Unfermentable Sugars

[jiffybrew]

When mashing at higher temperatures you get more unfermentable sugars and thus getting a sweeter beer. What kind of sugars are these? And what makes them unfermentable?
Or... Are all sugars fermentable but it just certain sugars take much longer to ferment?

 

[shafferpilot]

All sugars are fermentable...... depending on what animal is doing the fermentation. Beer yeast is unique for a lot of reasons. One of which is its inability to ferment malto dextrine. I don't know if this is the only unfermentable sugar in beer, but it is the one that I use to back sweeten apfelwine without having to worry about it turning my gallon jugs into grenades. If you look through this chapter on howtobrew.com I think it will provide better answers than I can think of off the top of my head:

http://howtobrew.com/section3/chapter14.html

 

[Sir Humpsalot]

It's really all about the length of the sugar molecule.

The illustrative, non-scientific, description I read somewhere is that you can think of alpha amylase (the enzyme active at higher mash temps) as nibbling at the ends of the long chains of large sugar molecules, whereas the beta amylase (active at lower temps) tends to "bite them in the middle".

As a result, alpha amylase leaves longer chains of sugars (more complex sugars) which are more difficult or impossible for mere beer yeast to ferment... though some wine yeasts and other bacterias may still have a field day with them. As a result, an infection, be it a wild yeast or bacteria, can create bottle bombs in otherwise fully-fermented beer.

 

[shafferpilot]

A good way to think of it Humps, but you have your alpha and beta flipped.

http://howtobrew.com/section3/chapter14-1.html


EDIT: Okay it's fixed now

 

[Sir Humpsalot]

A good way to think of it Humps, but you have your alpha and beta flipped.

http://howtobrew.com/section3/chapter14-1.html

I stand corrected!

Fixed.

Personally, I'm not good with fancy names. I just remember lower temps are for watery beers and big barleywines. Everything else, I mash up higher.

 

[TexLaw]

Yep, those unfermentable sugars are dextrines that are larger chain saccharides. The brewer's yeast just can't handle those. Think of it as if you were eating a steak. You can't swallow the thing whole. You have to cut it or bite it into pieces.

It works the same way for yeast, but they don't have cutlery or teeth. If their Mommy doesn't cut up their sugars for them, they can't eat 'em.


TL

 

[david_42]

At the other end of the spectrum, gut bacteria have NO problems with longer sugars.

 

[zoebisch01]

At the other end of the spectrum, gut bacteria have NO problems with longer sugars.

Hehe, I learned that the hard way with my first harvest of Jerusalem Artichokes

 

[Dr Malt]

Brewers yeast can metabolize sugars made up of one, two and three glucose units ( glucose, maltose, maltotriose). Anything larger than that and they can not metabolize them. Thus, carbohydrate units of of 4, 5 ,6 etc glucose units remain in the beer as unfermentables to provide a sweetness, viscosity and elevated final gravity. Mashing at higher temperatures produces more of these larger carbohydrates due to the high temperature activity of alpha amylase.

This is the chemical version of what what already said. I hope this helps.

Dr Malt

 

[charcoal chuck]

On a similar issue....When formulating recipies and estimating the FG, how does the calculation for apparent attenuation account for unfermentable sugars? Or, is the impacts to gravity from unfermentable sugars small enough to be considered negligable?

 

[broadbill]

Brewers yeast can metabolize sugars made up of one, two and three glucose units ( glucose, maltose, maltotriose).

This isn't quite true either. Lactose is a disaccharide that is not metabolized by yeast...this is why it is used in Stouts to make them Sweet Stouts.

 

[zoebisch01]

On a similar issue....When formulating recipies and estimating the FG, how does the calculation for apparent attenuation account for unfermentable sugars? Or, is the impacts to gravity from unfermentable sugars small enough to be considered negligable?

I believe that the numbers are correct on the charts (roughly). Where you will see small discrepancies is with your mash temperature. There is no way (to my knowledge) that you can directly account for what a high mash temperature will change in your efficiency yield or a low temp for that matter.

 

[TexLaw]

This isn't quite true either. Lactose is a disaccharide that is not metabolized by yeast...this is why it is used in Stouts to make them Sweet Stouts.

Lactose is not made of two glucose units, but of one glucose and one galactose with a different bond.


TL

 

[broadbill]

Lactose is not made of two glucose units, but of one glucose and one galactose with a different bond.


TL

You are correct. I thought he said that yeast can degrade ANY disaccharide. They can degrade any disaccharide that is all glucose (maltose).

 

[Kaiser]

On a similar issue....When formulating recipies and estimating the FG, how does the calculation for apparent attenuation account for unfermentable sugars? Or, is the impacts to gravity from unfermentable sugars small enough to be considered negligable?

I added this to the wiki a wile ago. Maybe it answers some of your questions: https://www.homebrewtalk.com/wiki/index.php/Understanding_Attenuation

Kai

 

[drayman86]

When mashing at higher temperatures you get more unfermentable sugars and thus getting a sweeter beer. What kind of sugars are these? And what makes them unfermentable?
Or... Are all sugars fermentable but it just certain sugars take much longer to ferment?

Unfermentable sugars are highly caramelized sugars, like those in caramel malts, and long chain sugars referred to as dextrins. Dextrin malt and malto-dextrin powder have been previously mentioned in the ingredients chapters. Dextrins are tasteless carbohydrates that hang around, adding some weight and viscosity to the beer. The effect is fairly limited and some brewers suspect that dextrins are a leading cause of "beer farts," when these otherwise unfermentable carbohydrates are finally broken down in the intestines.

Dark caramel and roasted malts like Crystal 80, Crystal 120, Special B, Chocolate Malt, and Roast Barley have a high proportion of unfermentable sugars due to the high degree of caramelization (or charring).

http://howtobrew.com/section4/chapter20-1.html

 

[jiffybrew]

Unfermentable sugars are highly caramelized sugars, like those in caramel malts, and long chain sugars referred to as dextrins. Dextrin malt and malto-dextrin powder have been previously mentioned in the ingredients chapters. Dextrins are tasteless carbohydrates that hang around, adding some weight and viscosity to the beer. The effect is fairly limited and some brewers suspect that dextrins are a leading cause of "beer farts," when these otherwise unfermentable carbohydrates are finally broken down in the intestines.

Dark caramel and roasted malts like Crystal 80, Crystal 120, Special B, Chocolate Malt, and Roast Barley have a high proportion of unfermentable sugars due to the high degree of caramelization (or charring).

http://howtobrew.com/section4/chapter20-1.html

Carmelization... exactly what i was wondering about. Caramel is essentially slightly charred sugar. You take sugar ( sucrose, a disaccharide consisting of a fructose and a glucose with an oxygen bond) add water and heat to make caramel. As you heat the sucrose the bond breaks and you get one glucose molecule and one fructose for every sucrose molecule. Does something happen as you continue to heat the sugar? In my head it seems like the sugars are getting simpler and thus more fermentable not long chains of sugar. How did the caramel wind up with long sugar chain?

On a side note, if dextrin is making me fart. i hate dextrin.

 

[drayman86]

As you heat the sucrose the bond breaks and you get one glucose molecule and one fructose for every sucrose molecule. Does something happen as you continue to heat the sugar? In my head it seems like the sugars are getting simpler and thus more fermentable not long chains of sugar. How did the caramel wind up with long sugar chain?

If I recall correctly, it takes an awful lot of heat energy to break the carbon bonds of sugar molecules, far higher than the 212F we see in our boiling kettles, so I don't think the boiling would serve to do this. Maybe a bit at the very bottom of the pot with a very strong burner flame, but not significantly throughout the wort.

On a side note, if dextrin is making me fart. i hate dextrin.

I kinda' dig farting.

 

[cge0]

Carmelization... exactly what i was wondering about. Caramel is essentially slightly charred sugar. You take sugar ( sucrose, a disaccharide consisting of a fructose and a glucose with an oxygen bond) add water and heat to make caramel. As you heat the sucrose the bond breaks and you get one glucose molecule and one fructose for every sucrose molecule. Does something happen as you continue to heat the sugar? In my head it seems like the sugars are getting simpler and thus more fermentable not long chains of sugar. How did the caramel wind up with long sugar chain?

On a side note, if dextrin is making me fart. i hate dextrin.

Caramelization is the oxidation of sugars. This takes place more frequently at higher temperatures for obvious reasons. Chemicals are given off by this reaction, etc.
Wikipedia ftw?

The simplification of sugars is constantly happening in the body, yet we don't have caramel in our veins. It's just the ester bond between the two sugars being hydrolized (H2O is added). Bonding for a-glucose is usually between carbons 1,4 and 1,6 where a hydroxyl group is present (-OH). These two hydroxyl groups are then enzymatically joined to form an ester bond (-O-) between the two carbons and H2O is a waste product. Cellulose is made from b-glucose and similar bonds are formed in that.

</bio fag>

 

[torbanac]

Is D-Tagatose an unfermentable sugar? Made from Lactose but I assume it's sweeter?
Looking for good tasting back sweetener for ciders.