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confounded with the bitter, preservative resins) possesses in a 

 marked degree the aroma of the oil itself, and is slightly soluble in 

 the boiling wort, and not, of course, volatile with the steam. To 

 this is chiefly due the hop flavour communicated to the wort during 

 boiling, but some experiments which I have made render it not 

 improbable that there are also present in the hop cones solid, non- 

 volatile substances which have their share in the communication of 

 flavour. Of course, in the process of dry hopping, the oil plays a 

 more obvious part, a little of it passing directly into solution in the 

 beer. It may be added that the resinification of the oil is somewhat 

 retarded, but not prevented, by cold storage, being much more 

 dependent on the presence or absence of air. Formerly it was 

 asserted that hops owed their preservative property to the essential 

 oil, but this is now known to be largely, if not entirely, resident in 

 the so-called " soft resins." A few years ago, in conjunction with 

 Mr. H. E. BURGESS, I made a number of experiments on this 

 point, using malt wort, beef-extract solution and beer as nutrient 

 media, and we found that neither the oil itself nor any of its 

 separated constituents exerted any appreciable inhibitory action on 

 the growth of any of those bacteria which are chiefly responsible for 

 disease changes in beer. 



The Oxidation of the Oil. The well known " cheesy " odour 

 which most hops develop on storage, has been almost invariably 

 stated to be due to the production of valeric acid from the oil by 

 oxidation. In 1883, OSSIPOW investigated the action of certain 

 chemical oxidising agents on the oil, and identified isovaleric acid 

 among the acid products of the reactions ; whilst WAGNER thirty 

 years before had expressed his opinion that this acid was derived 

 from one of the oxygenated constituents of the oil. 



It may be at once said that valeric acid is never formed as a 

 product of the aerial oxidation of hop oil, for the author has in his 

 possession numerous samples of oil which have been exposed to the 

 air for years, and whilst they have become more viscous, or in some 

 cases completely resinised, no trace of valeric acid, judging from the 

 smell, has been produced in any instance. As has been pointed out 

 above, the oil contains linalyl isononoate, and possibly a little of 



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