|Chromatography is a method of separating and analyzing mixtures of chemical components.It is used by large
brewery laboratories to identify and quantify volatile and non- volatile beer components. Separation occurs by
allowing a mixture to travel through an adsorbent matrix so that each compound is ultimately resolved into
separate zones based on chemical or physical properties such as polarity, boiling point, or size.
The simplest forms of chromatography include separation on paper sheets or specially coated plates or through
columns packed with an inert media. Various methods are then employed to detect and identify the different
resolved species. Two sophisticated methods of chromatography are gas chromatography (GC) and high
performance liquid chromatography (HPLC). Both provide separation techniques for qualitative or quantitative
identification of substances.
Gas chromatography relies on selective adsorption and release (desorption) of volatile components on a
stationary phase. Components in a mixture are carried through a column by an inert gas to a specific type of
detector where species, via calibration with known compounds, are identified based on retention (residency) time
in or on the column.
In the brewery laboratories, GC is used to separate higher alcohols and esters in beer and phenols and things
such as the buttery flavored diacetyl compound. Results are related back to the chemical composition of the beer
and to its sensory properties. GC results can be used to give early warning of an infection (which may produce
diacetyl above normal levels) or simply to provide a “map” of a beer’s aromatic properties.
In some breweries, GC results are used to determine when a beer is ready to leave its fermenter and be put
into a lagering cellar for aging; the decision would depend on diacetyl having dropped into an acceptable
range of concentration
Barley Harvest is the cutting, threshing, separating, and cleaning of individual barley grains from the
mature barley plant. Depending upon variety and climate conditions, barley grows from 12 to 48 inches tall. The
tightly packed spikes or ears of seed kernels can take from 40 to 55 days to fully ripen after flowering and droop
down when ready to harvest. Growers closely monitor and test mature plants for grain size, protein content,
and moisture. For malting barley, the moisture content at harvest tends to be between 12% and 17%,
whereby 12.5% is considered ideal.
Harvesting by “direct head cutting” involves cutting the ripened ears off close to the stem, high on the plant, to
minimize debris. The crop is then threshed to separate the individual grains from other plant material and
cleaned of foreign matter. Swathing, by contrast, involves cutting the plant low, leaving a short bed of stubble
that supports the long interlaced stems and ears off the ground, where the crop is allowed to dry in the field
before being gathered and threshed.
Excessive handling, however, can break, crack, or abrade the barley kernel, rendering it useless to the
malt house and brewer. Dry grain, properly stored, will last for months or even years.
Hope you found this month's column of interest. If you have any questions about beer or brewing
or just want to submit a word for me to discuss here just e-mail it to me.
Thanks and Cheers!
|Chromatography // Barley Harvest
|A new column by
|Jack O'Reilly attended the
famous Siebel Institute/ World
Brewing Academy in Chicago.
|I'm very excited to be part of the BeerNexus team. I think my many years in the
beer business both as a brewer and manger will enable me to explain and
investigate many topics of interest for those who really love craft beer.
Hope you join me every month.
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|Techniques and insights
for the serious ceft beer
fan and home brewer.