Commercial scale extraction of alpha-acids and hop oils with compressed CO2

By the end of the 19th century, the dual properties of the flavour and preservative value of hops had become the subjects of investigation by chemists. In the 1880s the effect of the hop resins on beer spoilage bacteria had been demonstrated [1, 2] and later their influence on some pathogenic organisms [3]. The resin fractions designated alpha and beta were separated and their bactericidal activities compared [4]. For a while, the resin content of a hop was used as an indication of preservative value (P.V.). It was found that the resins contained the bitter principles while the aroma was predominantly due to the essential (volatile) oil.