In a discussion I recently about decoction, the topic of under-modified malt came up. Decoction mashing is typically associated with under-modified malt, as it helps break up the not yet fully dissolved endosperm of the malt with the help of boiling parts of the mash, while at the same time, the enzymes themselves have been dissolved in the thin mash.
Maybe let’s step back a bit, and talk about malt modification. To produce malt, grains are germinated by soaking them in water and giving them time to sprout. What happens is that the grain starts growing, all kinds of enzymes are produced, and the internal structures of the hard barley grain are modified to make it softer. Protein within that grain becomes soluble, and eventually, the grain starts to grow to become a new plant. Of course, that’s not what we what, the brewer wants to have the starch and the enzymes, so these are locked in by drying the so-called green malt. In order to determine how far this modification has progressed, the ratio of soluble proteins compared to the total amount of proteins is measured. You will find this in brewing literature als SNR (soluble nitrogen ratio) or Kolbach index, and it’s a percentage. A Kolbach index of less than 35 is considered to be poorly modified or undermodified malt, 35 to about 40 is considered well-modified, 41 to 45 is very well-modified, and over 45 is considered to be over-modified.
While decoction mashing is a remedy to deal with under-modified malt, some homebrewers even turn this around and say that under-modified malt would even be necessary for a decoction mash. In my opinion, using under-modified malt is not a necessity, and a decoction mash works equally well with well-modified malt, it just is not strictly necessary. If you want to do a decoction mash, use whatever malt you prefer, and don’t worry about it.
Now, if I as a homebrewer wanted to use an under-modified malt, which one would I buy? You sometimes read rumours that the Weyermann floor-malted Bohemian malt is poorly modified, but there’s not really much substantial information around. So I went out and tried to get some more detailed specifications on the base malts of two well-known German maltings, Weyermann and Bestmalz to see whether there’s any poorly modified base malt in their portfolio.
When I went through Weyermann’s specs to get the Kolbach index, I was actually genuinely surprised: all of their base malts are well-modified, some of them even specified to be potentially over-modified. These are the ones I had a look at:
- Barke Pilsner malt: 36-41.5
- Barke Vienna malt: 37-44.5
- Barke Munich malt: 38-45
- Pilsner malt: 36-42.5
- Vienna malt: 37-45.5
- Munich malt type 1: 37-46
- Munich malt type 2: 38-47
- Pale Ale malt: 37-43
- Bohemian Pilsner malt: 38-42
Every single malt was well-modified. What about Bestmalz? Same thing, really:
- Heidelberg malt: 36-43
- Pilsner malt: 36-45
- Vienna malt: 37-45
- Munich malt: 36-47
- Munich (dark) malt: up to 47
- Pale Ale malt: 36-45
What’s noticeable is that with both maltings, the darker kilned malts (Vienna malt, Munich malt) have a tendency to be specified to be more modified than the less kilned, paler malts like Pilsner and Pale Ale malt.
So, if I really wanted to brew with a properly under-modified malt, what options do I have? Not many. There is one product though that falls well into the under-modified range: chit malt, or as it’s called in German, Spitzmalz.
Chit malt is produced by kilning green malt that has barely sprouted. There is only a tiny tip poking out from the malt, indicating that modification has not gone very far yet. Because of this, chit malt is Germany’s loop hole around the prohibition of using unmalted grains according to modern beer legislation: because it’s technically malt, it can be used, but still has many of the properties of unmalted grains. Sometimes, you will also read about the use of chit malt being recommended to compensate for over-modified malts.
And that’s how you can approximate an under-modified malt for which you need to use a decoction mash: by mixing well-modified (but not over-modified) with a relatively large portion of just chit malt. Some sources on the internet say that you can theoretically use up to 40% of chit malt, and will be able to produce a reasonably good quality wort by employing a decoction mash. Papers on the TU Munich website suggest that even a 100% chit malt mash is possible.
Specification about chit malts are a bit sparse, especially when it comes to the Kolbach index. Bestmalz describes theirs as “up to 34”, but the lower threshold is not mentioned at all, so it can be extremely under-modified at worst. Weyermann stopped producing chit malt a few years ago due to lack of demand, and recommends CaraPils as an alternative if your intention to use chit malt was a better foam stability.
Given this information, I would say the best bet for homebrewers is to mix normal base malts with chit malt in amounts of 10 to 40%. Personally, I am not super keen on actually trying it, but if you insists on doing a decoction mash using under-modified malt, go for chit malt.