White Labs adds new GC testing options
By Ryan Craig
White Labs Microbiologist
We have been using the White Labs GC (gas
chromatograph machine) more and more recently, and now we are adding
more esters and fusel alcohols to the testing options.
In addition to our Ethanol and VDK analyses, which
some of you might have been introduced to during our big QC Day, we are
now capable of analyzing Acetaldehyde, Ethyl Acetate, Isoamyl Alcohol,
and a few other esters and fusel alcohols.
Some basic results from these new analyses can be
seen in Neva Parkerís recent Zymurgy article, which details how
fermentation changes such as different temperatures can affect yeast
fermentation specific flavors. Some of these new analyses might also
join our Big QC Day line up of tests in the future.
These compounds are a few of the ones that are
produced above the lower limit of our GC detector. They are some of the
more flavor-active compounds, so they are important flavor-wise. Here is
some more information about these compounds:
Acetaldehyde is basically a precursor of Ethanol,
it has a green apple aroma and flavor. It is believed to be one of the
causes of beers going stale and tasting like cardboard, and it is also
believed to cause hangovers.
Ethyl Acetate is probably the biggest flavor
compound that yeast produce, it can account for up to a third of all
esters. At lower levels it has a fruity aroma and taste, at higher
levels its aroma and taste is like nail-polish remover.
Isoamyl Alcohol is a
fusel alcohol that is produced around its flavor threshold.
When conducted together, these tests can paint an
interesting picture of what flavors your yeast is adding to your beer.
Nevaís article dealt with minor things such as temperature changes, and
different yeast strains, and she showed that minor changes can have a
pretty significant impact on your beerís flavor; the blind taste test
with these beers was really interesting when compared to the numbers.
Other than understanding what your yeast is adding to
your beer, these tests are good to have as part of your QC program. If
you are doing everything the same, you should be seeing the same
We will run these tests on our own yeast strains;
this will give us a greater understanding of what these strains
contribute to beer beyond what we learn from brewers by word of mouth.
We also expect to conduct these tests for other laboratories without the
knowledge or equipment that we possess.
Flavor is a pretty complicated thing, as anyone who
is involved in brewing knows. These tests over time will help us
understand flavor a little better.
Craig, a microbiologist for White Labs, spends part of his workday
operating the GC machine.