Ozone sterilization is one of the cold sterilization technologies used by the modern food industry. Because of its high efficiency, pollution-free, and low-cost characteristics, it is highly valued by more and more food companies. Using ozone for space sterilization and disinfection is one of the most widely used forms of use by companies.
How can we use ozone for space sterilization more effectively and avoid some misunderstandings? WONE shares some usage experiences with you.
01
Ozone sterilization principle
Ozone sterilization or its antibacterial effect is usually a comprehensive result of physical, chemical, and biological aspects. To kill bacteria and mold microorganisms, ozone first acts on the cell membrane, causing damage to the cell membrane structure, leading to metabolic disorders and inhibiting its growth. Ozone continues to penetrate and destroy lipoproteins and lipopolysaccharides in the membrane, changing cell permeability, and leading to cell lysis and death.
02
Reference concentration of ozone for space deodorization
Note: The above table is from “Ozone Technology and Application” (Chemical Industry Press, 2003.3)
Air disinfection
- Should be carried out in a closed space with no one indoors. The general ozone concentration is 5mg/m~30mg/m, the relative humidity is 70%, and the action time is 30min~120min.
Water disinfection
- When used for domestic drinking water disinfection, the contact time between ozone and water before the water leaves the factory should be >12 mn, the residual ozone in the water after disinfection should be ≤0.3 mg/L and the residual ozone in the water at the end of the pipe network should be >0.02 mg/L.
Disinfection of tableware and food processing pipelines
- When immersion disinfection is carried out, the general ozone concentration in water should be >10mg/L and the disinfection time should be >15 min; when flushing disinfection is carried out, the general ozone concentration in water should be >0.6 mg/L, and the disinfection time should be >20 min.
Surface disinfection of objects
- When using ozone gas to disinfect the surface of objects, the general ozone concentration should be >60mg/m, the relative humidity >70%, and the action time is 60min~120min.
When using ozone water to disinfect the surface of an object, the ozone concentration in the water is generally required to be >10 mg/L and the action time is >60 min.
Note: The above data is from “GB28232-2020 Hygienic Requirements for Ozone Disinfectors”
03
Choice of Ozone Generator
The effect of space sterilization is related to the concentration of ozone. Therefore, when considering whether the ozone generator with a certain output is appropriate, the following formula can be used for reference: W=C×V×10-3/D
Note:
W=Ozone generator output Unit: g/h
C=Ozone dosage per unit volume Unit: mg/m3 (ozone concentration in air 1ppm=2.14mg/m3)
V=Actual ozone disinfection volume Unit: m3 [V includes V1 clean area space volume, V2 air purification system volume (can be ignored), V3 air loss volume during circulation (in the actual calculation process, V3 is equal to 1.2% of the total air volume of the circulation system)]
D=Ozone decay coefficient: 0.42
For example: If the designed ozone concentration is 1.5ppm in space and the disinfection space volume is 10000 m3, the air flow rate is 100000 m3/h
W=1.5×2.14×10-3×(10000+100000×1.2%)/0.42=85.6g/h
According to the calculation results, the ozone generator with an output of 90g/h is generally selected
04
Installation of ozone generator
Because the higher the humidity, the better the sterilization effect of ozone. This is because the cell membrane expands and becomes thinner under high humidity, and its tissue is easily destroyed by ozone. This feature is particularly suitable for the high-humidity environment commonly found in the food industry. However, some companies will place ozone generators indoors, which poses a safety hazard, because in a high-humidity environment, ozone will corrode some parts of the ozone generator itself, shorten the life of the equipment, and may also cause short circuits, failures, and even fires. Therefore, it is recommended that general ozone generators be installed outdoors and piped indoors.
05
Comparison data of disinfection and sterilization effects of ozone water and traditional methods
a. The sterilization effect of sterilizing water on the surface of objects
b. Spraying shrimp and other fish with ozone water for 5 minutes, the sensory evaluation showed that it had no effect on color, flavor and other qualities
c. Spraying shredded mustard tuber, radish slices and cucumber slices for 2 minutes, the total number of bacteria in products with different treatment methods cfu/g
06
Scope of ozone application in food enterprises
Since its discovery in 1785, ozone has been widely used as a gas disinfectant in food processing, transportation, storage, tap water production and other fields, because it can not only disinfect and sterilize space, but also act on the surface and interior of objects. In recent years, due to people’s in-depth understanding of ozone utilization technology, ozone sterilization has been increasingly valued in the food industry, and its scope of application has become wider and wider. For example, it can be used for cold storage disinfection; sterilization and purification of air in production workshops; processing, storage and mildew prevention and preservation of vegetables and fruits; sterilization and quality preservation of mineral water, as well as disinfection of production water, production tool containers, packaging materials, etc.; it helps food production enterprises pass the GMP and HACCP system certification of the food industry. As shown in Table 2, in Japan, the United States and other countries, ozone sterilization has been widely used in various aspects of food processing.
Fields of ozone application in food enterprises
07
Precautions for the use of ozone
The “Industrial Hygiene Standard” formulated by the Ministry of Health of my country in 1979 stipulates that the safety standard for ozone is 0.15ppm; the US standard stipulates that personnel can work for 8 hours at a concentration of 0.1ppm. The concentration that causes a certain reaction in personnel is 0.5-1ppm, and the allowed contact time is 1.5 hours. After a long time, they will feel dry mouth and other discomfort. Concentrations of 1-4ppm will cause coughing in personnel, and the allowed contact time is 1 hour. Concentrations of 4-10ppm will cause strong coughing, and the allowed contact time is 20 minutes. Therefore, production personnel must leave the site when ozone space is disinfected. After the disinfection is completed, the amount of ozone generation can be reduced, and low-concentration ozone that meets national health standards can be used to continue to keep the air in the production workshop clean.
Table 1 Impact of ozone exposure on human safety
Table 2 Benchmark limit values of allowable ozone concentrations
From the perspective of food safety, since the concentration of ozone sterilization is very low and it is easy to decompose, there is no residual pollution on the surface of food, so it will not have an adverse effect on food quality.
