MALT PRODUCTION: What makes Munich malt production unique?

by Al Korzonas (korz@xnet.com)

When the fine DeWolf-Cosyns malts reached the US, I was puzzled by the difference between their Aromatic and Biscuit malts, both of which are about 25 degrees Lovibond in colour. After some investigation, I found that the difference was that Aromatic was high-kilned, produced like Munich malt and that Biscuit was toasted malt.

In response to a series of posts on the Homebrew Digest, I have put together the following article which describes the differences in production between pale malts (such as Pale Ale and Pilsner), high-kilned malts (such as Vienna, Munich and Aromatic) and roasted malts (such as Biscuit, Victory(TM), Chocolate, Carafa(R), Black Patent and Roasted Malt). This article will center mostly on high-kilned malts and then describe the production differences between them and the other types of malt.

The Kiln

A kiln is a large "room," effectively, usually with multiple levels, which has slotted floors so that ventilation air can be blown up from below or sucked up from above. The volume and temperature of the air and the amount of recirculation can be controlled.

There are two parts to kilning: the "drying phase" and the "curing phase." The temperature of the curing phase is what distinguishes Munich (usually about 8 Lovibond) and Aromatic (25 Lovibond), but it's the drying phase that distinguishes pale malts from "high-kilned" malts like Vienna, Munich and Aromatic [DeClerck, p.182].

Drying Phase

In the kiln, there are three factors: time, temperature and ventilation. For the production of pale malts like Pale Ale and Pilsner malt, the temperature is relatively low (40-45C) and ventilation is very high. Moisture is removed rapidly and the malts are therefore dried quite quickly. Once the moisture is below 10%, the temperature can be raised. Raising the temperature earlier would result in significant enzyme loss. The low moisture protects the malt enzymes from denaturing [DeClerck, p196].

For the production of high-kilned malts like Vienna, Munich and Aromatic, the initial temperature during the drying phase is higher (about 50C). Furthermore, the ventilation is considerably lower. As a result, the moisture content of the malt only drops to about 20% in the first 24 hours [DeClerck, p.197]. Typically, high-kilned malts take about twice as long to make as pale malts [Malting and Brewing Science, p.177]. Clearly there is a significant amount of enzyme loss in the production of high- kilned malts, but this higher temperature drying is important for the production of high levels of soluble sugars and amino acids which are later utilized in the production of melanoidins via Maillard reactions and Amadori rearrangements [Malting and Brewing Science, p.105]. It's these melanoidins that give high-kilned malts their colour and characteristic aroma.

Interestingly, the temperature profile of Vienna malt kilning looks more like Pilsner rather than Munich malt (from fig.79 on page 198 of DeClerck).

Curing Phase

Pale malts typically are cured at 80 to 95C for 5 hours. Temperatures above 80C, however, are only used if the malt is not over-modified and was dried at low temperatures. Munich malt is typically cured at 105C for 5 hours [DeClerck, p.197]. Aromatic malt is typically cured at 115C [Busch, personal communication].

Crystal Malts

Crystal malts have something in common with high-kilned malts in that the ventilation is restricted during the initial period. They can be made in a kiln or in a special roasting drum. In either case, the wet (green) malt is put into the kiln or roaster from the germination tanks and the moisture is kept very high with absolutely no ventilation. Frequent water additions are sprayed to keep the moisture high. The temperature is raised to 60 to 70C for 30 to 40 minutes. Then the temperature is raised to 150C and normal ventilation is resumed for 1 to 2 hours, depending on how much caramelization is desired (i.e. depending on whether 10L crystal or 90L crystal is being made). If prepared in the kiln, further drying is necessary [DeClerck, p242].

During the initial hot, wet heat, the malt effectively converts right in the husk. Alas, all the enzymes are denatured during this period. Because the starches in the crystal malt have been converted to sugars, crystal malts do not require mashing and can be steeped in hot water for use in extract brewing.

Roasting and Toasting

With the exception of crystal, all malts are dried in the kiln and then can optionally go into the roaster. A barrel roaster is the most common type and consists of a rotating drum that's heated from below. It also has water sprayers installed which are used to douse the malt (to cool it quickly) when it is done (although I suppose it may be used to put out fires too, which I'm told are more common than the maltsters would like!).

Biscuit and Victory are often called "toasted" malts. Really the difference between these and the much darker Chocolate and Black Patent is time and (mostly) temperature. There is some disagreement between maltsters whether damp or dry malt should be used in the roasting drum [DeClerck, p.244], but most maltsters use dry malt similar to Pilsner or Pale Ale malt. In the barrel roaster they make Biscuit, Victory(tm), Chocolate, Carafa(R), Black Patent and Roasted Malt. They also start with dry barley and make Roasted Barley and Black Barley in the roaster.

Summary

So, as we can see, there is more to Munich malt production than just higher temperatures in the kiln -- at the expense of some diastatic and proteolytic power, high-kilned malts are dried in a hotter, *higher- moisture* kiln for the first 24 hours and only *then* raised to a high temperature. Biscuit, on the other hand is dried just like Pilsner or Pale Ale malt and then roasted lightly till it is 25 degrees Lovibond.

Incidentally, Aromatic malt still has enough enzymatic power to convert itself, but Biscuit has essentially no enzymes left and must therefore rely on other malts' enzymes for conversion.

Victory is a trademark of Briess Malting Co.
Carafa is a registered trademark of Mich. Weyermann GmbH.

Al Korzonas, Palos Hills, IL
korzonas@xnet.com
Author of "Homebrewing - Volumes I and II" to be published in late fall `97 and `98 respectively.