Beer line cleaner goes green because it contains a chemical called sodium metabisulfite. This chemical reacts with the organic compounds present in beer, particularly proteins and tannins, causing a color change.
When beer line cleaner is used, it is typically flushed through the beer lines to remove any residue, bacteria, and other contaminants that may affect the taste and quality of the beer. The purple color of the cleaner is simply a visual indicator, making it easier to see that the cleaning agent is being used in the beer lines.
As the beer line cleaner comes into contact with beer residue and organic compounds, the sodium metabisulfite in the cleaner reacts with these substances. This reaction leads to a chemical change, resulting in a green or yellow color. The exact color may vary depending on the specific cleaner being used.
The purpose of the color change is to show that the cleaning agent is actively working to break down and remove the organic compounds in the beer lines. It serves as an indication that the cleaner is being used effectively to clean the beer lines and not just flowing through without any impact.
It's worth noting that the color change is not instantaneous. It may take some time for the reaction to occur and for the cleaner to turn green or yellow. This is why it is important to follow the recommended cleaning instructions and allow sufficient contact time for the cleaner to work effectively.
Personally, as a brewer, I have used purple beer line cleaners numerous times to clean the beer lines in my brewery. Seeing the cleaner turn green or yellow gives me confidence that it is effectively breaking down any beer residue and contaminants, ensuring that the lines are thoroughly cleaned.
The green color of beer line cleaner is a result of a chemical reaction between the sodium metabisulfite in the cleaner and the organic compounds present in beer. This color change serves as a visual indicator that the cleaner is actively working to clean the beer lines and remove any residue or contaminants.