Ascorbic acid, also known as vitamin C, is a common ingredient used in brewing to prevent oxidation.
During the brewing process, oxygen can be introduced to the wort or beer, which can cause a number of problems such as off-flavours, loss of colour, and reduced shelf life. Ascorbic acid can help to prevent these issues by acting as an antioxidant. It is used to scavenge oxygen and prevent oxidation from occurring.
Ascorbic acid is often added to the beer at the end of the brewing process, just before packaging. It can also be added to the wort before fermentation. The amount of ascorbic acid used can vary depending on the type of beer and the desired level of antioxidant protection.
It's important to note that ascorbic acid is not a substitute for good brewing practices, such as proper sanitation, and it should be used in conjunction with other methods to prevent oxidation.