100% Oat Malt beer

Ken writes:

My mother is gluten intolerant. It is something that has developed recently and I’m not sure to what extent it affects her, but she now doesn’t eat bread and pasta etc made from wheat. Barley also contains gluten and some of the glutelin proteins do manage to survive the process through into the final beer (most protein from barley is removed during brewing at various stages). The personal angle allowed me to reflect on how gluten intolerant people are poorly served in general by commercial brewers and that may be a niche for small scale brewers. There’s one outfit in Auckland New Zealand producing only gluten free beer and they seem to be making ends meet.

I came across an article in the Journal of the Institute of Brewing on brewing with 100% malted oats.* The coeliac disease/gluten intolerance angle is given as a motivation for exploring brewing with oats because most gluten intolerant people and coeliac patients can tolerate oats. I thought it might be fun to try to brew at home with 100% oat malt.

It proved pretty challenging. Oat has more proteins, lipids and beta-glucans (endosperm cell wall polysaccharides) than barley, and all of these things are bad or problematic from a brewing perspective. Lipids can give you off flavours when they oxidise (as everything inevitably does), means the shelf-life of oat beer would be less than barley beer if the lipids are not somehow removed during brewing. Lipids can also affect foam stability negatively. Proteins can be good for foam stability, but they also can interact with polyphenols in the oat or barley husk and in the hops to form large molecules that create a visible haze in the finished beer (yes, there is such a thing as invisible haze. It makes beer appear gel-like). And beta-glucans can massively increase wort viscosity making the beer hard to process gumming up brewing vessels and the like. Oat malt also produces less fermentable sugar per kilo of dry grist than barley malt because it is proportionately more husk, lipid, protein and beta-glucan than barley. Barley malt is the perfect material for brewing, having lots of accessible starch and lots of the enzymes necessary to convert that starch to sugars. But oat malt, while not as good, may still be good enough.

My friend Paul and I started brewing after yesterday’s rugby match between England and New Zealand. Since he is English and I’m a Kiwi, there was a fair bit of good natured banter going on round the sides. Anyway, back to the brewing… We were planning to use the mashing schedule outlined in the research paper. That suggested a rest at 45’C for 20minutes to give proteases in the malt a chance to break down the proteins and beta-glucans to reduce wort viscosity and to ensure there was a sufficient supply of free amino nitrogen (FAN) for healthy yeast. The next rest was to be 62’C which is the optimum temperature for the saccharification enzyme beta-amylase which breaks starch down into sugar. Then we were to raise the temperature to 72’C to the optimum temperature of alpha-amylase to finish off the conversion of starch to sugar. Finally we were to raise the temperature to 77’C to reduce wort viscosity to promote run off. But pulling off a stepped mashing regime like that is quite difficult on a domestic scale and we didn’t quite manage it.

We only have a chilly bin/cooler as a mash tun which means we can’t heat the mash directly. To raise the temperature we need to do either of two things. We can add boiling water to the mash tun to bring it up to the next temperature or we can remove some of the mash to a separate pot and boil it on the stove and add that back to the mash. The first route is much simpler, but you have limited capacity in the mash tun and the greater the volume you have in there, the harder it is to raise the temperature just by adding boiling water. You start needing immense volumes of water. Actually, another way we could do it would be to pump steam through the mash (maybe by connecting a pipe to the kettle and sticking the other end of the pipe into the mash. Steam is hotter than hot water so less would be needed to heat the mash). We tried to do the stepping by starting with a very thick mash 1.5 parts water to 1 part grain. It was very difficult to do this and get the temperature 45’C right. In the end, our rest temperature was 52’C which is probably too hot for the proteases and beta-glucanases to work. Against this, it was very thick. Mash thickness protects heat labile enzymes from the full effects of the temperature. Ultimately, though, I think we botched this stage and that may have stuffed up everything else. The saccharification rest at 62’C was a piece of cake. Getting the alpha-amylase rest was a little harder, but we probably were close enough not to make much odds. At this time, however, there was no more room in the mash tun, so we couldn’t do the final mash out temperature of 77’C. However, our sparge water was that hot so we figured it wouldn’t be too problematic. And indeed wort viscosity wasn’t a problem. The oats have loads of husk which form a filter bed in the mash tun and we had no difficulty running the wort out of the tun into our collection vessel. The wort was intensely cloudy/milky in colour, however, which is definitely not a good sign. We tried recirculating the wort for ages, probably about 10-12 litres, without any noticeable reduction in turbidity so we gave up and collected the wort cloudy.

I think the cloudy wort didn’t play nicely with the boiler. The boiler cut out several times during the boil. We took the wort out again at great effort, cleaned the element and returned the wort to the boil only to realise that we’d forgotten to put the hop strainer back. So we emptied the boiler and put the hop strainer back. Then the boiler cut out again. So we emptied it again and cleaned the element and returned the wort. Then it cut out again… In the end, we probably only had about half an hour of boiling where we might normally have 60-90 minutes. We ended up just dumping a load of hops in and leaving them to steep for ages in hot wort of about 80’C to try to get some bitterness into the beer. It should also mean it will be nice and hoppy tasting as the lower temperature will have driven few of the volatile aromatic compounds off.

The brew should be bubbling away nicely now. And we’ll know in about a week whether it was worth all the effort or not. It was a nice illustration though of how different materials can present processing problems and how the design of a brewery needs to be tailored to the recipe. If we’d had a mash filter instead of a mash tun, we’d have had clear wort going into the boiler, and if we’d used a steam jacketed boiler instead of a boiler with an internal element, we wouldn’t have had problems with the element becoming fouled and cutting out. So. all things considered, some useful lessons learned. But I do hope the beer tastes nice after all this.

* C Klose, A Mauch, S Wunderlich, F Thiele, M. Zarnkow and E Arendt (2011) “Brewing with 100% Oat Malt” Journal of the Institute of Brewing and Distilling, 117(3), 411-421.

7 thoughts on “100% Oat Malt beer

  1. mairij

    Goodness, Ken, what a complicated process. Lets hope the result turns out to be good beer. I’d love to be there to try it. The gluten-free beer could be a market niche, especially if gluten intolerance is something that gets more likely with age. In my case, the gluten intolerance developed in my early to mid-60s.

  2. Dot

    That does sound like tremendously hard work. A good explanation of a complicated process, though – even your wife is beginning to have a vague understanding of how this all works…

  3. damien

    how does it taste? I also made a beer with oat malt. 75% oat, and rest was munich, spec roast, 6 row and chocolate malt. I get a very unusual and strong malty sweet aroma, almost like candy, but it could come from the spec roast. I hopped it right up so it balances out well.

    1. kenanddot

      Surprisingly light in the body and quite fruity. I thought I could detect a graininess in the first couple of bottles we opened but not in later ones. It was a nice substitute for a lager. I would make it again, I think.

  4. It sounds like you certainly did your homework about brewing with oats!

    Did the article say anything about gelatinization? I know that is an issue with other gluten-free grains, where there may be enough diastatic power to fully convert the starch present but the starches don’t fully gelatinize until the enzymes are denatured. This is in addition to the stuff you already mentioned about grain structure and proteins that must be dealt with, especially when home malting. It might explain why the wort was so cloudy, but I am not at all sure if this is a problem for oats. I am assuming this is coincidental and not at all related to gluten itself.

    It is still possible with an even more complicated mash than what you did, where a good amount of the liquid is collected (from the top, so the starches stay behind) after adding the grains but well before any starches gelatinize, so that it may be kept to protect the enzymes while the grain and loose starches are boiled separately. The two are then carefully mixed back together when the temperatures are right and brought to saccharification temperatures. This is Andrew “Milletman” Lavery’s method as described in his two articles. I highly recommend looking for them if you haven’t read them yet–lots of good information there.

    In addition to trying other mashing programs, I wonder if it’d be worthwhile to try something like making oat crystal or Munich-type malts. Andrew did that successfully with millet and I know others online claim to have done so with maize and buckwheat. At least then you have a lot more flavor possibilities without having to add barley malts.

    1. kenanddot

      Thanks for commenting. I believe the gelatinization temperature of oats is actually slightly less than malted barley, but I will have to check to be sure. The mashing protocol you describe sounds a lot like a decoction mash, except there it is usually a thick portion of grain that is removed and boiled (leaving the mash liquor and the rest of the grains in the mash vessel, and when the boiled portion is returned to the mash vessel, it raises the temperature to the next rest temperature. I think Simpsons Malt do an oat crystal. I’ll have to have a look for those articles you mentioned? Do you want a copy of the paper I followed?

      1. Sure, that’d be great to read. Thanks!

        As for Andrew’s articles, it looks like somebody posted them on a website:


        I have seen that mash called a “decantation mash” and yes, it is kind of the opposite of a decoction mash. I think the boiling is used less for temperature control than it is explicitly for gelatinizing the starches of millet and the like.

        Thanks for the Simpsons link. I think I’d seen that “Golden Naked Oats” somewhere before but didn’t realize it was a crystal malt. I think I’ll try to make some myself after I make it with something I know works, like barley or wheat malt. I definitely want to do a 100% oat beer in the next couple of months.

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