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.