...When cane sugar is used, the acid
environment of the fruit juice allows an enzyme in the yeast called sucrase
(or invertase) to convert the sucrose into the simpler sugars glucose
(dextrose) and laevulose (fructose) which are then fermented. Although this
process takes place almost straight away, it can be argued that it is
better to use sugar that is already inverted. In practise this gives a more
even fermentation and thus an arguably better quality finished wine. The
amateur, however, need not worry about this as the difference is likely to
be negligible. Invert sugar is available to buy, though more costly than
the household variety. On the other hand it is possible to invert some
household sugar before adding it.
Put 8 lb of sugar in a sauce pan with 2 pt water and 1/2 oz citric acid.
Bring slowly to the boil, stiring frequently and boil for 30 mins.
Stir in another 2 pt boiling water and allow to cool.
This can now be stored in jars. When using allow 1¼ pints in place of each
lb of household sugar. Remember that each 4 pints will already contain ¼ oz
of citric acid.
so it seems that the invertase normally found in yeast combined with a
slight acid environment, and some heat from yeast activity, gives the
winemaker's yeast what it needs to break down the fruit sugars.
'UPS474' writes ...
I just did some poolside reading in an old homebrewing book.
Appearantly, white sugar must first be altered by the yeast enzyme
called invertase, before it can be fermented. It may be possible to
avoid the sweet aftertaste in homemade vodka I've been reading about
by using invert sugar instead of expensive corn sugar. Invert sugar
can be made by boiling 2 pounds of ordinary table sugar with one
teaspoonful of citric acid in one pint of water until the solution
takes on a pale golden color, then neutralizing the acidity with
about one teaspoonful of food grade chalk. Even if this doesn't get
rid of the sweet aftertaste, fermentation (especially when going for
20% mash with a turbo yeast) will probably take less time
Ted adds ...
Yes it does work well, but we can dispense with the chalk, yeast likes a low
pH of about 4.5. If your invert sugar is lower you might think about adding
chalk or sodium hydroxide(lye) to adjust the pH.
David says ..
Recently used this process myself to start a batch
after breeding up my starter yeast and was amazed how quick it is and how it
accelerates the fermentation process. Fermentation trap was bubbling away
merrily ten minutes after closing and locking the lid. Can't comment
regarding quality as fermentation is ongoing and havnt distilled the
finished wash yet.
Howard says ..
I always do this myself when I am making a wash.
I always invert the sugar and use a Turbo yeast.
I don't think it makes any significant difference to the purity of the
final result, but I think it speeds up the fermentation process a bit
though. I simmer my sugar solution for about
5-10 mins with a cuppla teaspoons of malic acid, (citric also works) to
bring about inverting.