MLT Limiting Attentuation

[Sudz]

Question guys.

For those of you using an electric RIM for mashing, do you have difficultly achieving full attenuation of your worts?

I have a PID direct fired gas system and I suspect I may be denaturing my wort during mashing. I'm considering building an electric RIM tube to put inline with my wort circulation. This would be used in place of the direct gas heating during mashing to more gently manage the temps after strike.

I have concerns for the heating elements (even ulwd) potentially denaturing some fraction of the wort during mashing. I know my mash tun can produce an internal surface temp in some areas of the pot bottom of 172 - 185*F. I have no idea what a low density heating element surface temp might be.

 

[processhead]

Take some random temp measurements of your mash in some different areas of the MLT with a known accurate thermometer. If your mash temperature stays consistant and at the temperature set point you are mashing at, you should be fine.

 

[Ahks]

Take some random temp measurements of your mash in some different areas of the MLT with a known accurate thermometer. If your mash temperature stays consistant and at the temperature set point you are mashing at, you should be fine.

This is not true.

The liquor in contact with heat does have a portion of the enzymes in solution. When you heat them above their denaturing point they denature...

How much affect this has on the end product is hugely variable.

Anecdotally, I moved my temp probe to about an inch above my heating element in my 2vessel kettle rims system and I saw my FGs drop.

 

[Sudz]

Ahks, you are describing my concerns precisely. I've measured temps during mashing at multiple points and actually monitor the grain bed during the process. After the initial strike (~ 15 min) the temps approach about 1 degree separation. At mash's end these are about 1/2 degree apart. It would appear the mash process within the MLT is as it should be, but...

My RIM system consist of a Mash Tun which sits inside a slightly larger Boil Tun. The MT has an internal false bottom with a small drain port on the pot bottom and thepot MT sits about 1 " off the BT bottom. The BT is gas fired and controlled via PID. Wort is circulated from the BT bottom to two places via a portioning valve. First, to the MT grain bed top via a sparge ring for maintaining mash temp. Second, returned to the bottom of the BT via a whirlpool to ensure no hot spots occur during heating. During operation the majority of the returning wort goes to the whirlpool as little mash flow is necessary for assuring mash bed temp.

Brewing is fairly conventional. Strike temp is attained and permitted to stabilize. The grain is mashed in and mash temp is permitted to settle. Typically I target a slightly low mash-in temp since raising temp is much easier than lowing the same.

During mashing, the PID barely bumps the gas on to maintain the mash temps. But it does heat the BT bottom to a point where the denaturing of circulating wort is a possibility "I think". I've measured the inside bottom of the boil tun (no MLT installed) with a FLIR gun while heating and maintaining water at mashing temps. The temp at the pot's heated surface varies from 174*F to about 185*F for a 150*F mash. This doesn't seem unreasonable and I suspect an electric heating element could have similar surface temp characteristics.

This whole question arises from my fermentations consistently failing to achieve full attenuation. I've ruled out normal things such as pitching rates, oxygenation, nutrients, temp control, etc which leaves something amiss with my process. If the worts are partially denatured, it would explain the limited attenuation.

 

[processhead]

I should have read your original post more closely, Sudz.
With your gas fired system, I can definitely envision the spot heating taking its toll and denaturing some enzymes.
With a RIMS electric heater, I feel the heat addition can be more precisely controlled.

 

[Ahks]

Yeah. When I started trying to troubleshoot my brew, I took temp measurements from several places and noticed that when I set my mash temp to 149F, I observed the temp of the water/wort in my BK/HLT above the heating element was regularly 20+F higher than the wort I was pumping from the vicinity of the element. Thermodynamics are a *****?

 

[Sudz]

As a follow up to "Direct Heated Mash Tun Temps on Gas Fired Systems", I collected some additional data.

Several thermocouples were placed at random positions on the floor of the boil kettle about 1/8" off the surface. The BT was heated with 8 gal of water to 150*F and permitted it to stabilize via PID gas management and full vortex circulation. Gas heating had been minimized by adjusting the burner flame to it's lowest level.

The water within the pot was 150 degrees +/- 0.1 within 20 minutes until you approached the very bottom. The bottom thermalcouples measured 164 - 170*F which corresponded with earlier FLIR readings. Clearly those temps would denature some percentage of mash activity being circulated. I believe this confirms my concern and may explain my limited attentuation observations on this system.

My plan to move to electric mash thermal control via a RIM tube appears to be justified assuming element surface temps are closer to the desired set point. I'm guessing the relative high circulation flow in a RIM tube coupled with a ULWD element would limit the local heat rise to something more acceptable.

As Ahks points out. Thermodynamics are indeed a *****.

Ahks, when you observed your 20*F delta, were you using a ULWD or LWD element? Were you able to resolve this somehow?

 

[Ahks]

I run this element https://www.brewhardware.com/product_p/element2200.htm which is effectively LWD

Since I run 2v k-rims, I place my reference probe directly above the element so I'm really regulating wort temperature and ignore the few degrees loss to the mash. Where I have my probe is the hottest spot in my system from my observation. So I heat my wort to that reference and pump from a slightly cooler spot in the kettle.

My process almost always includes a step mash in something like a Hochkurz step mash, too, since I like high attenuation. So I start low and ramp over a long period recirculating the whole time.

 

[Sudz]

I just ordered Brewhardware's 240v 5500w element. I plan on running on 120v for about 1350W and a 31W/in2. This is the lowest watt density I could find looking at both standard heating elements and cartridge heaters.

Since you are running well with the 20*F element temp rise, I assume any denaturing is simply insignificant statistically. This helps me to feel good about moving my mash heating to an electric RIM tube to help mitigate the potential for denaturing. The surface area of the bottom of my brew pot is very significant when considering wort exposure to the 160 -170* surface temps over 60 - 90 minutes. Clearly the heating element surface area is much less and the flow across the element in a RIM tube much greater. Both of these help to limit wort exposure to detrimental effects during mashing.

This all sounds good but the final analysis with be if I see improved attenuation after implementing the change.

Thanks for the help Ahks...

 

[processhead]

I think the higher flow rates attainable in a RIMS tube and relatively low watt density are the two keys to solving the denaturing issue for you. Your element choice should work for you.
I am using a 4200 Watt element operated on 120 volts for a 1050 watts output in my home made RIMS tube.
It seems to be more than adequate for mashing grain bills up to about 22 lbs, which is actually more of a limitation of my MLT.

 

[Ahks]

Good point on the flow rate through the tube. That is the sticky failure of my kettle RIMS. I'm sure the flow rate of wort over my element is significantly lower. I'm tempted to build a RIMS tube for this reason, and use my kettle for boil only