Mash temperature fluctuations

[SlitheryDee]

So I had my first BIAB experience last weekend. Everything went pretty smoothly, but I had a question.

The recipe called for a 90 minute mash, so I knew I'd lose a lot of heat during the course of it. With that in mind, I put my grains in when the water was a couple of degrees above what beersmith recommended. That resulted in my initial temperature being 154F, which felt good to me as it would allow the mash to spend most of it's time in the 145-152 degree range as the temps fell.

The insulation I was using proved kind of insufficient for the task, and I found myself firing up the burner twice during the course of the mash to keep the temperature comfortably above 143. The temperature never got away from me like I feared it might, but I still wondered what was happening to my enzymes near the bottom of the kettle where the heat source was. I stirred it constantly while applying heat, and stopped the flame well before the temperature rose to 150, which seemed to work as it would continue to climb a couple of degrees even after I killed the flame. In that way I managed to keep the mash in my target range for the whole 90 minutes.

Everything seems ok so far, but I'm wondering what the swings in temperature might have done to my wort. I'm also wondering if there is any negative effect to doughing in at a slightly high temperature like I did when the mash ended up spending most of it's time in the correct temperature range.

FWIW my OG ended up 4 points higher than I predicted, for an overall brewhouse efficiency of 74.9%. Doesn't seem too bad for a first try, but now I'm wondering what to do with that information. Should I assume ~75% efficiency from now on in order to more precisely dial in my ingredient amounts in the future? Should I give it a few more batches first?

 

[doug293cz]

So I had my first BIAB experience last weekend. Everything went pretty smoothly, but I had a question.

The recipe called for a 90 minute mash, so I knew I'd lose a lot of heat during the course of it. With that in mind, I put my grains in when the water was a couple of degrees above what beersmith recommended. That resulted in my initial temperature being 154F, which felt good to me as it would allow the mash to spend most of it's time in the 145-152 degree range as the temps fell.

The insulation I was using proved kind of insufficient for the task, and I found myself firing up the burner twice during the course of the mash to keep the temperature comfortably above 143. The temperature never got away from me like I feared it might, but I still wondered what was happening to my enzymes near the bottom of the kettle where the heat source was. I stirred it constantly while applying heat, and stopped the flame well before the temperature rose to 150, which seemed to work as it would continue to climb a couple of degrees even after I killed the flame. In that way I managed to keep the mash in my target range for the whole 90 minutes.

Everything seems ok so far, but I'm wondering what the swings in temperature might have done to my wort. I'm also wondering if there is any negative effect to doughing in at a slightly high temperature like I did when the mash ended up spending most of it's time in the correct temperature range.

FWIW my OG ended up 4 points higher than I predicted, for an overall brewhouse efficiency of 74.9%. Doesn't seem too bad for a first try, but now I'm wondering what to do with that information. Should I assume ~75% efficiency from now on in order to more precisely dial in my ingredient amounts in the future? Should I give it a few more batches first?

The temp fluctuations will have little if any effect on your final product. Since you stirred during heat application, you shouldn't have denatured many of the enzymes, since you minimized hot spots. Sounds like you did everything right when applying heat.

Go ahead and use 75% eff for your next brew, keep tracking your eff brew to brew, and you will get an idea of the range your system and process provides, and use the average for recipe planning. Be aware that larger beers (more grain) will have lower eff than smaller beers. You need to take this into account for recipe planning, and when comparing efficiencies batch to batch. It's possible to predict this grain bill size effect on efficiency, so just ask if you want more details.

Brew on

 

[Silver_Is_Money]

If you had a decent quotient of diastatic enzymes it's likely that 80% or more of the starch to sugar conversion happened within the first 20 minutes of the mash. And by 30 minutes it may have passed the iodine test. Temperature drops post 30 minutes into the mash may have been of little to no consequence as a result.

 

[LostHopper]

Slithery: I agree with the comments above but for temp control during the mash I've made a Reflectix coozie for my brew kettle that covers the sides and top. I then slide an old sleeping bag over the whole thing. If it's breezy outside when I'm brewing (HA! I live in Oklahoma) I will cover all of this with a tarp. This setup holds heat extremely well (2-3 degree loss) and I've never had to add heat.

That said, listening to the recent Brulosophy podcast on mash temp it all may be unnecessary.

 

[ebstauffer]

The recipe called for a 90 minute mash

Wow. 90 mins? Regardless of what the recipe calls for I go by a starch test -- quick / simple / accurate and generally negative at 40 minutes. FWIW I too get about 75% for moderate 1050 - 1070 brews. As for those temp flucs... I get them too and finally stopped worrying about them as my beer is pretty good. I too double-layer reflectix kettle-koozie like @LostHopper which I assume helps a bit...

 

[RM-MN]

When you see a recipe that says it needs a 90 minute mash it assumes some basic things. It's assuming you have the same kind of crush and a similar insulated mash tun. It assumes that you have no way to check for conversion and just have to let the mash go long in hopes that everything converts.

You don't have the insulated mash tun, your crush could be way different, and you can easily check for conversion. Those items mean the the instructions do not really apply to you in this situation. Being BIAB means you can get your grains milled finer. That shortens the time needed for conversion. It also increases the efficiency so your expected OG is not what you will get as evidenced by your reported OG (you can do much better with better milling). As Silver is Money said, the bulk of your conversion happened in the first 20 to 30 minutes so your mash temp would have been the 152-154 instead of the planned lower temp.

For your next brew you need to consider the following:
1. Is my grain milled the same as the recipe is based on? With BIAB it doesn't need to be. Grains are milled a bit coarse to accommodate a conventional mash tun and its need for a grain bed for filtering. BIAB can tolerate a much finer milling.
2. Can I maintain the mash temp where it needs to be? Insulation helps but only so much. Sometimes putting the pot where the ambient temp is closer to the mash temp is warranted. A preheated oven can be a good place to set the pot.
3. What will the beer be like if my mash temp varies? In many cases you won't be able to tell the difference in the taste. Your beer may attenuate a little more or a little less but most people are not able to distinguish that in sampling.
4. What will the outcome be if I mill the grain finer and get better efficiency? When you start all grain brewing there is no way to determine ahead of time what the efficiency will be. Hindsight works better but only with respect to planning the next batch. Suppose the recipe predicts 75% efficiency and you hit 80. What will be different and will it be detrimental to the beer? Most of the time the only real difference will be the amount of alcohol in the beer and it isn't likely to be so far off as to ruin the beer.