During the past 20 years, vegetable and fruit consumption in the US had increased, causing more people to become ill due to chemical substances in food and waste water. Presently, the number of produce associated of microorganisms that cause food-borne illness cannot be controlled and significantly increases. Deterioration of vegetables and fruits, accounting for 30%, occurred both in the industrial sector and transport, is mostly caused by microorganisms from post-harvest to consumption.

     Using chorine for cleaning and pasteurizing is convenient and practical for industry. It also can control and reduce count of disease caused microorganisms that are found in vegetables and fruits. However, according to a study, the quantity of chorine used to inhibit bacterial growth in vegetables and fruits cannot be clearly identified.

     The Organization of Environment and Health showed the relationship between cleaning agent and its residues, such as Trihalomental, and other chemical residues in waste water which was discharged from the industrial production sector into natural resources. Such a relationship indicates the possibility of applying chorine as a cleaning agent and pasteurizer in the future. Chorine is a chemical group that has been used to kill and control plant insects in the production process for vegetables and fruits. With the current production technology, pesticide residues on the surfaces of vegetables and fruits cannot be eradicated, directly affecting consumers' health and polluting environment as well. Therefore, several countries have paid attention to cleaning agents, pasteurizing agents, and other chemical substances which have been used in the production process in the food industry.

     From a research study, it was shown that ozone could replace chorine. In 1997, ozone was accepted by GRAS that it was safe for use and did not leave any chemical residues. In addition, EPRI allows the industry to use ozone. In responding to this matter, the industrial sector is interested in the methodology and detailed applications of ozone as a cleaning and pasteurizing agent.

Why Ozone?

     Ozone is a strong oxidizer and better than chorine 1.5 times. It also can destroy microorganisms that cause food-borne illness better than chorine does. Ozone can kill microorganisms, such as Ecoli, Listeria, and microorganisms that cause other diseases, and has no residues. Ozone has a high molecular power and a half life in water at a room temperature for 20 minutes and can easily break down to oxygen without leaving residues when used in food products. Furthermore, ozone has been applied to turn used water to clean water which can be reused to wash vegetables and fruits in the production process. The water used for cleaning has gone through the combination process with ozone and the filtering process. As a result, the water is free of bacteria, color, and other contaminants. Moreover, the used water can then be recycled to reduce water consumption. The ozone system is unlike the use of chorine in a way that used water will be discharged with ozone, leaving no residues and causing no pollution to the environment and underground water system. Ozone can get rid of pesticides and chemical residues e.g. residues from chorine etc. Gaseous ozone is a good cleaning, pasteurizing, and fumigation agent. In addition, ozone can be used to clean a food storage during transportation to prevent bacteria, mold and yeast clinging on food surfaces, and to control flies on the food surface. Ozone can eliminate undesirable flavor caused by bacteria and athelene gas to delay the ripeness of fruits.

     During the past 10 years, ozone has been accepted as a highly efficient cleaning and pasteurizing agent to extend the shelf life of food products, and widely used in the European countries to improve water and water used in the food production process. In the US , ozone has been employed in the production process for drinking water in tightly closed containers, and in the food production process as well. According to a study, it was found that ozone was extremely useful for the food industry in a way that it was used to clean and kill germs and efficiently control microorganisms which caused food-borne illness. A study done in 1840 revealed that molecule of ozone consisted of 3 atoms of oxygen.

Attributions of Ozone

• Be able to dissolve in water better than in gas. Dissolving will increase while temperature decreases.
• Ozone is efficient in killing microorganisms by oxidizing with cell walls of microorganisms.
• Ozone is able to break down itself without leaving any residues.
• Ozone, an oxidizer, is stronger and more efficient than chorine in destroying microorganisms and other germs.
• Ozone is borne from ultraviolet ray from the sun and purposely produced for commercial use from UV ray at the frequency of 185 nm or corona discharge. In general, corona discharge is found at the 1-3% w/w air concentration and 2-12% w/w oxygen concentration.

Using Ozone to Extend Shelf Life of Vegetables and Fruits

     Ozone can be utilized to keep vegetables and fruits stored in a chilled room. It prevents mold and bacteria in the air from growing on the products at a low concentration of ozone. It also can destroy microorganisms on the food surface; as a result, the shelf life of produces is extended. In 1933, a study was done on use of ozone to store numerous kinds of vegetables and fruits e.g. apples, potatoes, tomatoes, strawberries, broccoli, pears, canberries, oranges, peaches, grapes, corns, and soybeans. In 1955, Barth etal did a study on utilization of ozone to store blackberries by starting the studying process from post-harvest to storage. The fruits were stored at the temperature of 2 ? C, 0.3 ppm concentration of ozone. It was found that the storing period could be expanded by 20% without any blemish on fruits and change in color after being stored for 12 days.

     Storing vegetables and fruits by ozone is another good method of extending shelf life of strawberries because they get rotten easily in a wet condition. If using ozone to store strawberries, raspberries, currants, and grapes can increase their shelf life 2 times with the ozone concentration of 2-3 ppm and by releasing ozone few hours a day.

     In 1968, Noton et. al discovered that use of a relatively low temperature together with ozone could very well control the growth of mold. In 1953, Kuprianoff found that the shelf life of apples could be prolonged further several weeks by applying ozone for the amount of 2-3 cm3 / m3 and releasing it for approximately 1-2 hours/day. But, if using ozone 10 cm3 / m3 will give a detrimental effect on apples. Baranovskaya et. al (1979) found that the shelf life of potatoes, stored at the temperature of 6-14 ? C, 93-97% humidity, and ozone concentration of 3 ppm, could be extended to another 6 months without damaging the quality of potatoes. However, the important thing is ozone can be employed in a chilled room where vegetables and fruits are stored to prevent ripening. Ozone will decrease athelene gas released by vegetables and fruits, resulting in the delay of ripeness of vegetables and fruits.

Source: Food Institute Periodical