Why is alkalinity not desirable for brewing water chemistry?

The reason alkalinity is not desirable for brewing water chemistry primarily relates to its effect on the pH of the mash. High levels of alkalinity can raise the pH of the mash, which can lead to several undesirable outcomes in the brewing process. Specifically, a higher mash pH can inhibit enzyme activity necessary for converting starches into fermentable sugars, which impacts the efficiency of the mashing process. Optimal mash pH is typically around 5.2 to 5.5. If the pH rises significantly above this range due to excess alkalinity, it can result in poor extraction of flavors and colors from the grain, leading to an unbalanced and potentially harsh beer flavor profile.

While other factors related to yeast health and fermentation dynamics could potentially be affected by water chemistry, those do not directly connect as clearly to alkalinity as pH does. Alkalinity itself does not innately speed up fermentation or lower yeast health in a direct manner, and while managing water chemistry can incur costs, this is typically not the primary reason brewers work to manage their water's alkalinity.