Sour mash

Well-known brands of sour mash whiskey are Jim Beam and Jack Daniel's.

The acid introduced by the sour mash controls the growth of bacteria that could taint the Bourbon.

In order to promote fast bacterial fermentation and reduce yeast activity, the mash is kept between 100–120 °F (38–49 °C).

Some beers employing sour mashing are fermented with the addition of brewing yeast but without a boil.

Other brewers prefer to boil their sour mashed beer and then ferment it with brewing yeast.