Alpha Amylase And Beta Amylase - Temp Ranges?

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sim

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For what its worth i'll share the rhyme i made when i was learning it:

Alpha up high - top dog,
Beta below - second fiddle.
 

Bribie G

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Necro.

As a BIAB full volume brewer, for about a year now I've been doing just a single infusion mash for 60 - 90 minutes, letting the grains settle and form a bed and very gently raising the bag. This has given me excellent wort clarity and greatly reduced trub, with the advantage of more beer into the cube. So my standard brew lengths of 23L are now down to 22 to fill a keg, with consequent saving of malt and hops - basically a couple of freebie brews per year, not to be sneezed at either.

I've been given a recipe for a historic UK best bitter that in the brewery was given a 30min 64 degree rest then stepped up to a 68 longer rest - for 2 hours total.
Rather than using my paint stirrer to thrash the bejasus out of the mash on ramping up, I wonder what difference it would make to the wort to mash initially at 68 then just let it drift down by itself to 64 over a two hour period?

Of course on raising the bag the wort would then go up through the enzyme ranges again up to boiling. A bit like Keating's J curve. o_O

If there's going to be a big difference I'd probably look at starting thick and adding boiling water gently to ramp up (plan B).
Opinions?
 

manticle

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The theory is covered in previous posts - mashing in higher will give beta a harder run for its money as the denaturing process is accelerated and it generally requires more time to work than alpha.

However in practice, you may notice little to no difference, which means trying it out.
 

TwoCrows

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Mashing Mechanics (temperature effects)

Mash temps explanded............

 

MHB

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~65oC is the Beta peak, 70oC kills it. If you take the mash up to 68oC the working life of the Beta will be fairly short and I suspect you wont get as an attenuateive wort as you are expecting, so sweeter beer. Once denatured enzymes don't come back, they are dead and gone.
Mark
 

Bribie G

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Thanks, was unsure about exactly what temps kill the Beta, and I'm after a fairly dry beer so I'll do the boiling water addition, should get it fairly accurate as I'll just take the water out of the planned liquor volume.

On checking just now, according to a mixing calculator, I'll just need to hold 5L out, heat to 90 degrees then reintroduce it to the 64 degree mash - should get me about spot on.
 

Lyrebird_Cycles

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Since we are discussing this and it took me a while to find an actual answer to the main question (vis how long do the enzymes actually last at different temperatures?):

The thermal decay of each enzyme is given in Muller J Inst Brewing 1991 "The effects of Mashing Temperature and Mash Thickness on Carbohydrate Composition" with the activity being governed by the equation A = Ao e^-kt. The given values of k are 0.0163 for alpha and 0.0434 for beta, both at 65 oC. Use t 1/2 = k/ln(2), we can derive half lives of about 42 minutes and about 16 minutes, again both at 65 oC, which correspond reasonably well with the data in Fig 1 of the paper.

The data in figs 2a to 2d aren't nearly as neat: according to the results given the degradation of beta after 10 min at 75 oC is somehow less than at 65 oC, which is simply not possible.

We can, however, get some useful insight by looking at the changes in activity between temperatures, which shows that the degradation rate of alpha roughly doubles for each 10 oC whilst that of beta roughly triples. Using this to estimate new values of k using the equations
k = 0.0163 * e ^ (0.07* (t-65)) for alpha and k = 0.0434 * e ^ (0.1* (t-65)) for beta and converting this value to a half life as before:

Temperature:....65...70...75...80...85...90
Half life Alpha....42...30...21...15...10...7
Half life Beta.....16...10.....6....3.5...2....1.5

Using piecewise linear approximation and integration, this says that mashing at 68 and allowing to cool to 64 over two hours will give beta activity equivalent to about 24 minutes at 65 degrees.
 
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Bribie G

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Thanks LC, that beta activity would be similar to the 64 degree rest. Would a "reverse mash", however, result in the Beta chomping the ends off the dextrins etc from the initial alpha mash and thus a more fermentable wort than starting at 64 and ramping up to 68?
Thinking here of Palmer's How to Brew and the chainsaw / hacksaw / whippersnipper analogies.
 

Danscraftbeer

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I think. Its all in favor of making beer. The science can seem overwhelming but in the end its what happened in result before science was conceived as science. All by accident. Storable grain got wet, sprouted, dry it out again for storage purposes. Heat it up with water and Holy Shit! Malt! yummo!
Variable freindly
 
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Danscraftbeer

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I cant even remember what I edited. Something trivial for clarification?, Self censoring modern check list of possibly offensive phrases.
Oh shit, it was a phrase in reference of a cat. Sorry Manticle. I remember now.
I think its a dead phrase now anyhow. :)
 

Lyrebird_Cycles

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Thanks LC, that beta activity would be similar to the 64 degree rest. Would a "reverse mash", however, result in the Beta chomping the ends off the dextrins etc from the initial alpha mash and thus a more fermentable
In theory the answer is probably yes but in practice, at home brew / small commercial brewery scale, these small differences will be swamped by the effect of the particle size distribution produced by the available mills so I doubt that you'd see any actual result.

This occurs because one of the constraints on starch breakdown is the rate of diffusion of the enzymes into the endosperm particles. Simple two- or three-roller mills inevitably produce an excessive number of large particles with consequently poor enzyme penetration thus losing potential fermentable extract.

If you had access to a decent mill it would be a whole different ball game, but unfortunately you don't. Nor do I.
 
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Sidney Harbour-Bridge

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I just came across this thread searching for enzyme de-denaturing temperatures, I think LC posted the formula to calculate what I wanted, Thanks LC

Reading through the speculation about reverse mashing, it reminded me that this is what happens in a decoction mash, this thread Bavarian Weissbier Tips includes a decoction mash schedule where the decoction is raised to 62 and returned to the mash to raise the temp to 40 C to create more glucose, similarly you could raise the decoction to 72 for some good strong alpha activity then return to increase mash temp to 60-62 for better beta activity
 

duncbrewer

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For the hot to cold mashing discussed above best chance would be to add the extra malt after cooling to the enzyme temp and then add supplementary enzymes. But seems like a faff to me for probably no gain and more pain. After all you're going to heat to a boil again afterwards unless it's a no boil beer.
 
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Reverse
In theory the answer is probably yes but in practice, at home brew / small commercial brewery scale, these small differences will be swamped by the effect of the particle size distribution produced by the available mills so I doubt that you'd see any actual result.

This occurs because one of the constraints on starch breakdown is the rate of diffusion of the enzymes into the endosperm particles. Simple two- or three-roller mills inevitably produce an excessive number of large particles with consequently poor enzyme penetration thus losing potential fermentable extract.

If you had access to a decent mill it would be a whole different ball game, but unfortunately you don't. Nor do I.
If one could find a screen the right size (archaeologists have a wide assortment), one could always separate the big particles and then use the old Coopers 750. I have done that, and it wasn't nearly as laborious or time-consuming as it sounds. I could mashed for a

I should add that was om a milled-grain order that, oddly, had a lot of barely broken grains. I got the Coopers out rather than use a very long mash.

Good to see you back, Lyrebird.
 
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