Mineral waters have been widely used since long ago because of its abundance of natural minerals useful for human life. In recent years, the variety and production of bottled mineral waters have increased rapidly due to water pollution from various causes, depletion of drinking water sources and increasing demand of human for health. An important issue in the production of bottled mineral water is to maintain the physical and chemical characteristics including hygienic safety and color and taste after bottle packaging, for a certain period of time. This encouraged some studies to analyze the microbial status of bottled mineral water and to explain the cause of microbial development and growth.
It is not microorganisms alone that affect the quality of mineral water. Mineral waters also contain unstable components such as iron, manganese and sulfur which are possible to be removed by ozone-rich gases. However, among the inorganic materials in mineral water sources, Fe2+ that fails to undergo sufficient oxidation can be oxidized to Fe3+ during storage of mineral water and become precipitates, which do not change the total iron content in mineral water, but may change the physical properties such as turbidity. Therefore, Fe2+ should be fully oxidized and deposited before the bottling of mineral water to increase the shelf life of mineral water.
Most mineral water, especially with CO2 above 400mg/L-1, has a pH below 7, which might also have a negative effect on ozone treatment of mineral water. In addition, CO2 gas, which is dissolved in mineral water, makes it difficult for other gases to dissolve in mineral water. This is because, according to Henry’s law of solubility, the amount of gas dissolved in water depends on the partial pressure of the gas dissolved in the water. Therefore, effective oxidation and deposition of Fe2+ by using ozone gas in CO2-rich mineral water requires a new method of ozone injection and injection conditions to suit the characteristics of mineral water.
Choe Un Hwa, a researcher at the Faculty of Physical Engineering, has chosen a suitable ozone injection step and proposed a new mineral water treatment method using microbubbles by considering the characteristics of mineral water with a low content of ozone but much CO2.
As a result of the treatment of bottled mineral water with ozone microbubbles, the concentration of the iron ion was reduced from 0.14 to 0.01 mg/L-1, and the shelf life increased to 360 days. During the treatment, the concentrations of K+ and Na+ almost remained unchanged, and the deposition time was reduced to one-third compared to natural oxidation.
You can find the details in her paper “REMOVAL OF DEPOSITS AND IMPROVEMENT OF SHELF LIFE IN CO2-RICH MINERAL WATER BY OZONEMICROBUBBLES” in “QUMICA NOVA” (SCI).
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