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. Bu...