280 



HOPS. 



Well-dried hops contain 8 to 12 per cent, of moisture, 

 and a larger proportion must be looked upon as suspicious, 

 at least. 



Hop oil- — The content of the ethereal oil varies from 0"2 



to 0'8 per cent. This oil which, according to its quality, 



imparts a more or less agreeable odour to the hop, is con- 



, tained in the lupulin granules, and, being volatile, can be 



recovered therefrom by distillation with steam. 



Thus, if the hops be placed in water and heated, and 

 the condensed vapours collected in a receiver, the hop-oil 

 will be found floating as a pale-yellow film on the surface 

 of the accompanying water. The oil in the glands is united 

 with the resinous bodies in the form of a soft resin or balsam 

 (Thausing^). At 15° C. this bitter oil has the specific gravity 

 0'8751 ; it is readily soluble in ether, less so in alcohol, and but 

 very sparingly so in water, 20,000 parts of which, according 

 to Chapman, are required to dissolve 1 part of the oil. It is 

 volatile, not only at boiling heat but also at the ordinary 

 temperature, and it boils at 150° C. Although beer wort 

 only takes up a very small quantity of the oil during the 

 process of hopping, it is, nevertheless, this substance which 



' Thausing, Die Theorie und Praxis der Mahbereitung und Bierfabrication, 

 Leipzig, 1898. 



