbles in the water.
While all these diffusers have pro’s and con’s these video’s give a very informative visual as to the operation of these differs in water. We hope this information helps you make decision on the best possible diffuser for your application.
Did you know that the ozone industry has their own association?
The International Ozone Association (IOA) was formed in 1973 to provide the ozone industry with a central data base of ideas, technical documents, and communication.
The International Ozone Association consists of 3 regional groups, the Pan American Group (PAG) that serves all of North, Central, and South America, the Nippon Islands Group (NIG) that serves all of Japan, and the European African Australasian Group (EA3G) that serves the rest of the world.
The IOA also holds conferences every 2 years with the entire International Ozone Association, and each regional group has annual conferences. These conferences are a great opportunity to learn more about ozone, the products that various manufacturers produce, and meet many people within the industry that are willing to share information about ozone.
There are many benefits to joining the IOA, and most can be found here. My personal favorite benefit is the access to every white paper that has been published by the IOA since 1973. These are now searchable and available for all IOA members.
For more information about the International Ozone Association, please view the IOA website HERE.
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