77. The chemical fingerprint of
beer from a single experiment with minimum sample preparation—A rapid
quantitive molecular analysis by 1H NMR spectroscopy
John Edwards (1); (1) Process NMR Associates, Danbury, CT, U.S.A.
Analytical
Poster
1H nuclear magnetic resonance spectroscopy (NMR) has been used by
chemists for 50 years as the ultimate tool for molecular structure
elucidation. Another area where NMR spectroscopy excels is the
quantitative analysis of complex mixtures where multiple individual
molecular components produce NMR signals that can be identified and
quantified to produce a chemical fingerprint that is useful for i)
evaluating incoming raw materials; ii) following mash, sour mash, and
sparging chemistry; iii) following the progress of fermentations; iv)
following the appearance of undesirable components; and v) observing the
chemistry changes during barrel and bottle aging processes. In a single
NMR spectrum it is possible to observe in one experiment, in 175 µL of
sample, with little to no sample preparation, a wide range of chemical
components such as alcohols (ethanol, methanol, 1-propanol, isobutanol,
iospentanol), organic acids (lactic, acetic, pyruvic, succinic, citric,
malic, tartaric), esters (ethyl acetate and ethyl lactate), amino acids
(alanine, GABA, valine, proline, arginine, tryptophan, phenylalanine,
tyrosine, histamine), and detailed residual malt and carbohydrate
chemistry (glucose, fructose, sucrose, lactose, alpha(1-4)- and
alpha(1-6)-glucans, and more) as well as adjunct components from
additions of coffee or cocoa (caffeine and theobromine). The chemical
fingerprint is extremely detailed and allows brewers to determine what
is happening within their brew from the mash to the bottle. The NMR
technique, though excellent for providing detailed information down to a
few ppm of the various components does not observe hop chemistry
present in the finished beers, as the concentration is below the limit
of detection of the analysis. The technique is particularly useful for
following sour beer processes.
John Edwards received a B.S. degree in chemistry from Durham
University in Durham, U.K., in 1986 and then a Ph.D. degree in physical
chemistry from the University of South Carolina in Columbia, SC, in
1990, specializing in NMR spectroscopy. He spent seven years working for
Texaco Research running the NMR facility and then started his own
analytical NMR service and consulting business, where he utilizes NMR to
support several hundred industrial and academic customers. For the past
18 years he has developed quantitative approaches for the analysis of
pure materials, as well as complex mixtures such as beer, wine, cider,
and herbal supplements. He is currently collaborating with several
breweries on developing a deeper understanding of where detailed
chemical fingerprint information can assist brewers in their brewing
process and in their quest to produce consistent products.
