Craft Brewers Now Have a New Tool for Sniffing Out Trace Flavor Compounds
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Craft brewers now have a new tool for sniffing out trace flavor compounds:
Craft-beer aficionados relish the endless flavor variations that can be achieved by mixing and matching different varieties of hops, whether one favors refreshing citrus or fruity notes or something a bit more earthy or pine-scented. But some of the chemical compounds that contribute to those flavors are present in such trace amounts that it's difficult for brewers to measure and track them during the brewing process. Now German scientists have devised an automated, efficient method for doing just that, according to a recent paper published in the Journal of Agricultural and Food Chemistry.
As we've previously reported, all beer contains hops, a key flavoring agent that also imparts useful antimicrobial properties. (Without them, beer spoils quickly.) Brewers mash and steep grain in hot water, which converts all that starch into sugars. This is traditionally the stage when hops are added to the liquid extract (wort) and boiled to give the beer that hint of bitterness. During the boiling process, a certain portion of the resins (alpha acids) in hops isomerize into iso-alpha acids. That chemical rearrangement of the molecules is what produces bitterness. Yeast is then added to trigger fermentation, turning the sugars into alcohol.
But a little hops goes a long way. Add too many hops, and the beer will be so bitter as to be undrinkable.
[...] Rettberg and his co-authors noted that thiols also contribute to the distinct aromas of wines like Sauvignon Blanc, and they were able to draw on a rich array of prior research in viticulture and oenology. Specifically, they adapted a method for measuring wine thiols involving coated polymers placed into the air above a wine sample, thereby converting any aerosolized wine thiols into compounds that can be more easily measured. The method was still insufficient to detect the trace amounts of thiols in beer, so Rettberg et al. combined it with gas chromatography-tandem mass spectrometry to reach the necessary sensitivity.
Journal References:
1.) Johanna Dennenlohr, Sarah Thorner, Nils Rettberg. Analysis of Hop-Derived Thiols in Beer Using On-Fiber Derivatization in Combination with HS-SPME and GC-MS/MS, Journal of Agricultural and Food Chemistry (DOI: 10.1021/acs.jafc.0c06305)
2.) JuhaMatti Pihlava, Tuula Kurtelius, Timo Hurme. Total hordatine content in different types of beers, Journal of the Institute of Brewing (DOI: 10.1002/jib.311)
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