Re-use of yeast is an old moonshiners trick also known as "sloppin' back".
This refers to adding the mash that was strained out of the wash just prior to
distilling, or the sludge left in the bottom of the fermentor, to the next batch of mash.
As Sam explains ..
I did't strain mine so to speak. I pumped out beer
from the barrel and left the grain. I used about half old and half
new grain. NO YEAST. It is already there. I added water and the same
amount of sugar as when I would start a fresh batch. Stir like crazy
and you only have to wait for 3 days max for the cap to form and fall
and you are ready for a good run. Like I mentioned, third time is the
best as far as taste and quantity in my opinion.
This can be a good source of infection for the next batch, but if it
goes well, it will help boost the yeast count heaps, act as a bit of a source
of nutrients (though its still best to add more of the real stuff like ammonia),
and should help buffer the pH a touch (dropping it a few 10 ths). The yeast that
you're reusing by this technique are those that have already shown themselves to
be quite happy in that type of mash, and are ready to go for the next lot.
It appears that the "Turbo" yeasts are only designed to be used once, and
not reused. Ola Norrman writes ...
Turbo Yeast (a mixture of yeast and nutrients) - shall
never be reused. There are 2 main reasons for this:
- Yeast condition.
During the manufacture of dried yeast, very high
levels of phospholipids are accumulated within the
plasma membrane because the yeast is grown aerobically
(with oxygen). The yeast population which exists at
the end of fermentation has depleted levels making
yeast cells more sensitive during subsequent
fermentations and fermentation more likely to stick.
So the yeast produce and accumulates lipids during its
growth in the yeast factory. Then, during anaerobic
fermentation (without oxygen) in the wash, each new
generation of yeast contains less and less lipids.
Lipids are needed for alcohol tolerance which make
this important to 14% Turbos and far more important to
18% Turbos. If to many generations have passed
(because of reuse of yeast or to little yeast to start
with) the yeast have low "lipid protection" and
alcohol tolerance decrease.
Dried yeast also contains typically 15% Trehalose
which is a "protectant sugar". It gives the yeast cell
internal strength and also is an excellent "start
sugar" for the yeast to use at the start of
fermentation. Cells at the end of fermentation will
typically contain only 2 or 3% Trehalose. Trehalose
protect against the shock when the yeast are mixed in
- Nutrient depletion.
Not relevant for beer, partly relevant for wine but
totally relevant for Turbo. So for Turbo, because the
sugar offers no nutritional value, re-using the yeast
a second time will result in a stuck.
Turbos also contains pH-buffer to give the yeast
perfect pH conditions. Nutrients not only work as
nutrients, they also keep the production of volatiles
down to a minimum. Nutrients are consumed by the
yeast. Re-use of a Good Turbo yeast will also result
in a lot more volatiles in the wash. pH-buffer will
not work in the second batch. There are other
ingredients making the CO2 leave faster, giving the
yeast cells something to claim to and move around in
the fermentation, assist clearing after fermentation
etc. Those functions will also be spoiled as they are
a part of the nutrients.
Nutrient composition are the manufacturers secrets.
One can not simply add some DAP
(diammoniumphosphate) or similar and expect it to work
the same. The first Turbo in the world was made in
Sweden. They are sold under the name Prestige and are
extremely good. At
there is a lot of info about quality Turbos including
a "recipe" telling how "Bad Turbos" are made.
There is also info about yeast strains at:
It is a bit surprising that they not have some never
information here, only old basics.
One could talk about genetic drift and bacterial risks
too, but it is not so important.