What is the recommended range for magnesium ions in brewing water?

The recommended range for magnesium ions in brewing water is indeed 5-40 ppm. This level is significant for various aspects of brewing, particularly affecting yeast health and fermentation. Magnesium acts as a cofactor for enzymes involved in yeast metabolism, which enhances fermentation efficiency and contributes to the production of various flavor compounds, including certain esters and phenols.

Additionally, magnesium contributes to water hardness, which can influence the brewing processes and flavor profile of the final beer. Maintaining magnesium within the 5-40 ppm range ensures that it supports yeast activity without overwhelming the beer with excessive mineral character, which can lead to off-flavors or an imbalanced profile.

The other ranges either fall below or above the optimal levels, potentially leading to deficiencies or excesses that could negatively impact brewing performance and the quality of the finished beer.