Nov. 12, 2003

Purification by Ozonation

Purification by Ozonation: The Effects of Ozonation on Ascorbic Acid and Bacteria Colonies in Unpasteurized Apple Cider
Elena Ovaitt, 14, Weston, Mo.
Third Place, Discovery Channel Young Scientist Challenge, 2003

Project background: Elena learned that pasteurization destroys 33 to 55 percent of ascorbic acid (vitamin C) in foods and beverages such as apple cider. The company in her town that makes evaporative cooling towers uses ozone, a gas also known as triatomic oxygen, to purify water. Elena wanted to determine whether ozone would affect the amount of ascorbic acid as well as the number of bacteria colonies in unpasteurized apple cider.

Tactics and results: Elena obtained apple cider from a local apple orchard and worked with scientists at the cooling tower company to ozonate it. Elena applied three different amounts of ozone to the unpasteurized cider and then calculated the amount of ascorbic acid and the number of bacteria colonies that remained. Elena found that when compared to the control (no ozone), ozone applications of 5.2 and 7.9 grams/meter³ did reduce the amount of ascorbic acid, but only by a small amount (0.1 percent). Additionally, she discovered that some bacteria colonies did survive even the highest ozone level she used.

Elena concluded that ozone could be a viable alternative to pasteurization if a higher concentration of ozone were used. Because many foods lose ascorbic acid when pasteurized, ozonation could be used to purify these foods without destroying a lot of ascorbic acid.

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