Mashing - Grain Milling

Grain Milling

The grain used for making beer must first be milled. Milling increases the surface area of the grain, making the starch more accessible, and separates the seed from the husk. Care must be taken when milling to ensure that the starch reserves are sufficiently milled without damaging the husk and providing coarse enough grits that a good filter bed can be formed during lautering.

Grains are typically dry-milled. Dry mills come in four varieties: two-, four-, five-, and six-roller mills. Hammer mills, which produce a very fine mash, are often used when mash filters are going to be employed in the Lautering process because the grain does not have to form its own filterbed. In modern plants, the grain is often conditioned with water before it is milled to make the husk more pliable, thus reducing breakage and improving lauter speed.

Two-roller mills Two-roller mills are the simplest variety, in which the grain is crushed between two rollers before it continues on to the mash tun. The spacing between these two rollers can be adjusted by the operator. Thinner spacing usually leads to better extraction, but breaks more husk and leads to a longer lauter.

Four-roller mills Four-roller mills have two sets of rollers. The grain first goes through rollers with a rather wide gap, which separates the seed from the husk without much damage to the husk, but leaves large grits. Flour is sieved out of the cracked grain, and then the coarse grist and husks are sent through the second set of rollers, which further crush the grist without damaging the crusts. There are three-roller mills, in which one of the rollers is used twice, but they are not recognized by the German brewing industry.

Five- and Six-roller mills Six-roller mills have three sets of rollers. The first roller crushes the whole kernel, and its output is divided three ways: Flour immediately is sent out the mill, grits without a husk proceed to the last roller, and husk, possibly still containing parts of the seed, go to the second set of rollers. From the second roller flour is directly output, as are husks and any possible seed still in them, and the husk-free grits are channeled into the last roller. Five-roller mills are six-roller mills in which one of the rollers performs double-duty.