Why Not Directly Heat MLT?

[CenturyStanding]

Hey Everyone,

Potentially dumb question. For those of you who use a 3-piece brewing system with keggles (HLT, MLT, kettle), what is the purpose of the Hot Liquor Tank? Since the keggle MLTs are directly heatable (unlike my Rubbermaid coolers), couldn't you put the full quantity water into the MLT, heat it to the appropriate mashing temp, add the full quantity of grain, drain it entirely and be done?

What does the HLT add to the process?

 

[EBloom97]

Well, for one, in the case you describe there would be no sparge. You'd be looking at 60% efficiency at the very best. Your HLT holds and heats your sparge water to rinse the grains of any residual sugars after the initial mash.

 

[Bru]

What you're describing is a "direct fired MLT" as used by the Brutus Ten.
If you search the forum you'll find alot of info on it - Im currently building one.
But the HLT is still needed for sparge water (and for the heat exchanger for those using a HERMS system).
The Brutus 2.0 uses a two keggles instead of three : http://www.alenuts.com/Alenuts/brutus20.html

 

[NiteOwlBrewing]

Plus, heating the mash with grains/sugars present and concentrated will almost certainly caramelize the sugars more than in the boil. This is why I went away from directly firing my mash. Some like the effect, I did not for some of my styles. This, in addition to the aforementioned sparging, necessitates the HLT (or potentially an inline water heater).

 

[CenturyStanding]

Okay, that about answers my questions.

Thanks for the help.

 

[BargainFittings]

Well, for one, in the case you describe there would be no sparge. You'd be looking at 60% efficiency at the very best. Your HLT holds and heats your sparge water to rinse the grains of any residual sugars after the initial mash.

I do not find this to be true at all for no sparge.

On my system at least, for beer with a gravity less than OG of 1.060 I typically get between 70 and 80% efficiency.

The higher efficiency end would be my milds and small house beers. For a typical 1.060 APA I can count on 70%.

I was doing brew in the bag and have since gone to a 2 vessel system and do not do a sparge any more for average and low gravity beers.

 

[EBloom97]

I do not find this to be true at all for no sparge.

On my system at least, for beer with a gravity less than OG of 1.060 I typically get between 70 and 80% efficiency.

The higher efficiency end would be my milds and small house beers. For a typical 1.060 APA I can count on 70%.

I was doing brew in the bag and have since gone to a 2 vessel system and do not do a sparge any more for average and low gravity beers.

I would be interested to know how you are able to pull those numbers with no sparge brewing. I know I couldn't do it. ;-)

 

[DKershner]

I would be interested to know how you are able to pull those numbers with no sparge brewing. I know I couldn't do it. ;-)

https://www.homebrewtalk.com/f36/i-love-no-sparge-brewing-140972/

Good place to start. Typical no-sparge brewing is in between 65-75% eff, I think it tops out around 80%.

 

[Catt22]

Plus, heating the mash with grains/sugars present and concentrated will almost certainly caramelize the sugars more than in the boil.

I have found this not to be true, or at least on my system is isn't. I frequently brew light lagers and I never have caramelization issues. I would think if this were happening it would be very obvious in those beers. It doesn't seem to happen in the boil kettle either and I often run the boil fairly long andd hard when using Pilsner malt.

 

[BargainFittings]

I would be interested to know how you are able to pull those numbers with no sparge brewing. I know I couldn't do it. ;-)

Well I have not done anything greatly different than when I do sparge. I account for the total amount of water including my loses, crush my grain fairly fine and be sure my water profile is correct for the style.

Before I got my pump, I would stir very well before doing the run off. I now use the pump to recirculate the mash and heat it to mash out temps before I run it off.

 

[JuanMoore]

FWIW an HLT isn't absolutely needed even if you want to sparge. You can heat the sparge water in the BK, you just need a bucket or other vessel to hold the first runnings for a minute or two while the the sparge water is being added to the MLT. I did a couple of brews this way when my cooler HLT developed a leak.

 

[schweaty]

I have found this not to be true, or at least on my system is isn't. I frequently brew light lagers and I never have caramelization issues. I would think if this were happening it would be very obvious in those beers. It doesn't seem to happen in the boil kettle either and I often run the boil fairly long andd hard when using Pilsner malt.

I agree with Catt22 on this one. I have a direct fired mash tun and I get absolutely no carmelization. Then again, I constantly recirculate the mash throughout the entire process. Using a gentle heat and keeping the temperature within two degrees of your set point doesn't allow for long periods of direct heat exposure. The false bottom also helps keep the grains off the bottom, thus preventing scorched grains.

 

[Catt22]

I agree with Catt22 on this one. I have a direct fired mash tun and I get absolutely no carmelization. Then again, I constantly recirculate the mash throughout the entire process. Using a gentle heat and keeping the temperature within two degrees of your set point doesn't allow for long periods of direct heat exposure. The false bottom also helps keep the grains off the bottom, thus preventing scorched grains.

+1 I think the MT/FB design. the burner design and how you operate a RIMS makes all the difference in this regard. IOW, all RIMS are not created equal and all of them are sensitive to operator error. A fast circulation rate also helps avoid over heating the wort. I do the continuous circulation thing too.

 

[ClaudiusB]

Plus, heating the mash with grains/sugars present and concentrated will almost certainly caramelize the sugars more than in the boil. This is why I went away from directly firing my mash. Some like the effect, I did not for some of my styles. This, in addition to the aforementioned sparging, necessitates the HLT (or potentially an inline water heater).

I have a direct fired mash tun and false bottom with stirrer and never had a problem, the temperature never gets high enough to caramelize the sugars.


Initial caramelization temperatures of common carbohydrates
Source: Food-Info.net
Sugar Temperature
Fructose 110° C
Galactose 160° C
Glucose 160° C
Maltose 180° C
Saccharose 160° C
Simply speaking, caramelization is the process of removal of water from a sugar followed by isomerization and polymerisation steps.
My mash tun never runs dry.

Cheers,
ClaudiusB

 

[NiteOwlBrewing]

Let me caveat there are certainly ways around caramelization, but my direct fired SS mash tun with no circulation nor false bottom was the culprit of missing my intended color. I stirred while firing the burner, but it didn't help. The bursts were short, but probably hotter than they should have been. The burner was the small diameter one with a 15psi regulator. My boil kettle also has a sandwiched bottom and is boiling a more diluted solution, so I don't seem to experience any issues there.