mash temp vs fermenbility

Higher temps create sugars that the yeast can not consume and are therefore unfermentable. These unfermentable sugars usually contribute to mouth feel and viscosity. Lower mash temps produce higher fermentable sugars but at the cost of the beer being "thin" I.e. no mouth feel. Check How to brew by John Palmer. He writes a pretty good explanation in it.

 

I think of myself of as more of a Jessie Pinkman rather than a Walter White at this point in my brewing. I can follow recipies (can't spell the word but I can follow 'em) and I can follow directions...however when it comes to the exact nature of the molecular chains and the nitty gritty of it, well, just lead me to the barrel with the bee on it.

 

Bobby from NJ explains it very well in this video:

 

Starches are basically made of really really long sugar molecules. The result of their length is that starches are full bodied and not very sweet. The simplest sugars on the other hand are much smaller molecules. These have no body and are very sweet.

So, when you are mashing, you want to break those long molecules down as much as possible. There are two primary enzymes involved, alpha and beta amylase.

Alpha amylase is kind of like your grain mill, or a rock crusher. It coursely crushes the starches into smaller pieces without turning too much of it into dust. Turn up the heat and it just works faster. Turn down the heat and it works slowly.

Beta amylase acts differently. It can't break up the starches like a mill or crusher, but can only nibble on it a little at a time. Picture beta having a very small mouth, like a child biting into a 5-pound Hershey bar. It's not going to be able to do very much work, and it's going to take a lot longer for it to work. It also doesn't like heat and "dies" or gets broken at higher mash temperatures.

So, you want to hit a mash temp where both the alpha and beta can work together. The alpha breaks things up coursely, and the beta handles the smaller detail work that some would say is the more important of the two. I find that 150 F does the job very nicely -- not too cold for alpha and not too hot for beta. Plus it's a nice round number that's easy to remember!

Key points and ideas:

If you mash too hot, your beta will die fast and your resulting beer will be more dextrinous, full bodied, etc. However you can mash very fast if you don't care about beta. You'll have tons of complex sugars produced in the mash in just 10-20 minutes. Your efficiency will look awesome, but your yeast won't be able to eat very much of it. Attenuation will suffer. You might expect 75% attenuation but only hit 60%.

If you mash too cold, the alpha won't be working very fast. In this case, you might end up with a beer that's too starchy, so it's not very sweet, very cloudy, and again might be full bodied. You can do a really long rest for like 2 hours at like 146 F and get a very good dry beer, it's just that both the beta and alpha work pretty slowly at this temperature so most people don't play much in this area. However you can experiment if you want a super dry beer. For instance you could try activating your alpha at 155 F for just 5-10 minutes, then drop the temperature down to 145 F before the beta all dies for another 90 minutes to theoretically result in a very bone dry beer. So with the same malt bill and same yeast that normally hits 75% attenuation, maybe you could hit 85% or who knows. You can play with it.

That's what I know, in layman's terms.

 

Agree with much of the above. However...

As much as possible implies the most fermentable wort possible, which could be the goal in some cases, but not usually.

 

I miss having him as the president of my homebrew club. Intelligent, great speaker, great educator, and incredibly dedicated / driven homebrewer during those years.

 

And I thought *I* was nitpicky.....

 

It's an excellent video and says the same thing as I did with more technical detail.

 

I don't trust any hotshot that doesn't know the difference between "brake" and "break". : )


This...is why thermometer accuracy and mash tun heat conservation is critical

 

I just wish people would refer to enzymes denaturing...and NOT dying...could give some people the wrong idea.

 

I haven't used that one, but spec-wise it's a little slower and a little less accurate. And it's not quite as highly rated. I own two thermapens, but if I needed a third, I might be tempted to give that thermowand a try. The probe looks a bit shorter too though, and I will say that there are times when my probe length is nearly maxed out. Yes, I said it.

So is it "just as suitable?" I'd say no. But it might be good enough.

 

I usually step mash as described in Noonan's "brewing Lager Beer" by mashing at 148 F 30 minutes, followed by 156F fore an hour. I then mash out at 170. It sea to give a fermentable wort with a drinkable malt profile. It strikes a nice balance of alpha and beta amalayse conditions.

 

@FeDUBBELFIST, thanks for that video. It was EXCELLENT!!

Cheers to Bobby from NJ!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Nitpicky? I dunno. Controlling wort fermentability is the biggest reason people plan/talk about mash temps in the first place. It's not like it's a minor detail.

 

As you've picked up in the replies, temperature control is important. You can get an econ digital thermometer from Thermoworks for under 20 bucks (search Amazon). These guys are just about as accurate as their Big Expensive Brother, they are just slower (~5 secs). You can get good results from them.

You didn't ask, but be aware on your first all grain mash of hot/cold spots in the mash tun. After an initial stir you can still measure a 5-7° difference in grain temps from one side of the tun to the other. The solution is to stir, stir, then stir some more. My recommendation: use a calibrated thermo and have a well-rested stir arm before you add the strike water. If you're off just a couple of degrees the fermentability of the wort changes; which changes the type sugars presented to the yeast, which changes how much alcohol is created, which changes how much residual sugars is left over, which changes . . . well, you get the idea.

There are several online strike-water-mash calculators which help, but expect some trial and error with temps until you have your system zero'ed in. For sure have an extra 1-2 quarts of boiling water standing by for low temps and a bowl of ice if error'ed on the high side.