Monday, 1 June 2009

Why sugar is inverted

I'd been hoping to find something like this. An explanation of why brewers used invert sugar rather than straight cane sugar:

"It is more usual to add sugars to the wort in which they are fermented together with the maltose of the malt. The sugars generally employed are cane sugar, invert sugar — which is most largely used — and glucose. Refined cane sugar has to be inverted by the yeast before fermentation, and to a certain extent weakens the yeast, favouring the production of lactic acid, so that it is preferable to invert the sugar first."
(Source: "Chemistry for engineers and manufacturers" by Bertram Blount, Arthur George Bloxam, 1896, pages 193-194.)


Oblivious said...

I presume lactic acid is in reference to bacterial infection?

Also I presume this was published before invertase was discovered and know to be secreted

Ron Pattinson said...

Not sure that means an infection. It isn't really clear.

I thought this was understood by 1896. Not 100% sure though, I'll have a look.

Found this:

"Chemical News and Journal of Industrial Science", 1890, page 96. It includes this phrase "the invertase of the yeast".

I'd look at it properly, but I can't see the whole book.

There's this too:

"The best method of estimating cane sugar depends on the hydrolysis of cane sugar by invertase, the enzyme of yeast."

"Dairy chemistry: a practical handbook for dairy chemists" by Henry Droop Richmond, 1899 page 88

So I would say yes, they did know about invertase and that it came from yeast.

ealusceop said...

It's mainly because you give "extra-work" to do for your yeast, some bounds to break (no ref...sorry) that can stress it. Cause lactic acid...maybe, but I think that it's sure that you will get off flavour with refined sugar content of over 20%, I know it, I tried it... This is the famous "cider" taste that you can get. But to cause an infection?

ealusceop said...

What about this, can be useful?

First Stater said...

"This is the famous "cider" taste that you can get."

My latest brews, a mild with sugar and an ordinary bitter without sugar added both smell strongly of apple. I am to the point of giving up on the dry SA-04 Whitbread strain and moving over to a liquid yeast. I strongly believe this is the source, not the sugar.

I wish someone would import the brewer's sugars to the US. Might go to raw grades of sugar and invert myself.

ealusceop said...

"apple", particulary green apple, is not related to sugar, it's another problem. It's called acetaldehyde.

MentalDental said...

"Green apples" are indeed a sign of diacetyl at unacceptably high levels.

This can be due to bacterial infection BUT, if your sanitation is good, is more likely to be yeast related.

Yeast produces diacetyl during early fermentation but later metabolises it to either ethanol (normally) or acetic acid (if the wrong conditions prevail). Green apple taste is a characteristic of immature beer or one that is removed from the yeast too soon.

I would guess that the use of too much sucrose in a beer would lead to high diacetyl levels because of the effect it has on the yeast, mainly due to poor nutrient level or, as Ron's post suggests, knackering the yeast by making it invert all that sugar.

If you brew a beer with high diacetyl level you may remedy it by leaving it in contact with the yeast for longer. Sometimes it helps to get the yeast active again by adding more unfermented wort/malt extract or pitching new active yeast. Then a bit of patience and with a tail wind the diacetyl should disappear.

MentalDental said...

Oops my brain and fingers were not connected. When I typed diacetyl what I meant was acetaldehyde!

Green apples = acetaldehyde.

Sorry about that. It's the beer I had for breakfast.

Oblivious said...

cider flavours has much more to do with poor yeast handling, fermentation, low pitching rates, no oxygenation and the use of bad malt extract than the % of simple sugar.

First Stater said...

Having brewed previous batches with identical apple profile I was anal about sanitation. The result was the same therefore I am blaming the yeast and moving back to a London Ale liquid yeast for future brews. The S04 yeast is highly flocculant, makes me wonder if it drops before it finishes.