Purpose of a beta-glucan rest?

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mccann51

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I've been starting to brew with rye more and I was wondering the exact purpose of a beta-glucan rest. I brew in a bag (BIAB), and I've done beta-glucan rests for a few rye brews, and not done it for a few others. Even when I don't do it, I'm still able to move the grain around in the bag, so mashing is not an issue.

My question: is a beta-glucan rest ONLY to avoid lautering issues in traditional all-grain brewing, or do beta-glucans (or lack thereof) come into play in the finished, fermented beer? Do the yeast utilize beta-glucans, does it affect body, or does it all simply precipitate out during ferment?

My brewing technique at this time is still too inconsistent for me to answer this myself, unfortunately.
 

Gnarlybarley

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I did a quick look at "How to Brew" and it seems like yes, a beta-glucanse rest is only to ease lautering difficulties.
 

texasbrewer73

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Part of this question should be how well modified your rye is. If it's well modified, then yes lautering is the main reason. For less modified rye, a protein rest is necessary.
 

mabrungard

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Pro-brewers are very picky about beta-glucans since those compounds adversely affect clarity. Excessive levels do not precipitate and they stay in the beer. If brewing a Rye beer, a level of haze is a given and would not be a detriment. If brewing an otherwise clear beer style with a dose of rye, then clarity may be more of a concern. A beta rest may be necessary in that case.

The beta-glucans do effect the lauterability of the mash along with some other compounds particular to Rye. If you can adequately lauter the grist, no beta rest is needed.
 
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mccann51

mccann51

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Thanks for the replies. I have no reason to believe the rye malt is not fully modified, I don't have issues with mashing/lautering due BIAB, and I'm generally not a stickler for clarity.

Do high amounts of beta-glucans affect the flavor or body of the beer? I generally associate a certain thickness with rye beers, but I don't know if this is due to beta-glucans or perhaps proteins, or perhaps just the examples I've had of rye beers.
 

mabrungard

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Beta-glucans are big body builders. They are a great way to add viscosity to the wort and subsequent beer, excepting for the clarity issue. I know of several highly accomplished brewers that add a few percent of a grain like unmalted barley, wheat, rye or oats to boost body and mouthfeel.

Unmalted barley has the highest beta-glucan content of brewing grains including oats, rye, and wheat. The thing with rye and wheat is that those grains tend to make up larger percentages of the total grist than unmalted barley. Its interesting to note that when barley is malted, its beta-glucan is reduced to about one-tenth of the raw grain. I haven't found a definitive answer as to if the other grains also undergo a large reduction in beta-glucan content when malted. But I assume those same enzymatic processes in malting effect those grain's beta-glucan content similarly.
 
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mccann51

mccann51

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Thank you, that is the info I was looking for.

Out of curiosity, do beta-glucans also help with head retention? I know high protein content helps with body and head retention, and I'm wondering if body is positively correlated with head retention, or if it's just happenstance that protein increases both of these.
 

pjj2ba

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Thank you, that is the info I was looking for.

Out of curiosity, do beta-glucans also help with head retention? I know high protein content helps with body and head retention, and I'm wondering if body is positively correlated with head retention, or if it's just happenstance that protein increases both of these.
The might help a little in a supporting role, but proteins are the big players as far as head is concerned. The do however increase body.

Another benefit of a beta-glucan (aka fiber/cellulose) rest is in less modified/unmalted grains, these compounds provide a lot of structure to the cells, and slow done the starch conversion process. It is kinda like the starches being held in jail, with the beta-glucans being the bars. Break the bars down and it is much easier for the enzymes to attack the starch.
 
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