RIMS slow mash out and low attenuation?

[underdog378]

So here's my dilemma. Been brewing for the past 5 years with a 10 gal cooler all grain set up. Single infusion no mash out. Mash at say 152 and sparge with 170 degree water. My attenuation has always been good if not too much attenuation at times.

My new system that I just finished building is a 10 gallon 120v 1500watt rims system. I've run 3 batches through the system so far and my attenuation has sucked on all 3. My fermentation process is the same, the only thing that's changed is the system. The first 2 batches were about 10% below the listed attenuation range for those yeasts but those recipes also had more specialty malts so that's what I initially attributed it to.

However the most recent batch really has me frustrated. On a double IPA with nearly 95% base malts plus a lb of corn sugar, my gravity with 1056 has gone from 1.073 to 1.028 in about 12 days, and has dropped clear. Mash temp on this one was 152.

All my thermometers match up. Even if they aren't 100% accurate they match exactly my old dial thermometer that I was using on my old system without issue.

My concern is this. Starting at a temp of 152 with 28lbs of grain and a grist ratio of 1.25qts/lb, I'll recirculate holding that temp for 45 minutes before I start my mash out, which ends up taking 25 minutes or longer for the whole mash to stabilize at 168.

I've found one other thread regarding a herms system where they ran into the same problem and eliminating the mash out brought their attenuation levels back to what they were used to. In my head though, conversion should be done and the 20-30mins spent getting to 168 shouldn't in theory affect the fermentability.

By starting to ramp up 45 minutes into the mash am I jumping the gun and getting too much alpha activity with the slow ramp up causing lower fermentability? Would not starting the ramp up until I've hit a full 60 minutes help here? Or, is the ramp up just so slow that I'm spending too much time in the alpha range regardless of starting the mash out 15 minutes early? I seem to have read multiple threads regarding 20 minute mash outs without issue. I'd prefer to do the mash out but I'm just looking for some first hand input here before I start experimenting further (and ending up with more beer than I can get into kegs).

 

[BrunDog]

Are you measuring the output of the liquid coming out of the RIMS tube? If your temp is accurately in the low 150's from top to bottom, something else is going on. Pitching temp, ferm temp control, mash time (are you checking for conversion with iodine at the end?), crush size, yeast pitch volume, yeast health, infection, etc.

 

[blizz81]

I'd try a batch with no mash out and your normal batch sparge procedure.


I would think a ramp up that takes that long isn't giving you much of an effective mash out anyways. Could be wrong. What are you looking to "fix" with the mash out anyways - the "sometimes too much attenuation" you mentioned, perhaps? I don't like to tax my 120V element so I haven't been step mashing or ramping up in any way with my RIMS...I just put the first runnings on heat immediately after the runoff finishes, batch sparge like I always have.

 

[Jaybird]

I think knowing you have been brewing on your system for 5 years is helpful as we know your not new to your process. I think if it was me and I had 3 batches on a new system with the same issue I would do a batch EXACTLY like your last but drop the RIMS altogether and see where you end up. Then I would do yet another and not use the RIMS for anything BUT the mash out. This would tell me if the heating of the mash during re circulation in the RIMS is causing me the issues. I am not really sure WHY it would but I think under the circumstances it will at least give you a baseline to go off of.

Cheers
Jay

 

[underdog378]

Thanks for the input so far.

Temp is being measured coming out the top of the RIMS tube. I'm definitely looking into fermentation issues but the fact that I haven't changed anything on that side of things and have only changed my brew system leads me to believe it's not very likely that's the case.

I don't think I'm trying to fix anything with a mash out, I just liked the idea of getting a little extra efficiency. I'm fly sparging so I also wanted to do it to "lock in" my mash profile, which in reality seems to be affecting it negatively at this point.

I'm definitely going to do a trial but I think I'll start with lengthening the mash before mash out first, and then doing a batch with no mash out. During the actual recirc during the mash the element only clicks on and off infrequently I would have a hard time thinking that would cause any issues, but I'll keep it in mind if I don't have favorable results in the other tests.

 

[blizz81]

During the actual recirc during the mash the element only clicks on and off infrequently I would have a hard time thinking that would cause any issues, but I'll keep it in mind if I don't have favorable results in the other tests.

So long as you have decent flow, I'd think not. No scorching on the element either?

 

[underdog378]

So long as you have decent flow, I'd think not. No scorching on the element either?

Once I backed the crush off a little bit I'm now able to run pretty much full open on the pump. All that's left on the element after a brew day is a thin white film of what I assume is protein that wipes right off with my finger.

 

[BrunDog]

Iodine test?

 

[underdog378]

Iodine test?

No iodine test. Efficiency in the 75-85% range depending on how long my sparge was taking. I suppose if I did a test at the time I start the ramp up it would give me an idea how much if any conversion is left although most of the information I've gone through talks about conversion itself being done within 30 minutes.

 

[BrunDog]

Well it's no guarantee and will give false positives. How fine are you crushing? How big of a RIMS tube is it and how big is your element? It is sound advice above to do a single infusion mash just to rule in the RIMS hardware. Do back to back batches and ferment them side by side.

 

[underdog378]

I don't recall the crush off the top of my head. I wouldn't say it's too coarse, but it is slightly coarser than I was using before. With the finer crush I was compacting the grain bed when recirculating. 1.5" brewers hardware rims tube with 120v 1500 watt 12" element from brewhardware. RTD probe is about an inch from the end of the element.

Running some batches changing a single variable at a time is in the works.

 

[doug293cz]

...

I don't think I'm trying to fix anything with a mash out, I just liked the idea of getting a little extra efficiency. I'm fly sparging so I also wanted to do it to "lock in" my mash profile, which in reality seems to be affecting it negatively at this point.

A mash out only provides improved efficiency if your starch to sugar conversion was incomplete. The higher temp "turbo charges" the conversion rate, but only until the amylase is denatured. After that, it does nothing for efficiency. Since you are getting lower efficiency, it sounds like what you are locking in is a low fermentability sugar profile.

I'm definitely going to do a trial but I think I'll start with lengthening the mash before mash out first, and then doing a batch with no mash out...

Longer mash time is a good idea. More on this below.

Once I backed the crush off a little bit I'm now able to run pretty much full open on the pump. All that's left on the element after a brew day is a thin white film of what I assume is protein that wipes right off with my finger.

Aha! A smoking gun.

No iodine test. Efficiency in the 75-85% range depending on how long my sparge was taking. I suppose if I did a test at the time I start the ramp up it would give me an idea how much if any conversion is left although most of the information I've gone through talks about conversion itself being done within 30 minutes.

Conversion can be complete in 30 minutes or less IF you have a fine enough crush. With a crush coarse enough to allow full throttle recirc, it's unlikely that you would get complete conversion in 30 minutes, or even 45 minutes. Your results appear to be consistent with this.

Conversion requires two steps. The first is gelatinization/dissolution of starch. The second is saccharification (amylase chopping up starch into sugar.) Saccharification cannot occur until the starch chains are fully gelatinized. Gelatinization starts at the surface of the grits and proceeds towards the center. The larger the grits, the longer they take to gelatinize, so the longer it takes to get complete conversion. Thus with coarser crushes, you need longer mashes to get full conversion.

Iodine tests are unreliable, especially if you don't test some of the grits, as that is where remaining starch is most likely to be found. A better way to test for conversion completeness is monitoring the SG of the wort in the mash. It turns out that the maximum achievable SG (100% conversion efficiency) is primarily a function of the mash water to grain ratio. Kai Troester gives a table here for max SG vs. mash thickness. A refractometer is necessary to make real time SG monitoring feasible.

With a fly sparge, you should be getting 80% - 90% or better lauter efficiency, so if your mash efficiency is less than this, it is because of less than 100% conversion efficiency.

Brew on

 

[underdog378]

Thanks Doug. That makes sense to me. The first batch I did in the new system I had a finer crush but couldn't run much flow. That beer had attenuation issues as well, but was fairly high in specialty malt so I'm not sure how much that was my process and how much was my crap recipe.

The last batch I got 83% efficiency but still the attenuation issues. What you're saying about mash out and "turbo charging" the conversion rate. If I had incomplete starch conversion and then did the mash out, my mash is then completing the conversion at the higher temps and therefore less fermentability? Am I understanding that right?

 

[doug293cz]

Thanks Doug. That makes sense to me. The first batch I did in the new system I had a finer crush but couldn't run much flow. That beer had attenuation issues as well, but was fairly high in specialty malt so I'm not sure how much that was my process and how much was my crap recipe.

The last batch I got 83% efficiency but still the attenuation issues. What you're saying about mash out and "turbo charging" the conversion rate. If I had incomplete starch conversion and then did the mash out, my mash is then completing the conversion at the higher temps and therefore less fermentability? Am I understanding that right?

You're welcome.

Yes, the conversion going on at the higher temps of a mash out of an incomplete mash will tend to generate more unfermentable sugar, since the beta amylase will probably be dead by then.

Brew on