Cane Sugar

[Nick JD]

Higher alcohols are produced as part of the pentose phosphate pathway of glucose catabolism - they are largely derived as byproduct of the process of yeast synthesising amino acids.

They do this by breaking down and re-building wort amino acids. The yeast assimilates the wort amino acids and a transamination system strips the amino group and creates a pool of oxo-acids. Required amino acids are re-built by the yeast using these as raw material. Normally yeast has a feedback control system to ensure that it only produces enough alpha-keto-acid (oxo-acids) to synthesise the required amount of amino acids.... but, as the level of assimilable amino acid in the wort drops, the feedback system breaks down and the yeast over produces keto/oxo acids in an attempt to ensure enough amino acids. When it turns out that there isn't enough nitrogen to actually make the amino acids.. the yeast is left with an excess of oxo/keto acids - which it does not tolerate well. So it reduces the keto acids via an aldehyde to their corresponding higher alcohol. By products of the production of keto acids also include things like 2,3 butanedione (diacetyl) 2,3 pentanedione, trans-2-nonenol (carbonyls) all of which are flavour active.

And the classic way to give yourself a nitrogen and thus amino acid deficiency in wort... is to use too much nitrogen deficient adjunct, like sugar.

And there are other things like fatty acids spilling out of the yeast cell due to high glycolytic flux, aldehydes as byproducts of a couple of different pathways and even more higher alcohols produced directly from sugar metabolism. Many of these are increased as growth rate increases and therefore glycolytic flux. And yeast does love to eat the simple sugars... gets em racing along at a great rate of knots.

Differnent parts of this are more likely to happen at different points in fermentation as the balance of nutrients and byproducts in the wort changes. So when you add things like simple sugars and how much of them you add, can profoundly effect beer flavour.

See - whichever decent brewing text you prefer.. they all have the same stuff. Don't ask me for the proper chemistry, I don't have the understanding required - I only have the arm waving version and a mental picture of the pathways and the inputs and outputs.

Enough? or do you want more... I have more, but then again so do you.. you have a good brewing text book, its all in there if you read it and and draw the appropriate conclusions.

TB

I still can't find anything that says high proportions of sucrose = fusels, nor the chemistry. High temperatures, yes ... lots of simple sugars, can't find.

Sure, high amounts of sucrose cause all manner of bad flavour compounds - but that "twang" to me is ethanol out of balance with unfermented carbs.

 

[Stuster]

Higher alcohols are produced as part of the pentose phosphate pathway of glucose catabolism - they are largely derived as byproduct of the process of yeast synthesising amino acids.

<Snip.>

And the classic way to give yourself a nitrogen and thus amino acid deficiency in wort... is to use too much nitrogen deficient adjunct, like sugar.

I still can't find anything that says high proportions of sucrose = fusels, nor the chemistry. High temperatures, yes ... lots of simple sugars, can't find.

Sure, high amounts of sucrose cause all manner of bad flavour compounds - but that "twang" to me is ethanol out of balance with unfermented carbs.

I really think TB has given you the reason here. The chemistry is basically in what I have snipped. Makes sense to me (and thanks for that explanation TB. Really helped me to see what the issues with this might be). Still means that sugar in the wort won't necessarily give you a 'twang', it just depends on the proportion used, if there are enough nutrients present, yeast variety, prevailing wind and so on.

One problem with all this is that the word twang is not exactly descriptive. We may be talking about different things here. Are we talking about a flavour that is sometimes in kit and kilo beers? Something you find in commercial beers which use high levels of sugar? Your own beers? If you say it's ethanol out of balance with unfermented carbs (sugars??), that sounds like a kit and kilo with a kit yeast which has left behind some unfermentables.

 

[MHB]

Sugar (sucrose) is not "BAD" or some evil that home brewers must avoid, the misuse of sugar or any other ingredient will make for worse beer.

There are clearly defined and well understood processes and reactions that go on in brewing and we know that high sugar concentrations in the wort will change the way yeast metabolises the wort.

Unfortunately sugar is easy to misuse, widely available and cheap so we tend to see lots of cases of 'Sugar Abuse" in home brewing.

In high gravity beers where sugar is used, the best results come from allowing the yeast to get well established and reduce the wort gravity before adding the sugar, either incrementally or in one dose, depending on the size of the addition.

A good rule of thumb is to never take the wort gravity above the pitching gravity.

MHB

 

[Thirsty Boy]

I still can't find anything that says high proportions of sucrose = fusels, nor the chemistry. High temperatures, yes ... lots of simple sugars, can't find.

Sure, high amounts of sucrose cause all manner of bad flavour compounds - but that "twang" to me is ethanol out of balance with unfermented carbs.

Well then I am sorry but you didn't read or simply didn't understand what I wrote. That "high levels of simple sugar adjunct is a causal factor in increased fusel alcohol production" is stated as clearly and as simply as that in pretty much all the brewing texts I own. Do some more reading.. if you haven't found it, its because you haven't looked hard enough.

The "twang" is most likely a combination of fusels, esters, aldehydes and booze - but what it most likely isn't, is strictly an ethanol thing - bizarrely enough, trained/experienced tasters know what ethanol tastes like, and if it was ethanol, they would simply say "ethanol" or most likely "alcohol levels out of balance with body and maltiness."

But if its ethanol to you.. well and good. You know what the problem is and how to avoid it. Carry on.

 

[dbod]

I've got the CAMRA book - Brew your own British Real Ale - Graham Wheeler and most of the recipes seem to have small (300g - 23l) amounts of white sugar.

He says it is to replace the invert sugar used by the brewery and recommends adding halfway through the (90 minute) boil.

I've just skipped this part of the recipes so far as I plain didn't want to put white sugar into my bloody beer, irrespective of what Mr Wheeler suggests. I've gone to all this trouble to use fresh malt and hops, I just don't want to put sugar in there.

 

[Bribie G]

You can make perfectly good real ales without adding sugar - grab a tin of Tetleys from Dans and you will note that it's all grain. However it's very low gravity (three point something ABV) and depending on the style you want to emulate then many of the famous UK beers contain sugar or until recently maize or rice. So called real ales are "running beers", a product of the early 20th century made quite differently to Victorian beers and during their journey to the present they have been through a number of 'shocks' such as the two Wars, which sadly normally resulted in a drop in gravity. Edit: and many of the recipes and ingredients in real ales are quite modern, Maris Otter and Challenger hops for example date to the Beatles and the Mini Minor era and bloody Harold Wilson . To say that you will never put sugar in a replica of a real ale is like saying you'll never put Pride of Ringwood in a bloody Australian beer or use an evil bottom fermenting yeast in a German Pils.

A really good reader, published early in the 20th century is: linky. Go backwards and forwards on the pages and there is a thorough treatment of sugars and adjuncts, written almost exactly 100 years ago.