Deaerated Water. Naturally occurring water contains a high concentration of oxygen (up to 10–12 ppm dissolved oxygen), and as oxygen is detrimental to the flavor stability of beer, any water that comes into contact with fermented beer should be “deaerated,” or more precisely, deoxygenated.
In the brewing process deaerated water is preferred, if not required, for the following uses:
The methods used for deaerating water vary from very simple to quite complicated and expensive. The simplest is boiling the water, as oxygen has very low solubility in hot water. “Scrubbing” of the water with oxygen-free CO2 or nitrogen is another method, and finally applying a vacuum to water trickling over a large surface (often in a hollow tube filled with small “fillers”) can also be applied. These processes may be repeated or combined to achieve the specified oxygen content required, often 0.01 ppm or lower.