Providing a quality chemical analysis service for regional hop growers and craft beer brewers in the Midwest.
Our ASBC Hop Testing Methods
Midwest Hop and Beer Analysis, LLC, is proud to be a Corporate Member of the American Society of Brewing Chemists (ASBC). We are committed to following the testing protocols developed by both the (ASBC) and the European Brewing Convention (EBC). Both organizations cooperate to establish National and International standards in the Brewing Industry.
Moisture Content by Distillation
ASBC Hop-4A (Distillation Method)
Distillation is recognized by the ASBC as
the most accurate method of determining the actual moisture content.
However, it is a time consuming process that involves boiling a precisely measured
sample of hops in an organic solvent like purified methylcyclohexane. The water and
solvent vapors are cooled, returning them to their liquid form. As they trickle
back toward the boiling-flask, the moisture is retained in a catch-tube. The system
requires careful calibration, but can return consistent and reliable results.
Moisture Content by Forced-Air Drying Cabinet
ASBC Hops-4C (Routine Air Oven Method)
Oven drying is a more practical approach in which a moisture-containing sample is
carefully weighed and then dried in an oven with a forced air flow and carefully
regulated temperatures. The sample is reweighed after drying and the lost mass is
assumed to be due to the evaporated moisture. However, typical oven temperatures (over
170 degrees F) drive off some of the essential oils, as well as the moisture, leading
to inescapable errors. We use a low temperature (below 110 degrees F) dehydrating
system, designed specifically for this one purpose, and calibrated by referencing
results from distillation tests.
Alpha Acids and Beta Acids Content by UV Spectroscopy
ASBC Hops-6A (by solvent extraction and
This method accurately reports the total amount of the α-acids and β-acids present, but does not provide specific information on the identities or relative amounts of the individual acids (e.g., humulone, cohumulone and adhumulone). We feel that knowledge of the amounts of specific α-acids in a sample are of less importance to the brewer than the actual perceived bitterness. If you are at all concerned about the bitterness characteristics of your hops, then, by all means, make a tea of them and taste it!
This is the original ASBC solvent extraction method
established as the standard in 1970 and revised in 2008. The hops (wet or dry, whole
or processed) to be tested are carefully weighed and coarsely ground. An ultra-pure
organic solvent (toluene) is added to the sample and agitated to dissolve the alpha-
and beta-acids. The solution, now containing a variety of compounds, is separated
from the solid hop residue and further treated to prepare it for spectrometry. The
final solution, containing the diluted extracts of alpha and beta acids, is placed
in a calibrated ultraviolet (UV) spectrophotometer. The amount of UV light absorbed
by the solution at three specific wavelengths indicate the amount of alpha acids and
beta acids present in the solution. Knowing the weight of the hop sample and the
volumes of the various solvents added allows one to determine the amount of the
bittering acids in the original sample.
Hop Storage Index (HSI)
ASBC Hops-12 (by solvent extraction and
This measurement relies on the same solvent extraction and spectrophotometry process used (and described) above, though it depends on a slightly different mathematical analysis. For this reason, the results of the HSI analysis is included as part of the previous test.
As the hops "age" with exposure to time, heat and oxygen, the α-acids
are converted into a variety of unflavored and off-flavored compounds, collectively
referred to as "oxidized α-acids". As the oxidation takes place, the
absorbance of UV light at the wavelength corresponding to the α-acids decreases,
while the absorbance at the wavelength corresponding to the oxidized α-acids
increases. The ratio of one absorbance value to the other gives a unit-less number
known as the Hop Storage Index. HSI values run from a low of about 0.24 to a high of
about 2.5. On this scale, lower numbers are "good" and higher numbers are
Total Essential Oil Content by Steam Distillation
ASBC Hop-13 (by steam distillation)
This method accurately reports the total amount of all essential oils present, but does not provide specific information on the identities or relative amounts of the individual essential oils. We feel that knowledge of the amounts of specific oils in a sample is of less importance to the brewer than the actual perceived aroma and taste. If you are at all concerned about the flavor of your finishing hops, then, by all means, taste them!
A large, carefully weighed sample of hops is placed in a large water-filled vessel and
brought to a steady boil. Steam from the boiling water and vapors from the essential oils
are cooled in a chilled condensing column and return to their liquid forms. As they
trickle back toward the boiling-flask, the liquid essential oils are retained in a
syphon-like catch-tube. The system requires careful calibration, but can return
consistent and reliable results.