WILLIAMSWARN BrewMaster, Руководство пользователя

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of typical fermentation rates, as measured by the drop in SG,
are shown is Appendix 7.
The yeast is consuming the sugars, amino acids, vitamins and
minerals and excreting alcohol and CO
2
from its cells into the
wort/must. The SG reduces each day because these compounds,
which are denser than pure water, are being reduced in quantity.
Most of the resulting CO
2
is emitted out the VPRV (we keep
about 10%) and the alcohol stays in the beer. The alcohol is
also less dense than water so the more that is made the lower
the SG becomes as well.
Beers will eventually stop at a certain SG depending on
residual starch in the ingredients and the yeast type. Yeast
cannot eat sugar molecules above 3 sugar units long and
these remain in the beer to give body and some taste. The
amount of these starches (or “dextrins”) depends on how the
malted barley was mashed, the stage in a brewery brewhouse
when crushed grains are mixed with water and starches are
converted into sugars.
For extracts like WilliamsWarn extracts, this is controlled when
the extract is made. All grain brewers can control this themselves
depending on their temperature and time regimes during mashing.
Ingredients made up of mainly sugar, like the musts of cider,
wine and mead, will ferment right down when using a non-
flocculent yeast as they have no residual dextrins because the raw
material is fruit or honey, not starchy grains. We use a very flocculent
yeast for our cider so it stops at about 1.005 – 1.007 if given
sufficient time during fermentation.
SAMPLING AFTER FERMENTATION
Once fermentation is complete, the SG will not reduce any
lower and you can take a final SG sample. This could be
before cooling if the yeast has finished fermenting, but the
most accurate reading is at the very end when the beer is
cleared. This is because if fermentation hasn’t stopped during
cooling, the SG will continue to lower, and in addition, the
clarification process mixes that entire tank contents very well
to make sure you get an accurate reading of the total tank SG.
You will need to take a sample, ensure it is close to 20°C (68°F)
and de-gas the beverage by pouring 150ml between two glasses
before putting it in the measuring cylinder with the hydrometer.
To increase a cold beverage's temperature, you can hold the
glass of sample under a tap of ambient or slightly warm water
while swirling the glass to get a good heat transfer. Then
measure the SG as described above.
CALCULATING % ALCOHOL BY VOLUME (ABV)
The alcohol % cannot be determined by floating the hydrometer
in wort or beer and reading the alcohol scale on the hydrometer.
A calculation is required.
There are various calculations to calculate alcohol by volume
(ABV) from an initial and final SG reading.
Here are some options (you may find others on the internet).
A. A basic calculation is:
(Initial SG x 1000) – (Final SG x 1000)/7.46
So for a beer starting at 1.0454 and finishing at 1.010, the
alcohol content by this formula will be (1045.4-1010)/7.46 =
4.75% alcohol by volume.
B. Another simple formula is that is commonly used is:
ABV = (Initial SG - Final SG) x 131
So in this example:
(1.0454 – 1.010) x 131 = 4.64% abv.
You will note there is a discrepancy between the formulas.
These formulas provide a guideline only as true alcohol is
measured in a lab from the final beverage using equipment
a homebrewer does not possess, so different authors prefer
slightly different formulas.
C. A more complex formula which attempts to provide greater
accuracy at higher specific gravities is:
ABV = (76.08 x (Initial SG-Final SG)/(1.775-Initial SG))
x (Final SG/0.794)
You may want to use this for beverages that have an initial
SG above 1.060.
Using formula B, you can see the effect of a lower Final
S.G. on the ABV.
ORIGINAL SG FINAL SG ABV%
1.0454 1.013 4.24%
1.0454 1.012 4.38%
1.0454 1.011 4.51%
1.0454 1.010 4.64%
1.0454 1.009 4.77%
1.0454 1.008 4.90%
1.0454 1.007 5.03%
The yeast we use for our extracts all ferment to this range, so for
the same starting point with a Standard WilliamsWarn Kit you
will end up with slightly different alcohol %’s.
Nottingham Ale yeast will ferment to about 1.010 in 3 days to
make 4.75% alcohol ales and we use this with our English beer
styles.
S-23 and W34/70 are lager yeasts and will ferment slower than
the ales (they are also fermented at lower temperatures which
slows the process down) but they reduce the SG further to about
1.008 in 5 days. They therefore produce 5.01% alcohol lagers
for 1.0454 initial SG worts.
For our Belgian Beer we use T-58 which will end at about 1.012.
Our cider when added as two cans with yeast nutrient will
produce a 1.038 must and will ferment to 1.007 or just below
and produce a 4.06% alcohol cider. To leave some residual
sweetness in that cider kit you can put the cooling on before the
fermentation is finished to end at 1.010 which will result in a
3.70% cider.