Is mashing exothermic?

[casebrew]

I just pitched a patch of AG Flat Ass Tired, more or less. When I started the mash, the temp was a bit cool at 140, I had mixed well and waited for thr thermometer to stabolise. So I started heating another gallon of water. Still 140. Water gets hot, ready to add it, and I check the thermo again, now 150! By then the mashing was 10-15 mins old, enough time for the chemistry to start. My guess is that I've always had a hard time hitting mash temps because the mash makes some of it's own heat. How about it takes enegy in the plants to combine sugars into starchs, that heat comes out later? If you've ever made Belgian syrup, and seen how it all-of-a-sudden foams up, is that the exothermic reaction?

Anybody else have any thoughts?

 

[Chairman Cheyco]

I've never heard mention of exothermic mash reactions. I would guess that you had a hot spot somewhere and that it took a bit longer to stabilize. If the temp change was that drastic in every mash because of the conversions going on, it would have been adressed in at least one of the myriad texts on the subject.

 

[BigEd]

Mashes are not exothermic. You didn't mix well enough when mashing in and/or didn't wait long enough for a correct thermometer reading.

 

[ajf]

Mashing may be exothermic to a very small extent, but the reaction is certainly not sufficient to raise the mash temperature by 10 degrees. After 15 minutes today, my mash temp seemed to raise 0.8 degree F, but this could be because of inadequate mixing. If you don't pre-warm the mash tun, there can be a considerable temperature gradient close to the walls of the tun.

-a.

 

[Beer Snob]

I leanred last week that my prior AGs I did not heat the turn well enough. This time I got it reall good and hot. Temperatures stabablized much faster this time.

 

[david_42]

I like to pump boiling water into the tun & then adjust to my strike temperature before adding the grain. I've gotten much better results that way.

 

[casebrew]

So, pouring the heated water into the tun first, then adding the grain a couple minutes later, would help stabilise the temps?--- I'm using a rectangular cooler, so it has corners. I stir pretty good, and at 1 1/3 qts/lb, it's soupy enough to get mixed.

 

[Glibbidy]

I'm no physicist, but I cannot possible see how one may consider the mashing process as exothermic. When I'm mashing in I formulate a strike temp. based on what I want my mash temp to be. In my brewhouse the the magic number is around 11 degrees f.
This means if I heat my strike water to 163, and mash in, the temp of my wort is going to drop and equalize at around 152.

One make make an argument for heating the mash tun, but I personally think it is waste of resources.

It usually takes about 10 minutes before you can enjoy an accurate temp reading, don't forget to stir that mash up good like Bob Marley before you close the lid.

 

[graemhoek]

The hydrolysis of starches and sugars is exothermic but only when the reaction is oxidative. In the case of mashing... probably not.

 

[bvn]

Mashing may be exothermic to a very small extent, but the reaction is certainly not sufficient to raise the mash temperature by 10 degrees. After 15 minutes today, my mash temp seemed to raise 0.8 degree F, but this could be because of inadequate mixing. If you don't pre-warm the mash tun, there can be a considerable temperature gradient close to the walls of the tun.

-a.

I have three kinds of thermometers - chef, floating (slow), and holding (for hotel holding trays in steam tables). No matter which I use the mash temp goes up 1 to 5 degrees (randomly) within 5 minutes after I install the mash tun lid. The temperature never goes down. I have a 24" commercial mixing spoon which I use vigorously. The mash tun is a Coleman Extreme 36 qt. It has 2" thick closed cell walls and will hold the 5+ minute temperature for at least 2 hours (heat loss not measurable).

Given what I have read here, the cause has to be:
- magic
- the universe hates me
- my thermometers hate me

It's hard to justify 40 minutes twiddling with the strike to get the temperature right for a 30 minute beta amylase rest.

The good things found here are:
- mashing is not supposed to be noticeably exothermic
- I am not alone
--- TTFN

 

[dbsmith]

I have three kinds of thermometers - chef, floating (slow), and holding (for hotel holding trays in steam tables). No matter which I use the mash temp goes up 1 to 5 degrees (randomly) within 5 minutes after I install the mash tun lid. The temperature never goes down. I have a 24" commercial mixing spoon which I use vigorously. The mash tun is a Coleman Extreme 36 qt. It has 2" thick closed cell walls and will hold the 5+ minute temperature for at least 2 hours (heat loss not measurable).

Given what I have read here, the cause has to be:
- magic
- the universe hates me
- my thermometers hate me

It's hard to justify 40 minutes twiddling with the strike to get the temperature right for a 30 minute beta amylase rest.

The good things found here are:
- mashing is not supposed to be noticeably exothermic
- I am not alone
--- TTFN

It's quite simple. You have a gradient of heat in your mash. Working on a homebrewing scale, that is just the way it is. No homebrew scale mash is going to have a perfect heat distribution. Even with 'vigorous' stirring. I think you should stir thoroughly, not vigorously, btw. You might splash!

 

[dbsmith]

Also, there can be heat pockets in your strike water as well. I heat my strike water up 2 degrees above what I need, then turn off the heat and stir until the temperature reads to what it needs to be.

 

[cluckk]

So, pouring the heated water into the tun first, then adding the grain a couple minutes later, would help stabilise the temps?--- I'm using a rectangular cooler, so it has corners. I stir pretty good, and at 1 1/3 qts/lb, it's soupy enough to get mixed.

When I am getting ready to mash I heat the water and have Brew Smith ready on my laptop (if you don't have it, get it. It's the best $25 you'll spend). Once I get the water up to near mash temp I ladle about a gallon into my MLT cooler and seal it up for about 10 minutes, splashing it around occasionally (careful because most tops are not water tight). After this I pour the water back into the liquor tank to reheat. Then I place my brew thermometer into the cooler and close the lid to get the temperature. I enter this number into the mash tab on Brew Smith along with the temperature of my grain and the other things it asks for. It then calculates my strike water temperature and quantity for me. Because transferring water with my system lowers the temp around five to seven degrees, I use water that is a few degrees hotter than called for. I pour it into my MLT and once it drops to the temp called for by Brew Smith I mash-in. I give everything a good strong stir and then seal it up and wait 2 minutes for the temperature to stabilize. Finally check the temp and make adjustments if needed. Since I have started doing this I haven't had to make any adjustments but have hit my mash temp dead-on every time.