94% mash efficiency, easy as

We had a ball with Sunday’s brew-day. A slightly later start than normal but otherwise things got under-way as normal – the water was pre-heated, and once the recipe was finalised and weighed out, we milled the grain, the mash profile was programmed in to the Braumeister and then we went to mash in.

That’s about where normal ended and the balls-up began.

Because we like to make about 60L per batch and we use a “50L” Braumeister to brew with, our mashes tend to be on the thick side. So when the grain was added to the malt pipe, it was very surprising to discover that we were looking at a really thin mash. A quick glance around and the worst fear was realised – we had made a big stuff up.

For those that are not familiar with the Braumeister design, it is basically a variant of BIAB but instead of a fabric bag the grist is mashed inside a removable malt-pipe that sits in the middle of the boil kettle. This pipe holds all of the mash in the middle 75% of this pipe, held up by a perforated metal plate and a metal mesh at the bottom, and with the same combination sitting on top, so the grist stays where it should when the Braumeister pumps circulate liquid up through the grain during the mash. The reason we had a really thin mash was because the bottom plate and mesh had not been placed in the malt pipe prior to adding the grist. Everything had sunk to the bottom of the malt-pipe and was sitting on top of one of the heating elements.

Malt-pipe without bottom filter, and malt-pipe with bottom filter. Can YOU tell the difference?

Malt-pipe without bottom filter, and malt-pipe with bottom filter. Can YOU tell the difference?

At this point we realised two things. Firstly, we would need to completely remove everything so we could assemble the malt-pipe correctly. Secondly, there was no way this beer was going to turn out as planned. The mission now was to achieve the first and also work out how on earth we were going to rescue this beer.

The first step we chose was to drain off as much liquid as we could, which was fairly easy because we could just open the tap and pour it out. The second stuff-up of the day was to choose to use the big bucket we normally mill in to to catch this liquid. A fairly innocuous decision it seemed, until we noticed the flood spreading over the floor – it turns out this bucket is great for holding milled grain, but a crack 1cm above the bottom of it makes it useless for holding liquids. A quick shift around and we were draining in to a couple of spare 30L fermenters, whilst idly wondering exactly how much liquid we had lost and how much that was going to cost us in the final beer. Oh, and swearing a fair bit. To be fair, there was also a fair bit of laughing and recognition of the fact that brew-days like this made us very appreciative we were not making 1500L in a commercial brewery. I can imagine a lot more swearing if that had been the case.

Next up, we tipped up the whole Braumeister and nearly everything else – mostly just warm and wet grain – went into another bucket which this time turned out to be fully water-tight. However, some grain missed the bucket and got written-off as the floor is not that clean. A full strip-down of the Braumeister followed, during which some more grain ended up lost in the sink, and then we assembled the malt-pipe as it should have been done to begin with and re-started the mash.

With this mission accomplished (and only about 30 minutes time wasted) thoughts turned to how to rescue the beer.

Our expectation was that with the liquid losses to the floor we would be looking at a lower mash efficiency than normal, resulting in a lower OG. Additionally, we may also have a loss of some of the grain flavour as well due to the grain lost on the floor and the sink. We were not that worried about the flavour, as the grain losses were quite small (and our recipe was experimental and deliberately aggressive with 23% smoked malt and 15% Brown malt) but the mash efficiency was definitely a concern. With the expected final ABV being 4.1% there was not a lot of room to play with. For this we decided to look at the pre-boil gravity and use this to decide whether we wanted to boil for longer or add some DME perhaps. So we made a guess as to the volume of liquid lost to the floor and added this amount of water back in and let the mash finish up.

This brings us to the pre-boil gravity. The usual bickering about refractometer versus hydrometer meant that we ended up using both, which given our level of surprise was probably a good thing. Despite our anticipated efficiency of 80% delivering a pre-boil gravity of 1.043, both ways of measuring agreed we were looking at around 1.051, a massive 14% boost in mash efficiency.

It’s worth mentioning at this point that because the Braumeister allows fully automated step-mashing, and the fact that we quite often plan our brew-days with breaks to fit other things in, over the last 50 brews or so we have had many different mash schedules with multi-steps and/or extended mash times, in some cases even mashing overnight. With all of this variation we have very rarely pushed the efficiency up over 80%. To get an efficiency of 94% can not be explained by the extra 30 minutes of “variously warm and wet” time we added to the simple plan of a single-step 60 minute mash. So we assumed that our total volume was down and the high reading was due to a lower boil volume. Total boil volume is not always easy to assess with the Braumeister when you are up and over the 55L measuring mark.

We also realised that as the liquid losses from the leaky bucket happened almost as soon as we started filling it, this liquid would have come from outside of the malt-pipe and would not have had any contact with the grist. It was effectively just water that we had lost, and perhaps the only problem was we had under-estimated the total volume of the flood and not replaced enough of it.

From here we decided to just roll with it, no further changes were made and we continued with a 60 minute boil. Brew-day finished up relatively straight-forwardly, with the only outstanding question being the final batch size we would end up with. Astonishingly enough we ended up with our intended batch size of 60L, meaning that our new discovery of how to stuff up a brew day didn’t do anything other than turn our planned 60L of 4.1% beer into something closer than 5.1% instead.

A few conversations since have made me wonder whether the real reason for this change is due to water/grain ratios. It is clear that when we brew normally, this ratio is definitely on the low side and for some parts of our experience on Sunday it was much closer to normal. That being said, we are never that focused on pushing efficiency to the max so I am pretty sure this will not become our standard brewing method from here on in.

Recipe and tasting notes will be posted in a few weeks time.


Posted in Homebrew Commentary Tagged with: , , ,

Leave a Reply