RTD tea (ready-to-drink tea) processing lines need to control two important parts of production: extraction and oxidation. The extraction section needs close control of brewing time and temperature, since both can change the balance of bitterness, astringency, and tea aroma. Tea extraction uses RO water to keep calcium, magnesium, and iron at low levels, since these minerals can react with compounds in the tea and affect the appearance of the extract. Tea extract can oxidize when it stays in contact with air, and that can change both its color and flavor. In order to reduce prolonged exposure of the tea to the air, the crushing, extraction, and blending sections of the tea beverage processing line are kept closed, while vacuum deaeration removes part of the air from the tea extract before the next stage.