266 BOTANY OF CROP PLANTS 



hop is probably the alkaloid, lupuline. Of the r esins in the 

 lupulin glands, two principal ones have been identified, a hard 

 and a soft resin. The hard resin has a slight bitter taste and 

 little or no antiseptic power in the beer wort. The soft 

 resins are much more bitter, imparting this taste to the beer 

 wort; they also'prevent the growth of bacteria in the wort 

 and thus have a preservative effect. The total resin content 

 of hops varies from lo to i8 per cent. Hop tannin makes 

 up about 4 to 5 per cent, of the hop. It is thought by some 

 that it serves to precipitate the albuminous material from 

 beer wort. 



Uses of Hops. — In some European locaHties, young hop 

 sprouts are used as an early spring vegetable. The most 

 tender sprouts are those which have been covered with soil 

 during the winter. 



Before the days of yeast cakes, yeast for bread-making was 

 made by cultivating wild yeast in a decoction of hops and 

 water. Some of the material obtained was mixed with the 

 dough. The various constituents extracted from the hops 

 add flavor to the bread, and also have antiseptic properties. 



The most important use of hops, however, is in the brewing 

 process. Preparatory to their use in the breweries, the hops 

 are taken through a curing process in which they are kiln- 

 dried, and then subjected to the fumes of burning sulphur. 

 ''Sulphuring" bleaches the hops, and acts as a preservative. 

 After the sweet beer wort is made in the brewing process, it 

 is boiled with hops. In this process, among other effects, 

 the flavor of the wort is improved by the extraction of the 

 active ingredients in the hops. The essential oil of the lupu- 

 Hn glands imparts an aroma to the beer, the non-resinous 

 bitter principle and the resins give to the hopped wort a shghtly 

 bitter taste, and the tannin probably serves to precipitate 

 albuminous substances. Moreover, the maHc and citric 



