HERMS, Decoction...and Rice Hulls

[XPLSV]

I bought a Blichmann ProPilot 10 gallon electric HERMS system last summer and have been working my way through many of my favorite recipes since then. Big adjustments on the efficiency calculations, but had that down after two brews. I'm about to brew a Trappist Single recipe on it for the first time and my recipe included a single decoction mash and I would like to stay with that, mostly because of what I believe the maillard reaction adds during the decoction boil. I know there are a lot of threads as to whether that maillard reaction does something or doesn't do something...but that isn't the point of the question I'm about to ask here, so lets skip that part. I tried one similar decoction brew on my HERMS system for a Czech Pils...this was my first brew after putting the system together and the first time I saw my efficiency go through the roof, but let us say that I ended up with a very strong beer in the end...too strong for the style. I pulled a good portion of grains out of the mash tun and heated separately on the stove top for the decoction part of the mash. I managed to clog my HERMS system when I disturbed the grain bed and it was a bit of a mess to get it going, again. In all of my subsequent brews, I haven't attempted another decoction withdrawal from the mash tun and I have had zero problems. This is a good impetus to say "why bother" with the decoction, but not when it comes down to this particular Trappist Single recipe, for me. The thought has crossed my mind to add rice hulls this time around...an easy thing to do, in and of itself, but I have never had rice hulls in a previous decoction and I wonder what effect a boiling temperature might have on the rice hulls. I've never had rice hulls exceed the 168-172 range, in the past. If I add the rice hulls to the grain to help the grain bed formation (and then reformation after disturbing the grain bed to pull the decoction), I will have rice hulls in with the grain when I move it to the decoction boil. Anyone have any knowledge on what a boiling temperature (200 here at 7000 feet elevation) might possibly do to rice hulls? I would not want to be adding some unknown flavor to the beer and am considering just taking my chances with clogging the HERMS circuit without the rice hull addition.

 

[Deadalus]

Approaching your issue from a different direction. I'm guess the false bottom was clogged? Maybe you pulled too much liquid out of the valve too quickly or potentially took more liquid out and your grains were no longer floating over the false bottom. In both cases I am wondering if you created an air space right below the false bottom and squashed grains into the mesh. Drain slow for the first case if you removed liquid that way. Second case would be to only take enough grain/liquid so that the space below the false bottom stays filled. You can't see through metal to tell but ponder whether a grain bill of 2/3 the size would have enough liquid to float your grains in the mash tun based on your system. Maybe measure the dead space. Your description suggests you took more than 1/3? I think a possible solution for both though might be underletting although I don't do that when striking so I may not be describing correctly. But if you were to put your decoction liquid into your BK and grains to the MT, you could pump the liquid back underneath the false bottom from the BK to the MT. I think a good stir might help too. You'd be refloating your grains to some extent and potentially avoiding any clogging. Then resettle the grain bed.

I am not sure if anything might be extracted from rice hulls at boiling temps.

 

[XPLSV]

Approaching your issue from a different direction. I'm guess the false bottom was clogged? Maybe you pulled too much liquid out of the valve too quickly or potentially took more liquid out and your grains were no longer floating over the false bottom. In both cases I am wondering if you created an air space right below the false bottom and squashed grains into the mesh. Drain slow for the first case if you removed liquid that way. Second case would be to only take enough grain/liquid so that the space below the false bottom stays filled. You can't see through metal to tell but ponder whether a grain bill of 2/3 the size would have enough liquid to float your grains in the mash tun based on your system. Maybe measure the dead space. Your description suggests you took more than 1/3? I think a possible solution for both though might be underletting although I don't do that when striking so I may not be describing correctly. But if you were to put your decoction liquid into your BK and grains to the MT, you could pump the liquid back underneath the false bottom from the BK to the MT. I think a good stir might help too. You'd be refloating your grains to some extent and potentially avoiding any clogging. Then resettle the grain bed.

I am not sure if anything might be extracted from rice hulls at boiling temps.

All good points. I have made some adjustments on subsequent batches with regard to flow rate, not turning off the pump, etc. The first two batches I did on the 10 gallon system were 5 gallon batches...which can be done, but there is less depth on the mash bed when doing the 5 gallon batches. Another thought was to not mill the crush as fine, although, I really have not had a problem with the last three or four batches, all of which were 10 gallon.

 

[Deadalus]

Ok yeah, five gallons might potentially be problematic. I have a keg MT, and brew 6 gallons frequently. It has a bit of dead space and with lower gravity beers with smaller grain bills, the mash doesn't float so much at strike in. I've only decocted a few times though and the recipes were not light grain bills so I ddn't have this issue. My false bottom also has big holes in my opinion. Your false bottom is the Blichmann and has those sort of raised disks? Is there a suggested minimum crush size for it? That might be a more subtle issue, where the second settling pushes it to the point of clogging. I do think you'd stand a good chance to fix it if you underlet it, plus I don't think you'd have much of a problem with the volume removed for decoction if you ran a 10 gallon batch. If you tried it again simply as a 10 gallon batch and slowed down the output through the valve you might isolate the problem to the crush if that was it and it happened again.

Of course the rice hulls might solve it too if you get a definitive answer!

 

[XPLSV]

Yes, the Blichmann has that raised disc geometry. After some thoughts and some review of past brewing notes from several years ago, I'm going to skip the decoction and just do a normal mash on this one.

 

[Bobby_M]

Make sure that you're running about 1.5 quarts/per gallon in your mash (maybe even 1.6 to account for volume loss in the pump lines and HERMS). If you're used to the 1.25 ratio of static (non recirculated) mashes, you can really gum things up the first time you recirculate. Be sure to let the grainbed settle under gravity for about 10 minutes before slowly starting up the recirculation. You want the grain particles to naturally fall into a random criss-cross pattern rather than suck everything down into concrete.

If you find yourself overshooting gravity in the future, it's best to just dilute it down and discard excess volume prior to starting the hop schedule.