The enrichment of beer hoppy flavour with hop oil recovered from kettle exhaust.

Kowaka, M., Sakuma, S., Nakayama, K. and Totsuka, T.

Abstract
Laboratory scale experiments were carried out to discover the optimum conditions (scrubbing solutions, absorbents, solvents etc.), for recovering hop oil from the vapour of boiling hopped wort. The results of these trials were used to devise a scheme for recovering hop oil from equipment used in the brewery to reduce the odour of vapour escaping from the kettle exhaust. This vapour is condensed to remove high boiling point aromatic compounds and scrubbed in a spray tower, first with water, then with 0.1% sodium hypochlorite solution. This removes substances such as pyrazine and pyrazole. The exhaust is then passed through activated charcoal. Hop oil (1.05 kg) was recovered from this activated charcoal (30 kg) by extracting with methylene chloride on the pilot scale. Recovery was 3.5%. G.L.C. analysis showed that its composition was similar to that of the original commercial product. The hop oil had a distinct worty aroma which came through when it was added to beer, but when added to wort at 5-10 ppm the final beer exhibited a sound hoppy flavour and the worty odour could not be detected. This process can be used to recover hop oil economically from kettle exhaust for use by the brewing industry.
Keywords : beer enrichment flavour hops oil vapour