Nuclear physics and the fight against beer fraud

GO INTO a trendy pub and the beer list will be accompanied by tasting notes as purple as in any upmarket wine bar. The “grassy aromas” and “citrus notes” come from the flowers of Humulus lupulus, or the hop plant. These vary in flavour from region to region and between different varieties of the plant. Brewers therefore tend to be rather particular about obtaining specific types of hops from specific plants in specific places, to ensure the flavour of their beer does not change unpredictably.

But they cannot always be sure of what they are buying. Unscrupulous growers can adulterate high-quality hops with cheaper varieties, which can affect a beer’s taste. Detecting doctored shipments can be difficult. Existing tests focus on measuring levels of chemical telltales such as essential oils. But they are not very sensitive, typically requiring adulteration of 10% or more before triggering an alert. Now, as they report in the Journal of Agricultural and Food Chemistry, Miha Ocvirk, a PhD student at the Institute of Hop Research and Brewing in Slovenia, and Iztok Kosir, his supervisor, think they have a better idea.