Ozone is an effective oxidant on the following microorganisms which are relevant to flour processing: • Salmonella family. • Staphylococcus Aureus (Golden Staph) • Clostridium tetani. • The OSI database does not have direct evidence for Clostridium Peifringens, but we believe it would react similarly a both are rod shaped bacteria from the same genus. • Coliforma (Coliforms). Our OSI database has much evidence for Bscherichia Coli (B. Coli) which is the most common of the Coliforms. • Various yeasts. • Various moulds.
A. MICROBIAL PROPERTIES OF OZONE ON CEREAL GRAINS, CEREAL GRAIN POWDERS, PEAS, BEANS AND WHOLE SPICES
In order to study the food preservative effect of ozone, microbicidal effect of ozone was investigated employing cereal grains, cereal grain powders, peas, beans and whole spices. The conditions employed to evaluate the microbicidal effect were: ozone gas concentration 0.5 ~ 50 ppm, temperature 5 ~ 50oC, time 1 ~ 6 hours and flow rate 100 L/min. Results were as follows:
The microbicidal effect of ozone was affected by contact concentration. Higher contact concentration resulted in greater microbicidal effect on various cereal grain powders. When buckwheat whole grain with hull (Japan), black matpe and black pepper (seed) were treated with 5.0-ppm ozone, microbicidal effect of ozone was maximum.
Whole, halves and ground samples of buckwheat were treated with 50 ppm ozone continuously for 1 hour at 10oC. Microbicidal effect of ozone was maximum in whole and minimum in ground.
Lower temperature resulted in the greater microbicidal effect on cereal grains, cereal powders, peas, beans and whole spices except black pepper.
Longer contact time resulted in the greater microbicidal effect on cereal grains, cereal grain powders, peas, beans and whole spices except buckwheat whole grain with the hull and black matpe.
B. OZONE TREATMENT FOR FLOUR PROCESSING ( The difference between Chlorine dioxide and Ozone)
Chlorine Dioxide and Ozone destroy micro -organisms using identical methods. The relevant chemical feature, which results in sterilisation, is that both are oxidants. Both have high ‘electro-negativity”. Therefore when oxidising hydrocarbons (H+C) or hydrocarbonates (H+C+O) they reduce the carbon atom’s “ownership” of its electrons. The oxidation effect is that the wall of simple cellular microorganisms (e.g. bacteria) and the protein coating around non-cellular microorganisms (e.g. viruses) is ruptured. The three-dimensional structure of bonds in amino acid chains, is also “denatured”. Simple microorganisms cannot repair this damage and they die. (Note those complex large cells, such as human cells and animal cells are not affected in this manner).
Ozone and Chlorine Dioxide differ in important ways:
1. half life effect.
2. need to manufacture on-site.
3. oxidising strength.
4. oxidising speed.
1. Ozone has a very short half-life. In a typical ambient environment it is approximately 1 hour – in which case its concentration in air will halve every hour. Therefore, in a relatively short time, residual Ozone will completely disappear, as all “unused Ozone” (0 3) reverts back to diatomic oxygen (0 2). Therefore after the treatment and storage of the flour, there will be no chemical residue whatsoever. Chlorine Dioxide however leaves a definite chemical residue.
2. Ozone’s short half-life is unique amongst commercial oxidants, disinfectants and sterilants. One practical implication of this, is that it needs to be generated on-site, and cannot be purchased in bottles. Due to technical improvements in recent years, this can now be achieved economically and in high concentrations, using Ozone generators such as Airzone. Generating on site also avoids the Occupational Health and Safety issue associated with the transport, handling and storage of hazardous chemicals.
3. The normal oxidation potential of Ozone is approximately 1.5 times that of Chlorine or Chlorine Dioxide. Therefore, lower ppm concentrations are possible by using Ozone compared to Chlorine based oxidants. If Chlorine Dioxide is used at 150 ppm, then as a guideline 100-ppm of Ozone is equivalent (everything else held constant).
4. Ozone reacts up to 3000 times faster than chlorine based oxidants with organic matter such as bacteria. Chlorine Dioxide reacts very slowly by comparison and typically requires a long residence time whilst the flour is “agitated” and gas/particulate mixing takes place. In the case of Ozone, good mixing and agitation is still required. Ozone, like most gaseous oxidants, acts on the surface of large particles, and mixing ensures it contacts these surfaces. However, the residence time itself is not required. Often, a long residence time is not practical in a flour processing line, as it is difficult or expensive to keep the flour agitated for a long period of time. Therefore to counteract this, the concentration of Chlorine Dioxide is increased to very high levels such as 150 ppm. , because the higher the concentration, the shorter the residence time required, for the same oxidation effect. Ozone concentrations can thus be lower than Chlorine due to this residence time effect. A rule of thumb might be 1:2 to 1:6, although this depends very much on conditions.
The combination of Ozone’s greater oxidation strength and faster reaction time means that significantly lower concentrations can be used compared to Chlorine Dioxide.
Virtually all oxidants include trace elements of other substances (during their generation and their reaction). The presence of trace elements such as NO X’s in the case of Ozone is generally considered to be irrelevant in most commercial applications. It is for this reason and others that the USA FDA recently recognised ozone as having a “safe status” specifically for use in the food industry’, following exhaustive analysis by the relevant sponsoring bodies.
Ozone is an effective oxidant on the following microorganisms which are relevant to flour processing:
- Salmonella family.
- Staphylococcus Aureus (Golden Staph)
- Clostridium tetani.
- The OSI data base does not have direct evidence for Clostridium Peifringens, but we believe it would react similarly a both are rod shaped bacteria from the same genus.
- Coliforma (Coliforms). Our OSI data base has much evidence for Bscherichia Coli (B. Coli) which is the most common of the Coliforms.
- Various yeasts.
- Various moulds.
Ozone is an ideal disinfectant for use in flour processing. As rule of thumb concentrations up to 50 ppm are sufficient.
For example a suitable Airzone generator will have a nominal performance of 24 ppm at 50 litres per second airflow rate, or 50 ppm at around 20 litres per second (by reducing the input flow).
The number of Airzone’s used depends on the flow rate of air in the system. Alternatively if a volume of air can be assumed and the “air changes per hour” in the system is known, the flow rate is then calculated. We can then “size up” the system and recommend the number of units.
An alternative to “sizing” is to start with 2 Airzone units set at full output, and to conduct plate counts for upstream and downstream flour. If a satisfactory result is achieved, the output levels can be tried at a lower setting. If the result is unsatisfactory, further units can easily be added.