Milling Grain: Tips from the Pros

When you are brewing with grains, everything starts with the grain you buy. Whether you’re adding a few pounds to an extract batch or brewing ten all-grain gallons, lousy grain makes lousy beer and great grain makes great beer. But how the grain is milled is also an important factor. Bad milling can create problems during the brewing process and result in beers with off-flavors. Milling grain isn’t rocket science, but it involves precision. The objective is to mill the malt as finely as possible, but not so fine as to cause a stuck mash or compromise wort clarity. Finding the right mill setting for your malts can involve some tinkering and adjusting of your mill. To make the job a bit easier, we offer helpful tips from this month’s lineup of benevolent pros.

Brewer: Marc Worona of Stoudt Brewery in Adamstown, Pennsylvania. Marc took the microbiology course at Siebel. He has been the brewer at Stoudt’s for more than 5 years.

A lot of specialty grains are six-row, so the kernel is going to be smaller than the two-row pale base malts. This means that you can’t use the same mill opening for your base and specialty malts. You’ll need to tighten the mill for your specialty malts.

We use all two-row malts, but they are still quite different in size, so we end up setting the mill by visual inspection. We inspect to avoid an excess of grains that aren’t crushed at all by the mill. Only about 2 percent should go through the mill uncrushed.

Our goal is to crush the grains as much as possible without making the grist too fine. A “too-fine” grist is powdery, with shredded husks and destroyed grains. The best scenario is to have grains that have been cracked open with the husk separated from the grain, to form a filter bed during the sparge. There are many variations between a “coarse” and a “fine” grind and tinkering with the mill settings will let the homebrewers find what works best for them.

With more problematic grains like wheat malt, I still crush them thoroughly. They can turn gooey in the mash and create a stuck mash, but by adding rice hulls to the mash you can create a filter bed. Rice hulls serve as good filters. Use them at a rate of about 5 percent of the malt bill, adding them evenly as you put the malt into the mash tun.

Brewer: Sean Larkin of Trinity Brewhouse in Providence, Rhode Island. After a one-year internship at Trinity, he became head brewer in 1994.

We were originally buying pre-milled grain from our supplier, but made the decision that it would be better to mill the grain ourselves. After we got the grain and mill, we had to adjust and readjust the mill until we got it set where we liked it. We have settled on a coarse grind. Instead of a 100 percent crush, which means it’s fine and powdery, we target a 65 percent crush. This means some whole grains are going to slip through the mill, especially since we don’t have screens to catch the different-size grains. But if some whole grains do slip through, we figure our settings are right and we aren’t cracking the smallest grains that are going through the mill.

The first rule of milling is to not pulverize the grain. Pulverizing your grains can lead to stuck mashes. When you pulverize the grain, you destroy the embryo and the husk. This leaves you without a filter. You also end up with a bunch of flour that will turn to paste and collect on the bottom of the mash tun, and block the flow of sparge water.

The second rule is to barely crush specialty malts, taking care only to crack open the grains. These are roasted at higher temperatures, so they’ll tend to pulverize during milling if you aren’t careful. Keep your mill settings wide enough to just break them open. Also, it’s best to add them to the mash toward the end of the mash-in to keep them on the top of the mash.

Brewer: Matt Cole of Rocky River Brewing Company in Rocky River, Ohio. Matt completed the Siebel Short Course as well as the University of Sunderland (England) Short Course before joining the Rocky River Brewing Company in 1998.

We use pre-milled grain for our brewery because we are constrained by some local laws. (We can’t have a bulk grain silo.) This actually works out quite well for us and it’s also an option for homebrewers. Many homebrew shops sell pre-milled grain or can order some. Also, they might mill the grain for you at the shop. I like using pre-milled grains for several reasons. I find that extraction efficiency is consistently good with the pre-milled grain, and protein coagulation also tends to go down some.

The only potential downside to pre-milled grain is its shelf life, but even that doesn’t impact us too much. We tend to use any grain that we get within three months of the milling date. So far I haven’t experienced any negative effects from storing my grain that long. Perhaps six months would be the longest I would store milled grain, but a few months is definitely okay.

We do, however, mill our specialty malts and we do this in our two-roller mill. I don’t do any fancy measurements, like making sure the rollers are X millimeters apart. I just eye the setting, make sure I like where it is, and then lock it up so the mill setting will not budge.

My ultimate goal is to just barely crack open the grains. In fact, I would far prefer to undermill my grains rather than overmill, because pulverizing the grains can tend to extract tannins and other things that might cause astringency. There are newer commercial methods of milling and wort separation that allow the use of very fine milling without increasing astringency, but a homebrewer should take care not to mill too finely.

When it comes to overmilling, you have to take care in the case of any highly modified grains. This might be Munich malts on the low end or caramel 120 on the high end. These types of grains tend to shatter, so when milling these, it’s important that you adjust your mill settings to be a bit less aggressive than you would with pale malt.