Home malting

Ken writes:

Following in the footsteps of this very informative post, I’ve been malting a load of barley and it’s been great fun.

Malting is really very straight forward. All it is is sprouting the barley and then stopping it sprouting. Unfortunately, stopping it sprouting is easier said than done, because those little kernels want to turn into to proper barley plants! The way it is typically done is to kiln the malt at low temperature, say with an air-on temperature of 60 degrees celcius. This dries the kernels out and arrests the process of sprouting. It also does it gently enough to avoid denaturing the malt enzymes (amylases) which are needed to convert starch into sugar. It also drives off unpleasant grassy and raw smelling volatiles from the new malt. (What do they smell like? Pretty much like sprouts of other plants. Would you like a beer that smelled like alfalfa?) This is the part of the malting that I think I’ll have most trouble with. I don’t have a kiln. Jon, in the post linked to above, used his oven, but it seems likely it was too hot for the amylases and add to that the fact that the kilning process takes at least 24 hours, running the oven didn’t seem like a cost effective solution.

barley in germination boxes
barley in germination boxes

After soaking the barley for about 20 hours in two sessions (once over night, and once for most of the day), I divided it between these improvised malting boxes. The black dishes are baking trays, the red boxes are office storage boxes.

barley starting to sprout
barley starting to sprout

Here the barley is beginning to sprout.

I left it to germinate for four days and four nights. This is possibly a little on the long side. I found it hard to tell when the germination was complete (complete, that is, from a maltsters’/brewers’ perspective–obviously, the plant has other ideas). What you want is for the acrospire, which will be the shoot of the new plant, to have progressed up the length of the barley corn, maybe three quarters or just about all the way. The plant will have synthesised the amylases we need, but won’t have converted very much of plants starch reserves into new growth yet. The problem is that this growth occurs inside the barley corn so you can’t see how much has happened. I worry that I’ve left it too long before starting drying because the shoot in some individual corns has actually appeared. I’m just hoping that the corns are following a normal distribution and that the bulk of them will be in the sweet zone.

But how to dry it? The malt at germination is about 45% moisture by weight and it has to be dried down to <5%. That's not really achievable without kilning or drying in the oven, but I think I should be able to dry it down to touch dry levels and then freeze it to stop the growth. The drying down to touch dry levels will drive off the volatiles and the freezing will stop the growth until I can brew with it. As far as I'm aware freezing does not denature enzymes although it can breakup cells (but I don't think this will destroy the brewing value of the malt, if anything, breaking up the cells may assist with the starch gelatinisation process. Because I won't have kilned the malt, it should have its full complement of enzymes including betaglucanases for breaking down gum like betaglucans as well as amylases and even limit dextrinase. I should be able to do a proper stepped mash with this malt to produce a highly fermentable wort (but I'm actually just going to do a 60 minute 65C infusion).

Anyway, to dry the malt I decided that the best way to go is to dry it as I dried the hops earlier this year, namely by fashioning a frame with a wire mesh bottom that I could lay across the hatch up into our attic. This way the warm air from the house escaping into the roof space will dry the malt as it passes. I don't know how long this will take, but it'll probably be a couple of days at least. Unfortunately, that malt is going to keep germinating as it dries, so I may lose extract potential as it goes.

c;ose up of screen from below

Here’s a picture of the malt behind the mesh. The mesh is aluminium modeling wire mesh which I found on ebay. It looks very much like the stainless steel mesh of a sieve, but with a weaker metal. I’ve actually torn it slightly already, so I would recommend stainless steel if you can find it.

malt in position (from below)
malt in position (from below)

Here you can see the malt and the drying frame in position from the landing below. The frame doesn’t fit exactly over the hatch because the ladder gets in the way so I’ve also laid cardboard across the gap to direct the air through the malt (as much as possible)

malt in drying frame
malt in drying frame

malt in position (from above)
malt in position (from above)

I’m also making crystal malt at home. What I’ve done here is follow Jon’s procedure as detailed in the earlier post, which is to say, seal it in plastic bags and submerge it in a water bath at mashing temperatures (I went for 65’C), and then grill it in the oven. I mashed for 60 minutes only, which I think was probably too short. 60 minutes is my usual mash length, but now that I think about it, I usually mashing milled malt where the milling serves to break up the starch and make it accessible. But I haven’t milled the crystal malt, so for that reason, 60 minutes is likely to be too short. I’ve tasted it of course, and it is sweet, but quite possibly it would have been much sweeter if I’d mashed for longer. Nevertheless, anything that is not sugar is still starch, so there’s still plenty of brewing value there.

mashing homemade crystal malt
mashing homemade crystal malt

I have a vacuum sealer so the malt is vacuum packed in plastic bags and weighed down by the copper manifold I usually use to separate the wort from the mash. That’s my usual mashtun, which is just a converted chilly bin.
homemade crystal malt
homemade crystal malt

Here’s the finished product. I think it’s going to be quite a light coloured crystal. I could have toasted it for longer, of course, but I’m hopeful I’ll get plenty of colour and flavour off this. I got this down to about 8% moisture after about 40 minutes under the grill. (initial weight 1000g (measured). initial moisture level 45% (assumption). Hence 550g dry weight. Final weight 600g. Hence 50/600.*100 = 8.3% moisture.

Update: 13/11/13
I brewed with the malt today. To estimate the brewing value of the malt and the crystal malt, I took representative values on a dry weight basis 312.5 litre degrees per kilo for the malt and 276 litre degrees per kilo for the crystal (litre degrees per kilo is a way of measuring extract. 100 litre degrees per kilo mens that a kilo of the substance will produce 1 litre of wort of specific gravity 1.100, or two litres of wort of specific gravity 1.050, or four litres of wort of specific gravity 1.025,… you get the picture. Making allowances for the fact that my crystal had a moisture content of 8%, this meant the as is extract potential was only 254 litre degrees per kilo. The malt was much wetter (6.4 kilos of finished malt with a dry basis of 4.72kg = 26.25% moisture. The dry basis weight comes from the original estimate of dry mass of barley less the dry mass taken out to make crystal. 6.2 kg at 15% moisture = 5.27kg dry mass, less 550g = 4.72kg). So the as is litre degrees per kilo of the finished malt was 73.75% of 312.5 = 230.5 ld/kg. I had 6.4kg of malt plus 600g of crystal. I obtained 25 litres of wort of specific gravity 1.038, or a rather derisory extract efficiency of 58.8%. I usually get between 75-80% on my system.

I believe the low extract is directly attributable to problems I had millin the grain which was very wet (26.25% moisture). I took more than three hours to mill the malt and crystal. The grain was too pliable and rather than crumbling into pieces it simply squished between the rollers. After the mash, I could still see blobs of white starch in amongst the spent grain. I went so far as to draw off some of the wort reheat it and add it back to the mash i e hope that added contact time would gelatinise the starch better, but obviously not to any great effect.

Oh well. It is fermenting away now. We will see if it tastes nice after all this extra work.

Update: 10.12.13 – I had a taster of this last night and I have o say I was disappointed. The raw, sprouty smell of the malt was definitely noticeable in the finished beer. Hopefully, it will disappear over time. At this stage, I think it is simply too much work and the products are not of sufficient quality for me to recommend malting at home to anyone. But if you are going to do it, the kilning at the end is the key.

3 thoughts on “Home malting

  1. Mairi Jay

    Ken, I can see you will be a boutique brewer yet. I love the way you are experimenting with the material to hand. It’s very much a ‘kiwi’ characteristic. All the best with your experiments.

  2. Katimum

    When are you going to sow your barley crop? Have you thought of taking up coopering as well? Any way,hope the experiment works out well!

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