Conditioned Milling
The basic process of brewing beer is the same whether beer is brewed commercially or at home. However, differences in scale and equipment have lead to numerous small differences between commercial and home brewing. In homebrewing, malt is almost always crushed dry, using a two-roller mill. In larger commercial breweries, four, five or six-roller mills may be employed and sometimes the malt is wetted before it is milled.
In an older form of wet milling, little practiced in the US, the malt was sprayed with 86–122 °F (30–50 °C) water for 15–30 minutes prior to milling. During this process, the water content of the malt increased to about 30%. The wet grain was then put through a two-roller mill with a narrow gap (compared to that used for dry milling). The wet husks were split and the pasty interior of the grain squeezed out.
Wet milling reduced the possibility of a grain dust explosion in the brewery. In addition, the larger husk pieces made for a more porous grain bed, which allowed brewers to increase their lautering speed and have fewer husk pieces in the run off wort. If the lautering speed was not increased too much, wet milling resulted in higher extraction efficiency. Likewise, because the husks were left mostly intact, tannin extraction was decreased.
This form of wet milling can’t be done at home — not easily, at least — but there are variations on wet milling that can. In these methods, the malt is exposed to steam or hot water for a short period of time, just long enough for the husks to absorb some moisture.
In conditioned dry milling, malt is exposed to steam or sprayed with 86–95 °F (30–35 °C) water for 1–2 minutes prior to milling. Due to this treatment, the moisture content of the husks rises by a couple percentage points, but the moisture level of the interior of the grain remains basically unchanged. In steep conditioning, the malt is sprayed with water at 140–158 °F (60–70 °C) for 50–60 seconds prior to milling. The hotter water results in faster water uptake by the husks, which reach up to 22% water by the end of the steep.
If you are an advanced all-grain brewer who has had problems with small husk particles, astringency or slow runoff when using finely-crushed malt, you may want to experiment with conditioning your malt. There are a couple ways you can approach this.
Conditioning with Steam
To wet your malt with steam, you’ll need a large steeping bag and a heatable lauter tun with a false bottom. Add water to your lauter tun until it is just below the level of the false bottom and bring it to a strong boil. Place your (uncrushed) malt in the steeping bag and lower the bag into the lauter tun. Over the next minute or two, steam from the boiling water will be forced up through the grains. If you like, you can take your mash paddle and stir the malt a couple times while it is being steamed. This isn’t necessary, however. Put a lid on the vessel when you are not stirring. After the steaming period, lift the bag out, stir the malt briefly and then begin milling.
Conditioning with Hot Water
To wet your malt with hot water, you will need essentially the same set-up as with steam conditioning, but your lauter tun does not need to be heatable. You will also need a way to spray or sprinkle the water over the grain. For example, heat your water to 158 °F (70 °C) and fill a watering can. Sprinkle water over the malt for 50–60 seconds. Let the excess water drain into the space below the false bottom. (Leave the valve on the vessel open.) If you have a brewing partner, he or she should stir the malt as you pour the water. When you’re done, lift the bag out and stir the malt to even out the moisture. Let the malt sit for a minute or two, then crush it. The excess water can be added to your mash.
Practical Considerations
Applying too little water is greatly preferable to applying too much. In the worst case scenario with too little water, your grain will simply be dry, as it usually is. In contrast, if too much water is added, starch flour and excess water can form a sticky paste that is hard to clean and could potentially gum up your rollers.
The main idea is to wet the husks, but leave the center of the grain dry. So, be sure to mill your grain right after conditioning it, while the water is still confined to the outer layer of the kernel. If you steam or spray your malt, but delay crushing it, the water will diffuse more evenly throughout the grain. Letting the malt rest for a few minutes between conditioning and crushing is not going to lead to problems, but this isn’t something that you should do the night before and then crush in the morning.
After conditioning, your grain should not seem dry, but it shouldn’t be dripping wet, either. If some of the kernels stick together, stir the malt and let it sit for a minute or two. The grain should not be so wet that the rollers on your malt get gummed up with flour. If this does happen, small amounts of sticky flour can be removed by running some dried grain through the mill. The larger husk particle size will result in a more porous grain bed, and the same weight in malt will occupy more volume.
A malt mill is one of the larger expenditures for an all-grain brewer. As such, you may be leery of trying to condition your malt, for fear you will gum it up or rust your rollers. If you condition your malt properly, this shouldn’t be an issue. If you have any expired malt lying around, try one of the above procedures and crush a small amount of it to see how it works.
The first few times you try this technique, mill some dried malt at the same gap setting for comparison. Compare the two samples of crushed malt and look for larger husk particles in the conditioned malt. Also, take good notes during your brewday and calculate your extract efficiency. Finally, compare beers made from dry milling and wet milling. Use this information to determine if you feel conditioned milling is worth the time and effort.
