question about attenuation of different sugars

[rrosa]

Hi,

This is my first post here. I've been homebrewing for one year and a half, now, in Brazil, and I would like to understand better the attenuation process carried on by the yeast. There are different types of sugar, and each strand of yeast ferments each type of sugar to a different extent. I believe the attenuation percentage claimed for each strand of yeast is an average attenuation, because each particular batch would have a different attenuation depending on the proportion of each sugar in the wort. Now my question is about what type of sugar is left at the end of the fermentation. What, in general, are the attenuation percentage for each type of sugar (dextrose, frutose, maltose, sucrose, maltotriose, maltotetraose, any other?)? Do we still find dextrose, frutose, and maltose in the beer, or only maltotetraose and the other less fermentable sugars? And what stops the yeast from fully fermenting the sugar, just the alchool content? I know this is too technical, but I am really curious. I appreciate any comment.

All the best,
Ricardo

All the best,
Ricardo

[Wilson]

Wow....

Welcome to the site, you sound like you know more about this than I do, but I wanted to say hello to ya. Is there a Biochemist in the house? ;) What is the homebrewing scene like in Rio?

[danno]

Ricardo, I don't know enough about the different types of sugars to answer that part of your question, but I do know the answer to "And what stops the yeast from fully fermenting the sugars?".

during the mashing process, different enzymes break down the starches into sugars. the two we're going to focus on here are the beta-amylase and the alpha-amylase. beta-amylase produces maltose, but it only works on the ends of the starch chain. so, if you focus on a beta-amylase mash, you'll end up with a lot of unfermentables. alpha-amylase has the ability to break up the starch chains in the middle, which will produce a more fermentable mash. beer yeast can only ferment maltose, so any remaining sugars stay in your beer...

Palmer says this a lot more accurately and completely (http://www.howtobrew.com/section3/chapter14-1.html) than I do, hopefully this will point you in the direction of an answer you're looking for...

[rrosa]

Thanks Wilson and danno for your replies.

Yes, the on-line book by J. Palmer is very good. I have a number of other books, too, but they are not so specific. The yeast is actually able to ferment sugars other than maltose, although maltose seems to be present in larger amounts. In one of the books, I read that dextrose and frutose are fermented first and seemingly to nearly 100%, and then comes maltose, which I don't know if it is fermented up to 100%. I know sucrose is also fermented, but not so easily, and besides it is not usually present in the wort unless you add things like table sugar and belgian candy sugar. Galactose is also unfermentable but not found in the wort, unless added artificially to increase the sweetness. I think the most relevant for the sweetness of the beer are maltotriose and maltotetraose, which are also by-products of the mash, and whose proportions in the wort can be controled in the mash process, as you mentioned. They are both fermentable by lager yeast while ale yeast seems to ferment only maltotriose. My curiosity is whether the sweetness comes only from maltotriose (assuming no other sugar is artifically added) of if part of maltotriose and maybe maltose or some other sugar is also present. And also what are the typical proportion of these sugars left in the beer.

As for the homebrewing scene in Brazil, I can say that it is in its infancy. Let me start with the beer scene: Only recently we started seeing "good beers" in specialized markets. We can now get a few belgian beers (only from Interbrew, meaning Leffe, Hoergaarden, Chimay, Duvel, and my favorite Trippel Karmeliet). Not many from other countries, except for Guinness and a German brand which I can't remember the name. As for Brazilians beers, up to ten years ago we could only find Budweiser's kind of beer, but since then there appeared some good microbreweries making very good Stouts, Bocks, and Red Ales.

As for homebrewing, it is starting to get interesting. I know only two or three guys who sell equipment and goods here. They both sell pilsner malt made in Brazil, and only one of them imports crystal and chocolate malt. I myself only buy pilsner and kiln/roast my own versions of crystal, roasted, and vienna malt, although I don't really know if they could be called as such... But it is fun to do that, anyway. We also have a very limited choice of yeasts. I heard from these guys that maybe a few thousand people have made a few batches at some point but I think not many of them kept doing that regularly. But there may be a boom coming up. Let us hope so!

And no biochemist in the house! I am just a curious mathematician.

Glad to participate on this forum, although our "homebrewing scenes" are so different beerwise.

Sorry for the long post...