Those are great, Euge. I’m trying to justify the price…hmmm, my birthday’s in a couple weeks… ;D
[quote]And be sure to calibrate them in the mash temp range.
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Good idea!
[quote]Oscar if you keep a bit of ice handy, a handful can drop the mash a couple degrees in those panicky first moments.
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Another good idea… However, as I am getting my system dialed in I am figuring out that there is very little heat loss from HLT to MLT… so instead of going with 10º I will go with 5º which gives me a greater margin of error on the 170º and gets me closer to the target.
A little better every time.
Thanks for correcting me. Learn something new every day.
Reviewing enzymes it appears they were first described in brewers yeast. Once again beer has saved the world!
But I would think that the brewing literature would know if beta- and alpha amylase denaturization is reversible or not.
Brew on
Betcha can’t un-fry an egg ;D
;D
Yeah, some proteins don’t denature reversibly, eggs are a good example. And to your point tom, the brewing literature might have the information, you’re right. But they might not have done the required experiments either, I really don’t know. Clearly the proteins are inactivated at higher temps, and just as clearly they are irreversibly denatured at some point before the fermentation or mash temp profiles would have little meaning. But where is that point where they are irreversibly denatured? Is it just in the boil, or is it some point before that, and if before that, when? Like Kai said, there is a time/temp component, but I haven’t seen any data from the right kind of experiment to determine the answer.
Anyway, I’ll do some digging and see what I can find.
Why don’t we just let Kai do it? 
+1 
I have always thought that 168F was the ideal temp to stop all enzymatic activity. Key word is “stop” but as others have also indicated I’m not sure if that’s irreversible or not. Sounds like some experimentation will be in order to get to the bottom of all of this. :-\
Just so people have a point of reference on this, here’s a great chart from How to Brew…
So, according to tschmidlin, and I have no reason to not believe what he says - I respect his knowledge, if some of these enzymes re-nature what would be the effect of starting hot, say 170f, and letting the mash cool down to 150? Maybe stirring to help it get down over a reasonable period or just leaving the mash tun lid open. Wouldn’t this be a better way to expose the grain to necessary temp (see Denny’s chart) than holding at a set temps or ramping up through the temp ranges.
Just drinking out loud…
I tried that once and it made a much less fermentable wort. One mash had rests at 144°F and 158°F, and the other started at 158°F and dropped to 144°F over the course of about an hour and a half. The control wort had about 65% RDF, and the other was about 45%. I don’t have the notes with me.
Alpha amylase requires the beta amylase products to produce a reasonably fermentable wort. Doing it in reverse would be easier, but isn’t really possible.
This hasn’t worked for me either. If you could start a mash at 160 and leave it for a long time, until say, it dropped to 148, you’d have a very fermentable wort. My experience with this has been the opposite. Sweeter and higher final gravity.
Sean, nice experiment. You should put that on your blog, then I can point brewers to it when the discussion comes up.
While a-amylase is technically able to produce fermetable sugars when it happens to split dextrins that are already short, it is not very good at doing that because its affinity (likelihood to react) to short dextrin chains is fairly low. We really rely on the b-amylase to give us fermentable wort and that enzyme quickly denatures above 65 C (150 F).
Here is a primer about enzymatic reactions that should answer some of the questions that came up: Enzymes - German brewing and more
The graphs are only for illustrative purposes. I created them from an ideal model of an enzymatic reaction.
Kai
Kai…you are brilliant.
I don’t know how you can come up with all of this brewing science so effortlessly. I am truly inspired by your brilliance.
You need to compile all of the info on your website and write a book someday. ;)
It doesn’t make sense to me how enzyme activity increases exponentially when we are taught that it should cease at 168F range. How can you explain this phenomenon from practical standpoint?
This is actually a fairly old article and I’m reaping the benefits of being able to point to it w/o having to type so much ;). When I started reading up on enzymes I found so much detail that is generally overlooked by brewers but which would be at least interesting to the more technically inclined brewers.
The temperature section goes into this detail as well. While the speed of the enzymatic reaction increases with time, the rate at which the enzymes get denatured also increases. High temps mean quicker reactions but also less enzymes. At some temperature the rate of enzyme denaturation is more than what is gained from the increase in reaction speed. This will be a temperature above the temperature optimum for this enzyme. And to make things even more complicated, the temperature optima for enzymes also depend on the length of time allowed for the reaction.
Kai
That would be convenient
This is in line with what I’ve heard from people who have tried it, that the initial temperature of the mash has more of an affect on the final fermentabilty of the wort, so even starting at 155F and letting it drop will yield a less fermentable wort than doing it from low to high. For your experiment, how long was the 144F rest, and how long was the 158F rest, and how long was the mash overall? And for the reverse, how long was it at 144F?
Anyway, the beta amylase clips off maltose and the alpha amylase is random. The alpha gives more ends for the beta to clip, but the beta is the one more active at lower temps.
So why doesn’t it work going from high to low? Is the beta reversibly denatured at a temp as low as 155F? Does a long alpha rest leave a bunch of short chains that are long enough to be unfermentable, but too short for the beta to properly bind and act on? Or is the real trick of the lower fermentation temperature that limit dextrinase is still active at 148F, and that is producing the ends for the beta amylase to act on? I don’t know
I haven’t been able to find anything but it would be good to know exactly what is going on, I’m curious. The answers might be in here. Kai, I don’t suppose you have this book?
This book has some info, but not as much as you can find in Kunze, Briggs or Narziss/Back’s other book (Technologie der Wuerzebereitung).
One important aspect, that we brewers tend to forget, is that a-amylase is also active when the b-amylase is active. So once the starch gelatenizes and there are lots of starch chains to break a-amylase will randomly clip them and provide more substrate (chain ends) to b-amylase.
In the most idealized form the amount of fermentable sugars produced depends on the “time” that b-amylase is active. When I say “time” I actually mean the area (integral) under the time-activity curve. This time can be controlled by temperature, which we do in single infusion mashing, or by the length of the maltose rest, which is done in the Hochkurz mash. Again, this is very much idealized.
If you want to have highly fermentable wort you need to keep b-amylase and possibly also the limit dextrinase active as long as possible while giving it enough dextrins to work on. In brewing this means you need to mash at a low temperature but high enough get the starches gelatenized.
One way around this is to do a decoction mash or like a decoction mash. Pull the liquid out of the mash, raise the temp to 160-170 F and let the mash convert, Then return this back to the liquid to reach a temp of 60F. Now the b-amylase and limit dextrinase have lots of dextrins to work on and they’ll survive much longer at this lower temp. A rest temp that would not have been practical with normal mashing since at this tempt the starch hasn’t gelatenized yet. But this is only a technique for ultra fermentable wort.
Kai
Thanks Kai. I thought I had written it up, but apparently not. And now I can’t find my notes. :-\
They were both 90 minute mashes. The traditional schedule would have been roughly 40 min at each temperature. The test mash dropped continuously over that time. I don’t think I even tracked temperature vs. time, though. Assuming it was roughly linear, it would have spent about 30 min below 149°F.
Clearly I’ll have to re-do this experiment. That could be a good project to keep me occupied between commercials tonight.
What temperatures would be best? Last time I chose 62/70°C for no particular reason. Would going to 60/70°C be expected to yield a more fermentable wort? Or even higher for the alpha rest?
With 60 c you are getting rather close to or below the gelatinization temperature. I’d go with 63 C instead.
Kai
Ah, good point. For some reason I was thinking the gelatinization temperature was lower.
It also depends on the batch of malt that you are using. But 63 C is a good temp.
Kai