Why is acidity adjusted before yeast is added to a fermentation mixture?

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distilled spirit The fermentation and distillation process for producing whiskey. The production of whiskey begins with grinding grain into a meal, which is cooked. Malt is introduced to the meal, which results in mash that is cooled and pumped into a fermenter, where yeast is added. The fermented mixture is heated in a still, where the heat vaporizes the alcohol. The alcohol vapours are caught, cooled, condensed, and drawn off as clean, new whiskey. This liquid is stored in a cistern room, and water is added to lower the proof (absolute alcohol content) before the whiskey is placed in new charred oak barrels for aging and later bottling.

In the production of distilled spirits, acidity is adjusted before adding yeast because yeast functions most effectively in a slightly acidic medium.1

By checking and adjusting the pH value of the grain mash, fruit juice, or molasses mixture, producers ensure the environment is optimal for the yeast enzymes to convert simple sugars into ethyl alcohol. If the natural acidity of the mixture is insufficient, acid or acid-bearing materials are added to reach the necessary levels before the yeast is introduced. This preparation is a critical step in ensuring the fermentation process proceeds efficiently to produce the desired alcohol concentration.1