Milling Grains For Beer

The transition from extracts to All Grain brewing is a natural process of evolution for any home brewer who approaches the matter not only from the practical, rational side, where beer is only a product of consumption but also with a dash of creativity, a subtle understanding of the processes and the influence of each individual factor on the characteristics of the beverage. And often, when you take that important step toward “All Grain”, you suddenly realize that you can save a lot of money if you buy the malt you use most at once by the bag, not by the kilo every time you plan to brew another one. 

Plus, it’s also a matter of convenience. But when you buy malt in large batches, you are faced with another problem – you have to grind it yourself because you cannot store malt already ground in the store for a long time, it oxidizes. This material is devoted to this important technological process.

Criteria and principles of good milling

Malt milling is an important technological operation that has a great influence on the further processes of malt preparation, in particular on the duration of saccharification, the filtration of the malt from the grain, and, of course, on the yield of the extract. The main objective of malt crushing is the complete destruction of the floury body of the grain, called the endosperm, which allows the water and the enzymes transferred into it during saccharification to interact more fully with the starch and other extract substances contained in the body of the germinated grain. Of course, not everything is as simple as it may seem at first sight.

A good malt grind completely destroys the endosperm of the grain into small pieces, while preserving the husk (the dense shell of the grain) with minimal damage. The destruction of the endosperm allows diastatic enzymes to access the starches and convert them into soluble sugars during the mashing process. The floury part of the grain, which mainly contains starch (carbohydrates) and protein (nitrogenous substances), must be crushed as finely as possible so that the maximum amount of extractive substances can be extracted from it during the saccharification process. At the same time the husks which have retained their integrity as a result of the milling process serve as a natural filtering layer when the saccharified must is discharged into the fermenter. In addition, damaged hulls, which mainly consist of cellulose and organic and inorganic substances deposited in them, can greatly impair the aroma and taste of the beer (especially due to excessive extraction of tannins, which make the beer tart).

During malting, the grain of barley and any other cereal crop is not loosened evenly, so the endosperm structure of malt grain is different. In the germinal part, closer to the base, the structure of the endosperm is looser and easily crushed, but the tips of the grain, which are usually not subjected to fermentation, are quite problematic to crush. That is why crushed malt always consists of four main fractions: the husk itself, coarse grain, fine grain, and flour. With husks, it is clear: the less damage, the better. Coarse grains, which are usually the tips of the grain, saccharify slowly. Fine coarse grains and flour lend themselves best to extraction. But it should be understood that a large amount of flour in the mash will lead to clogging of the filtration system, even if the filtration layer of husks is dense enough. That is why you should always look for a compromise between grinding fine enough for a higher degree of extraction and keeping large enough fractions for a more comfortable filtering of the mash. Be that as it may, malt milling always starts with the mill.

Choosing a malt mill

Brewers mainly use two main types of mills for grinding malt at home: Corona (also known as Victoria) grist mills and roller mills.

Corona roller mill

The Corona is a manual roller mill, in which malt is ground by the friction of the grains between two panels of metal, the millstones. A similar principle of crushing is implemented in commercial coffee grinders. The screw, which conveys the grain to the grindstone, as well as the grindstone itself, is set in motion by a rotating handle. A drill or a screwdriver can be used instead of the handle with some simple manipulation, but without a large grain hopper, this seems pointless. The advantage of the malt mill is only one – it is cheap.

The disadvantages are many and obvious: together with the floury part of the malt grain the husk is also ground, which, as we found out, has a negative impact on the following technological processes of beer wort production after grinding. However, if you set the right gap, from 0.8 mm to 1 mm, you can achieve good milling with an acceptable grinding of husks. A small hopper, where you can fill only about 1 kg of malt, also can not be called a strong side of millstones.

Roller Mill

This type of mill is a construction of one, two, or three cylindrical rollers, set in parallel and driven by hand or by electric devices (drills, screwdrivers, etc.). Crushing is done by pushing the malt grains between the rollers. The rollers themselves can be smooth or grooved, which has some influence on the speed and quality of milling. By forcing the grain through rather than tearing it between the grinders, the husks are damaged as little as possible, while the endosperm is ground as much as possible, depending on the space set between the rollers.

The fine adjustment of the gap (to a hundredth of a millimeter), the capacious hopper, and the enormous grinding speed when a drill is connected make roller mills preferable for home use. 2-roll mills have been the most common over the years, but the more expensive 3-roll designs usually provide a better grind.

General recommendations for selecting and operating a malt mill

Do not believe anyone who advocates a coffee grinder, blender or food processor as an alternative to an expensive mill. None of the household devices can provide a good malt, the main features of which were described in the previous chapter. This is clearly demonstrated in the photo of malt milled in a food processor, which, by and large, does not crush the malt, but chops it with rotating knives.

The result: a lot of unshredded grain, not at all suitable for the filter layer. You can be sure that a blender or coffee grinder will give the same result.

Setting up a malt mill

Adjusting the malt mill comes down to setting the “right” gap between the grindstones or rollers. Advanced brewers use special calibration probes (dipstick) for this, which can be used to make fairly accurate measurements across the entire plane of the gap. Unfortunately, there is no universal clearance setting. Millers from different manufacturers can have completely different roller configurations – some are smooth, some are fluted, some are knurled, and some are larger or smaller in diameter. Any variation in the roller configuration of a mill will result in a different grinding degree with the same settings, so the grinding gap has to be set individually for each piece of equipment (for an average 2-roller mill the optimal gap is between 0,86 mm and 0,91 mm). In the absence of feeler gauges, the adjustment has to be done empirically by grinding small batches of grain.

In factories for measuring the grinding also use test sieves, sifting samples through which you can determine the percentage of certain fractions in the grinding.

Six sieves with a mesh size of 2 mm (#10), 1.4 mm (#14), 1 mm (#18), 0.6 mm (#30), 0.25 mm (#60), and 0.15 mm (#100) are used for precise measurements. The ground malt is placed on a pyramid of these sieves, after which it is sieved and the fractions collected on each sieve are weighed. Briess Malt & Ingredients conducted a series of studies to determine the optimal content of the various malt fractions in the mash, using #14, #30, and #60 sieves. Without going into detail, we summarize the results of the research and give you the most optimal values:

The main conclusion is that 50-55% of the #14 fraction in the milling is the optimal value. In field tests, brewing beer on the factory equipment with these milling values resulted in 91% extraction and 94 minutes of wort filtering. A coarser grind (78% fraction #14) gave only 85% of extraction, while the time of filtering from the mash was not reduced (96 minutes). A finer grind (25% of the #14 fraction) gave 92% extraction but increased the filtering time to 143 minutes.

Can these conclusions be applied in practice at home? A set of laboratory sieves is not cheap, but all of them are unnecessary. In fact, you can get by with only sieve #14, that is, a sieve with a mesh of 1.4 mm. Practice shows that if the amount of #14 fraction stays within 50-60%, the rest of the fractions will be fine, and this kind of grinding is almost guaranteed to provide both high efficiency of saccharification and fast enough filtration. It should be noted that all of the above applies only to 2-roll grain mills.

Wet malt milling

The latest trend in breweries is to wet malt before it is milled. After wetting, the husk becomes elastic and is less subject to crushing. The idea is to squeeze the endosperm from the shell of the grain like a banana from its peel, which allows the floury part of the malted grain to be completely crushed at a smaller roller gap while leaving the husks intact. Obviously, this can only be done when the husks are soft and supple. Moistening the malt before crushing it has become somewhat popular at the homebrewing level as well. The main rule here is to increase the moisture content of the grain by no more than 2% of the original value, because malt absorbs moisture very actively, which can lead to poor grinding of the endosperm and the stickiness of the flour.

At home, crushing the malt is as follows: the top of the grain is sprayed from a sprayer with a small amount of water (not more than 100 ml per 5 kg of malt), and then the entire malt is turned to absorb the remaining moisture from the husk over the entire volume of the malt. It is better to do this procedure in stages, sprinkling only part of the water at a time. If you overdo it, the floury part of the grain will also absorb some moisture, becoming sticky and sticking to the rollers of the mill. If this happens, you should run dry malt through the rollers to clean them. Hot water can be used for moistening, which is thought to be absorbed by the husks more quickly. As mentioned earlier, wetting will set the gap between the rollers much smaller, which will ultimately produce more fines for more efficient extraction, but still keep the husks in pristine condition for quick wort filtration from the grain.

How will this affect milling? The tests showed that with the same roller spacing, wet malt after milling leaves in sieve #14 about the same amount of coarse grain as milled dry malt, but much less weight because only nearly undamaged hulls and a small amount of floury part of the grain remain coarse. At the same time, the amount of fine coarseness and flour increases significantly (the amount of coarse malt flour can be twice as much when malt is moistened). The photo below shows samples of milling dry and wet malt on a 2-roll mill with a gap of 0.48 mm (left – crushed dry malt, right – wet, below – the same milling with enlargement). The difference is obvious!

Wheat malt can also be moistened in this way before milling. Despite the absence of husks, wheat malt still has a kind of shell around the endosperm, which can be preserved during the crushing process by moistening it. This will make it possible to comfortably brew beer with a high wheat malt content in the mash without using auxiliary ingredients such as rice. The photo below shows samples of milling dry and wet wheat malt on a 2-roll mill with a gap of 0.41 mm (left crushed dry malt, right – wet, bottom – the same milling with enlargement).

FAQs

Conclusion

First of all, you have to do what is best for your brewing system. For example, when mashing malt “in the bag” it is better to grind as finely as possible so that the extractions at the end result is 80% or more. For a RIMS or HERMS brewing system, you should dig towards a coarser grind to ensure good wort circulation and further filtration. You should also keep in mind the chemistry of the water and adjust the pH of the wort accordingly. The size of the mash directly affects the speed of hydration and dissolution of minerals and enzymes, so expect the mash pH to take a bit longer to stabilize with coarser mash (experience has shown that wort pH stabilization with coarse malt takes about 25-30 minutes, while with finer mash it takes 5-10 minutes to know stable pH). Brewing is a creative process and it’s important to never forget that!