Acid Malt is a pale malt that has been subjected to a lactic acid fermentation after kilning and a second finishing drying cycle. The lactic-acid bacteria reside naturally in the malt. The purpose of acid malt is to reduce the pH value of the mash. Proper mash pH (5.4 to 5.6) helps assure the enzymatic performance on which the brewer relies to break down gums, proteins, and starches. It also leads to proper wort pH, which affects yeast performance during fermentation and the final flavour profile of the resulting beer.
Every 1% of acidulated malt (by weight) of the total grain bill reduces the mash-pH by 0.1 point. In highly alkaline mashes, acidulated malt can make up as much as 10% of the grain bill.