|
 Our focus on
analytical tests and testing. Tips and advice.
As we research the literature, perform our
own laboratory research and work with the standardized test
protocols and methods in the industry we will attempt, on
this page, to report tricks and tips to help our clients
better understand some of the tests performed on their
products and to guide them if performing some of these tests
in their own laboratories.
Analytical Tricks
and Tips (#1): The First Tip (Brewers:
Bitterness Testing)
may now be found as A pdf-link via the
Archives Page.
NEW,
8-8-05: Analytical Tricks
and Tips (#2)
This second test tip also arises as a result of
numerous client requests (including one from Tibet!) for a
simple way to test the alcohol levels of their productions.
IT MUST BE NOTED THAT THIS IS
NOT AN OFFICIAL METHOD:
It is only
a quick, though very useful, check for alcohol content.
The method described is applicable to beer and to wine.
[Note;
as for all lab methods there are some dangers involved in
carrying out even this simple assay. It should be attempted
by qualified personnel only. We cannot be held
responsible for any actions taken or for accidents occurring
or for any results obtained. Use appropriate,
authentic and intact laboratory glassware and equipment at
all times].
Beer: Indirect
Measurement of Alcohol:
-
Measure exactly 250 mL of beer (use a volumetric flask)
and place into a large beaker (e.g., use a 500 mL or
1000 mL graduated beaker). Rinse the volumetric flask
out with about 100 mL of distilled water and add to the
beaker.
-
Slowly boil
the beer (avoid splashing and losses) until about 2/3rds
of the volume has been lost to evaporation.
[ A heated
mantle would work best for this - with even heating- but
a Bunsen burner set-up could also be used.]
-
Cool
the beer to about room temperature (if necessary use an
ice-water bath to help speed cooling - but CAUTION! -
only do this with partially cooled Pyrex or other
Lab-spec. glassware). When cooled, return the beer
to the volumetric flask and bring the volume back to 250
mL with water. [Use water that has been used to rinse
out the beaker for this; you then get a quantitative
transfer of all the extract minus alcohol.]
-
Use a very
clean (and appropriate) Plato hydrometer to measure the
extract content of the sample; this will be the real
extract of the beer (RE). [Make any necessary
temperature-dependent adjustments to the readings using
correction tables.]
-
While the
beer is boiling (step 2) take a hydrometer and measure
the apparent extract (AE) on a portion of the same beer
that has been degassed (pass back and forth, several
times, between two containers to degas or pass it
through filter paper). [Again make appropriate
adjustments to readings based on the actual
temperature at which the measurement is made.]
Calculate alcohol by weight from the formula:
Alcohol (weight) = 2.22 (RE - AE) [Use 2.23 for
beers
above 13 OPlato]
If
done carefully this method will give fairly accurate
values, though they will not be applicable to BATF (TTB)
standards and should not be used for official purposes.
[TTB/official values are critically dependent upon
temperature as well as on the use of much more
sophisticated equipment/instrumentation in order to get
truly accurate values. At Brewing and Distilling we use
only the best and latest equipment from Anton Paar USA.]
Please call us
if you would rather express your values in alcohol by volume
terms and we can help you there.
[As a starting point for you
here see the wine method below and use that equation for a
rough volume estimate using a factor of 1.42.]
Use these
methods as a rough guide in your own laboratories for
alcohol contents and for process-change evaluations.
Then Get A
Qualified Lab to run samples for confirmation and for
"certified" labeling purposes. {Brewing and Distilling
Analytical Services comes to mind here!}
Wine: Indirect
Measurement of Alcohol:
A similar
procedure to the one given above for beer has been presented
that is applicable to wine (see
www.monashscientific.com.au/BoilingMethod.htm for
complete original details). However, we have found the
need to modify a factor in the calculation supplied by
Monash Scientific in order to get reliable accurate results.
Wine samples may
need a more careful attention to the boiling step (possibly
using a few boiling chips/granules).
The Monash
method calls for the use of distillation apparatus which is
fine though more expensive to set up. Adapt the boiling
procedure above.
Use an
appropriate Specific Gravity Hydrometer. Chart values for
temperature compensation of hydrometer readings can be found
at the Monash site.
Calculations;
The Equation to
use here (for volume alcohol) is:
Alcohol (% v/v
EtOH) = SG2-SG1/ Factor* x 1000
* Factor given
at Monash is 2.11. However, in careful determinations
in our own laboratory, we have found the factor value that
should be used is 1.29 at least for wines in the 10-15%
alcohol by volume range. [REPEAT, WE USE THE VALUE 1.29!]
[Winemakers
usually express wine alcohol content by volume but if you
wish to convert to alcohol by weight please call us and we
will show you how to convert your volume values.]
Using this
method, and the "correct factor" (1.29) in the equation we
have estimated a wine (of true - by official methods - value
at 13.38% by volume) to give a value of 13.41% alc. by
volume at 20 0C. [Note: we used a density meter
rather than a hydrometer for our gravity determinations so
our values will be more accurate than if using a
hydrometer.]
Winemakers: We
recommend that you approach this assay with a bit more
caution (than brewers) and verify for yourselves the factor value
needed in the equation. [Study the method carefully
also at the Monash Scientific website:
www.monashscientific.com.au/BoilingMethod.htm.] It should
however, with careful preparation and attention to detail, work well
for you. Check out the method by using a reputable lab
for confirmation of results and always for Officially
Reliable Values.
Method for Distilled
Spirits/Higher Alcohol Containing Beverages: Indirect
Measurement of Alcohol:
CAUTION! For higher alcohol containing beverages a
word of caution is necessary here. DO NOT USE OPEN
FLAMES FOR SUCH WORK! Use, instead, a heating mantle
(appropriately grounded), and a water bath (boiling on the mantle) with the sample placed above the boiling water to
effect evaporation of the alcohol in the sample. This
will, naturally, take a long time to attain the required 2/3rd volume
reduction.
The method
should work (as described above for beer and wine) with use
of appropriate hydrometers and with the establishment of an
appropriate factor for the equation. Some experimentation
will be necessary on your part to establish the best
conditions for this assay. Please let us know how you
get along if you do try this method.
UPDATE: 8/21/05. The factor for distilled spirits
will vary dependent upon the sugar (carbohydrate) content of
the spirit. The value is also alcohol-strength dependent and
rises with increasing alcohol (volume) content. For
approx 40% by volume spirits (without any carbohydrate) we
are finding factor values of 1.240 to 1.257 - depending upon
the type of spirit. [Vodka is around the 1.240 mark.] A
value of 1.25 would be a good compromise for most other
spirits at or about 40% by volume content (with very little
to no carbohydrates) - though we AGAIN stress that these are
only for non-official rough estimates for alcohol content.
Experiment and work out the factors for your favorite spirit
and get values checked by officially accepted methods for
appropriate labeling and usage purposes. We cannot be
held responsible for your reporting alcohol contents to any
persons or bodies and authorities based on our factors
presented here.
As discussed
above this method will only give unofficial values for
alcohol content.
Need a Periodic
Table for your calculations? Click the Thumbnail image
below for a full-sized Table. [Once opened you can further
expand to the extent that your Browser will allow].
|
