Settling a Fermentation prior to Distilling
Settling is probabaly THE best kept secret for getting really neutral spirits
such as those used for gin. If you can really let your wash settle well, maybe even
decanting it into another fermentor to let it settle a second time, then the distillate
will be so much cleaner when distilled.
Once fermentation has finished (eg final specific gravity of
0.990-0.980 reached), turn off the heat, and let the finished yeast settle over
a couple of days to the bottom of the container.
Siphon the clear wash into the still, and you're ready to go.
Be careful to not disturb the yeast layer, because if it gets into the still
it can result in bad smells and flavours. If in a hurry, you can use finings
(eg gelatin - 2g in 100mL to settle 25L) to
help settle/clear the yeast, or try placing the wash in the freezer, to chill
it fast & knock the yeast down. Passing the wash through a simple filter, or even
a couple of paper towels to clear out the remaining yeast will also help
improve the quality you later get. The simplest (& often most effective) technique
though is just time.
There is also a new product available, called "Turbo Clear" which
is said to help : http://www.aquavitae.co.nz/spotlight.html
Jack recommends not to use gelatin ..
Gelatin doesn't work as well in sugar mashes - it works by binding to tannin-
which sugar doesn't have. The best bet is Polyclar AT. It can be done in as
little as a few hours.
The settling/clearing behaviour of yeast depends on the type of yeast you've used.
From Brewing Yeasts
(rehashed a bit)...
Yeast normally reproduces by "budding". During budding a small bubble like protuberance
from the mother cell is formed into which part of the cytoplasm as well as a daughter nucleus,
formed by division, passes. In some yeast strains the mother and daughter cells separate from
one another completely, in other strains the cells remain connected to one another and form
chains. Bottom fermenting yeasts occur mainly as single cells or pairs of cells, whereas top
fermenting yeasts form chains of budding cells. In the case of top fermenting yeasts the
mother and daughter cells remain attached to one another for a longer time and as a result branched
chains are formed. Top fermenting yeasts can be categorised as powdery and flocculent yeasts.
In the case of powdery yeasts the cells remain very finely divided in the fermentation medium and
sink slowly to the bottom only at the end of fermentation. The cells of flocculent yeast, clump
together after a short timeto form large flocs and then settle rapidly. Bottom fermenting
yeasts do not form flocs. Another difference is their ability to fermet the trisaccharide raffinose.
Bottom fermenting yeasts can ferment raffinose completely, whereas top fermenting yeasts can
ferment only a third of the trisacchride. So... flocculent yeasts produce a clear but less fully
fermented beer, whereas powdery yeasts and bottom fermenting yeasts produce a turbid beer with
a high degree of attenuation. They also differ in regard to fermentation temperatures .. bottom
fermenting yeasts are performed between 4-12 °C, whereas top fermenting yeasts use 14-25 °C.
Jack writes ..
It's very easy to clarify in the primary fermentor - just fine it with some
bentonite or some Sparkalloid. Dropping the temperature also helps- say,
down into the 50-60F (10-15C) range. The larger yeast volume in the mash may also
(if you're lucky) may cause the yeast to re-absorb some of the esters they produced
during the ferment as they go dormant- just like in beer brewing with a
long lagering phase.
AuntyEthyl describes his technique ...
The process i use for my turbos at the moment is that I ferment only in the primary fermentor. When the
spec. gravity hits .990. I rack the wash from the sediment, into a clean fermentor.
I then clean my first fermentor and over the period of the next 3 -4 hours. (depending on how lazy I feel) I
continuously pour the wash from one fermentor to the other for 3 or 4 times then let it sit for 30mins, and
This degasses the wash and aids clearing. I then follow the directions for Turbo Clear and add the
first of the two part clearing agent let stand for an hour then add second part leave 24hrs.
Result, nice clear wash
If you have to split the wash (say you've made more than the still can hold), just
pour the remaining wash into a container that will hold the
remains and be full. That is, ensure that the air in the container is
minimalised. By eliminating the air in your container you will lessen the
oxygen thereby lessening the chance of oxidation. This way you will be able
to do the remains in a second run any time. The wash should be quite safe for
weeks. Keep it sealed.
Ian writes ...
Please don't "run" your wash while it is still cloudy - when I started this gratifying
hobby I did just that. The result of distilling all that yeast is you get a
lot of nasties that you could avoid by clearing the wash! Yes, the carbon
polishing removed all the nasties over a period of time - but as we are
striving for excellence - please clarify your wash! I have found a
tremendous difference in the result since I started clarifying my wash.
Filtering it is NOT the way to go - I use Sparkeloid - it clears the whole
batch in 24 hours. Also, just placing the wash in a carboy in a cool place
will do the same job over a longer period of time. When your wash is in a
carboy - preferably glass - you can see the yeast settle to the bottom .
After it has settled, siphon it off - you don't want to suck up the stuff at
the bottom - so put the tip of your siphon hose an inch or two above the
crud at the bottom. You will have a crystal clear wash. With the stuff
remaining in the carboy - I pour or siphon all the loose crap above the
almost firm layer of expired yeast into clear 2 litre soda pop bottles - let
it settle, and use it in the next batch - the clear stuff of course - not
the crud in the bottom.
You should be able to keep your wash happily for weeks or months after its
settled, before distilling it. Mike writes ..
The question was recently raised about storing sugar washes. Almost
any alcohol solution over about 5% ABV can be stored for long times
if oxygen is kept away from them. This means store it in glass or
stainless steel; plastic fermenters will allow oxygen to get in and
your wash will turn into vinegar!
The higher the alcohol content, the easier storage is because the
solution will be self sanitizing from the alcohol.
For longer term storage, the yeast present in the wash may present a
problem. After the sugar is used up in a wash, the yeast initially
will start to process some of the higher molecular weight compounds
that it made during the primary fermentation, and the brew will
actually get cleaner! Both beers and wines often benefit from some
period of "sur lees" (on the yeast)storage. If you are planning a
pot distillation for a flavored beverage, this may be a good step to
take. Experiment and find out!
As time goes on, the yeast do die and split open, changing the
flavor strongly for the worse. For storage longer than a few weeks,
the wash should be "racked" (siphoned)off of the yeast cake that
will have settled out in the bottom and sealed in an air tight glass
or stainless container.It can then be stored for months without problems.
Plastics are not 'impermeable to anything'. They may be considered so for liquids that don't attack them, but their structure makes them relatively porous to gases compared to the dense, amorphous structure of glass. Even steel is very porous to hydrogen! Plastics may therefore be used for long-term storage of chemicals that are not adversely affected by oxidation, but not for sugar washes, where even very small amounts of oxygen can have significant impact. Commercial PET in pop bottle thickness transmits 1.5 to 8 ml of oxygen per square meter per day at room temperature. 'Artificial' corks are made out of carefully selected plastics to have uniform oxygen transmission rates, and are being used because they are more uniform than 'natural' corks, not because they don't allow oxygen in. They have the further advantage of being moisture repellent, unlike 'natural' corks which can soak up wine and so provide a nutrient-rich path for fly or airborne bacteria.
The most common bacterium responsible for production of acetic acid from ethanol is not a member of the lactobacillus family, but is mycoderma aceti, commonly known as Mother of Vinegar. When present in wines, members of the lactobacillus family are responsible for malolactic fermentation, which produces many flavorsome by-products. Far from 'being held in check by the alcohol content', they are responsible for secondary fermentation of new wines that are naturally too high in malic acid, as in Germany, or when particular nuances of taste and flavor are desired, as in the red wines of Burgundy and Bordeaux in France. When present in milk, they produce yoghurt. In contrast, mycoderma aceti, which may be bought in any good brewing shop by those wanting to make their own vinegars, primarily produces acetic acid. In the presence of oxygen, this bacterium oxidises ethanol to acetaldehyde and then to acetic acid. This process can and does occur over long storage times in the best of wines should mycoderma aceti permeate 'natural' corks, in which they can find sustenance and so thrive, resulting in the common complaint that a particularly expensive wine has been 'corked'.