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Why 90 minute mash?

 
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KB




Joined: 06 Nov 2014
Posts: 334
Location: Virginia

Working on: Next brew


PostLink    Posted: Sun Feb 25, 2018 4:47 am    Post subject: Why 90 minute mash? Reply with quote


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Why have a 90 minute mash?

I've read many brewing articles stating the 90 or even 60 minute mash is based on older malting techniques or under modified malt.

With today's highly modified malt a 45 minute mash is sufficient.

Thoughts?
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mjo2125




Joined: 27 Feb 2017
Posts: 248
Location: Dayton, OH


PostLink    Posted: Sun Feb 25, 2018 2:57 pm    Post subject: Reply with quote

I recall reading that today's well-modified malts have for the most part done away with beta-glucanese rest which is part of a step mash process. My interpretation is that if your recipe calls for a 90 minute single-infusion mash, then mash is to be performed for 90 minutes. For step mash recipes, some brewers skip the beta-glucanese rest with British and American malts but German and Belgium malts (esp. Pils malts) can benefit from this rest (Ref "Modern Homebrew Recipes")
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kal
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Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Sun Feb 25, 2018 3:10 pm    Post subject: Re: Why 90 minute mash? Reply with quote

KB wrote:
With today's highly modified malt a 45 minute mash is sufficient.

The lower your mash temp, the longer it takes to convert the starches to sugars. So a mash temp of 149F will take longer than 156F.

The important thing to remember is that conversion is not an on-off switch. So you will get more conversion with a 3 hour mash than you do even with a 90 min mash. So depends on the beer. When I make a light lager that I want bone dry, I'll sometimes mash extra long - even 3-4 hours.

Try a beer both ways for yourself!

Kal

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McGruber




Joined: 12 Aug 2014
Posts: 237
Location: Idaho


PostLink    Posted: Mon Feb 26, 2018 5:12 pm    Post subject: Re: Why 90 minute mash? Reply with quote

kal wrote:
The lower your mash temp, the longer it takes to convert the starches to sugars. So a mash temp of 149F will take longer than 156F.

I think this statement is a little misleading. I might be splitting hairs here, but I think this needs some clarification which might be helpful to newer brewers getting started. During fermentation, it's true that an increase in temperature does correlate to a decrease in fermentation time (it speeds it up). However, as far as I know, mash temperature does not have a liner effect on the speed of conversion. In that Hotter does not equal faster.

The mash temperature has to do with which primary enzymes (alpha and beta-amylase) break down the starches (amylase and amylopectin) into fermentable maltose molecules. The science behind it:

B-amylase works to cleave two glucose molecules (aka maltose) off the ends of longer unfermentable starches (long glucose chains) to create small fermentable packets for the yeast to eat. It works best at 143'F (62'C) and can be destroyed and inactive at 149'F (65'C).

A-amylase breaks large chain starches into smaller dextrins (still not readily fermentable, but smaller) and allows B-amylase to bite off more fermentable ends. It works best at 158'F to 164'F (70 - 74'C) and is destroyed at 176'F (80'C).

The fastest rate of mash conversion should happen at the point around 152'F (67'C) where both enzymes are working as close to their optimal ranges as possible and are both working to break down the starches. Amylase is getting cleaved into smaller packets by Alpha, and the fermentable ends are being cleaved by the Beta.

kal wrote:
...you will get more conversion with a 3 hour mash than you do even with a 90 min mash. So depends on the beer. When I make a light lager that I want bone dry, I'll sometimes mash extra long - even 3-4 hours.
Kal

This is mostly true for "appropriate" temperature ranges. If you hold the wort at 143'F then B-amyalse has a long time to work to break down the longer starches and dextrins down. This is why the beer turns out dry - there aren't any longer chain dextrins to contribute sweetness and body - they've all been broken down into fermentable sugars which will yield a dry beer. A longer hold at ideal B-amylase action will certainly create a dryer beer.

A long hold at optimal A-amylase temperature is similar, but A-amylase has a harder (impossible?) time cleaving the ends off of dextrins, so you end up with a beer that is less fermentable and will have more body and sweetness. The longer the hold time, the more dextrin's well be created and the chance to "dry" it out (ferment it) better will also take longer. Note however that at 164'F B-amylase is completely destroyed and inactive - so no matter how long you hold it at 164'F your beer will never become "dry" because the enzyme that creates fermentable maltose cannot work.

As an extreme example just to make a point; a mash at 176'F (80'C) - which is a temperature where both enzymes are destroyed - will not create a fermentable wort in a faster time frame than a wort made at 140'F. In fact, the wort made and held at 176'F will not be "BEER" at all because it won't ferment. It will remain wort despite the presence of yeast, because the yeast cannot eat giant starch molecules (a. in the image below). The mash held at 140'F and for at least 60 min on the other hand will likely be a decent, and somewhat dry beer.

A good way to see if your mash is done converting at 30 min, or 45 min or 90 min (or whenever you want) is to do an Iodine Test. Place a small sample of wort on a white plate or bowl and place a drop or two of iodine from your LHBS on it. If it looks blue/purple then your mash isn't converted to being fermentable (a. in the image below). If it's clear/yellow, then the starches are broken down to ferment easily (d. in the image below). This is any easy test and will cost less than $10 to implement.



IMG_0762.jpg
 Description:
Image: "Starch Degredation during mashing" from Technology Brewing and Malting 5th English Edition - Wolfgang Kunze., page 224
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IMG_0762.jpg




Last edited by McGruber on Mon Feb 26, 2018 7:41 pm; edited 9 times in total
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McGruber




Joined: 12 Aug 2014
Posts: 237
Location: Idaho


PostLink    Posted: Mon Feb 26, 2018 5:37 pm    Post subject: Re: Why 90 minute mash? Reply with quote

KB wrote:
Why have a 90 minute mash?

I've read many brewing articles stating the 90 or even 60 minute mash is based on older malting techniques or under modified malt.

With today's highly modified malt a 45 minute mash is sufficient.

Thoughts?

I wrote a lot of words above. The point is that: YES, a 45 minute mash could be "sufficient" to create a fermentable beer, but a 90 min mash will make a beer that is the desired sweetness/ dryness/ appropriate body/ etc. The difference between the two is making beer, vs making a great beer.
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McGruber




Joined: 12 Aug 2014
Posts: 237
Location: Idaho


PostLink    Posted: Mon Feb 26, 2018 7:07 pm    Post subject: Re: Why 90 minute mash? Reply with quote

kal wrote:
So you will get more conversion with a 3 hour mash than you do even with a 90 min mash. So depends on the beer. When I make a light lager that I want bone dry, I'll sometimes mash extra long - even 3-4 hours. Kal

Clearly I have too much time on my hands today. One more point on this is that there is a finite amount of starch to be converted. A 90 min mash could be equally as effective in creating the same beer (minus negative oxidative effects) as a 5 hour mash.

Stated another way: If you have an orange (a large starch molecule), you can only peel it and separate out the orange slices (maltose) once. The yeast only cares about the slices. If you separate your orange into slices within 90 min, it will still be in the same number of slices 5 hours later no matter how long you stand and look at it. You don't end up with more oranges. It doesn't become more fermentable (or more dry) than it already is once separated into those slices.

Mug
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KB




Joined: 06 Nov 2014
Posts: 334
Location: Virginia

Working on: Next brew


PostLink    Posted: Mon Feb 26, 2018 8:18 pm    Post subject: Reply with quote

Wow! More input than I expected or hoped. Very interesting and informative information.

Thanks.
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kal
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Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Tue Feb 27, 2018 5:49 pm    Post subject: Re: Why 90 minute mash? Reply with quote

McGruber wrote:
kal wrote:
The lower your mash temp, the longer it takes to convert the starches to sugars. So a mash temp of 149F will take longer than 156F.

I think this statement is a little misleading. I might be splitting hairs here, but I think this needs some clarification which might be helpful to newer brewers getting started...

Entirely right McGruber! I was greatly oversimplifying and incorrectly. Temp does not equate to speed, and what gets converted also changes with temp as you mentioned. If I wanted to oversimplify I probably should say something more along the lines:

"The lower your mash temp, the longer it takes to convert the starches to sugars and more starches will be converted too (resulting in a dryer beer as more will ferment out). So a mash temp of 149F will take longer to convert than 156F, but you'll also produce more fermentable sugars if enough time is given."

(or something like that).

But like you said, if you mash high (like the mid 150's or higher) going longer than 90 mins is not likely to yield anything more fermentable/dryer. I only do those really long 3+ hour mashes at *very* low mash temps (like in the mid 140's). Every beer is different.

Thanks for keeping me in check! Thumbs Up

Kal

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