Author Topic: Beta-Glucans and Fermentability, Body and Head.  (Read 2076 times)

Offline bspisak

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Beta-Glucans and Fermentability, Body and Head.
« on: May 14, 2010, 11:56:07 PM »
Noonan in New Lager Brewing pp26 says,

"One of the consequences of forced malting is insufficient hydrolysis of beta-glucans to glucose by beta-glucanase enzymes which are denatured above 140F and do not usually survive kilning.... With reasonably well converted malt, manageable amounts of beta-glucans may be liberated from hemicellulose by proteolytic enzymes during a 95-113F (35-45C) mash rest and contribute to a beer's fermentability, body, and foam head."

Palmer in How to Brew, 3rd pp145 says,

"Most of the beta glucan in barley is degraded during malting (from 4 to 6% by weight to less than 0.5%) ... for well-modified malts."

What this seems to be saying is that for well-modified malts, beta-glucanase has been denatured and is no  longer available to break down the 0.5% of remaining beta-glucans. However, by resting the mash at 95-113F the proteolytic (!?) enzymes will free up these remaining beta-glucans such that they can contribute to a beer's fermentabilty, body and head.

So, does this make sense to anyone?


Offline Kaiser

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Re: Beta-Glucans and Fermentability, Body and Head.
« Reply #1 on: May 15, 2010, 05:35:51 AM »
Beta glucanase does survive kilning in lightly kilned malts but does get denatured in more highly kilned malts. Modification itself does little to affect that enzyme but it does reduce the beta glucans.

There is another part to the beta glucan storry that is generally not taught. Two sets of enzymes take effect here. One is the beta-glucanases which break down beta glucans and the other is the beta-glucan solubilases. Those make beta glucans soluble and have a temp optimum between 60 and 70C (140-160F). Therein lies the propblem. In mashing a majority of the beta  glucans can be released, made soluble, through these solubilase enymes but this happens well after the denaturation of the enzymes that can break them down.

As a result cytolysis (the act of breaking down cell walls and with it beta glucans) is one of the primary tasks of malting since it cannot efficiently be done in mashing. During malting both these enzymes (solubilases and glucanases) remain active.

So yes, mashing at regular temps can release more beta glucans but the amount released is generally unproblematic for well modified malts. I have also read in a number of sources that an extended rest at 160F (45-60 min) can improve body and head retention. But ths seems to be largely a result of the release of glycoproteides (I don't think they are the same as b-glucans) when there are no enzymes left that could break them down.

I doubt that the b-glucans will have a large effect on fermentabiliy. While they are unfermentable they are only present in very small amounts. Even in small amounts they can have a signifgicant effect on the beer's viscosity. The latter is what affects lauterability and mouthfeel.

Kai

Offline tom

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Re: Beta-Glucans and Fermentability, Body and Head.
« Reply #2 on: May 16, 2010, 10:29:08 AM »
Kai,
Any evidence that the Wheat beer decoction 140-104-140 would work for this. And why would one want to?
TIA, Tom
Brew on

Offline Kaiser

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Re: Beta-Glucans and Fermentability, Body and Head.
« Reply #3 on: May 16, 2010, 04:43:20 PM »
Kai,
Any evidence that the Wheat beer decoction 140-104-140 would work for this. And why would one want to?
TIA, Tom

The reserach on this maltase mashing, which you seem to refer to, done by Markus Herman does note that this mashing also reduces beta glucans. But the many wheat beers that are brewed w/o this technique show you that it is not needed.

However, It would be interesting to brew a side-by-side with a Roggenbier where the amount of rye usually causes very viscous and hard to work with wort.

Kai

Offline bspisak

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Re: Beta-Glucans and Fermentability, Body and Head.
« Reply #4 on: May 16, 2010, 06:39:26 PM »
I found another reference to this chicken and egg problem of beta glucanase and beta solubilase activation temperatures.

In The Function of Enzymes in Brewing, Tim O'Rourke talks about it, then goes on to say that "it is common practice in many breweries to add exogenous beta-glucanase to decrease wort and beer viscosity and to improve filterability."

Back to Noonan's statement that small "amounts of beta-glucans ... contribute to a beer's fermentability, body, and foam head."  I can see how fermentability and body are affected, but what do we know about head retention as it relates to beta-glucans?

Brian



Offline Kaiser

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Re: Beta-Glucans and Fermentability, Body and Head.
« Reply #5 on: May 16, 2010, 07:59:41 PM »
but what do we know about head retention as it relates to beta-glucans?

could it be the increased viscosity of the beer?

Kai

Offline bspisak

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Re: Beta-Glucans and Fermentability, Body and Head.
« Reply #6 on: May 16, 2010, 08:37:27 PM »
Look and ye shall find:

Stabilize emulsions and foams using barley beta-glucan.

"Barley beta-glucan is receiving increasing attention as a food hydrocolloid (a substance that forms a gel with water). As you know, hydrocolloids are added to foams and emulsions in order to increase the viscosity of the continuous phase, decrease bubble and droplet movement, and slow drainage and creaming. This results in more stable foams and emulsions."

Brian