PBESEEVATION AND STORAGE. 275 



process remains unaltered, another portion being oxidised 

 into sulphuric acid, whilst a third portion enters into 

 unstable combination with some, as yet undefined, con- 

 stituents of the hop (Behrens). 



Numerous experiments have demonstrated the great 

 importance of the temperature of the storage chamber on 

 the preservation of hops. G. Barth has published a very- 

 interesting paper on the proper method of storing hops,^ and 

 arrived at the conclusion that cold is the best means of 

 minimising all the chemical and physical processes calcu- 

 lated to give rise to change in hops during prolonged storage. 

 Given low temperature and a low content of moisture, the 

 influence of micro-organisms is greatly circumscribed ; and, 

 moreover, the chemical modification of the hop resins will 

 be unimportant, since the lower the temperature the more 

 gradually do chemical reactions proceed. The effects of 

 cold will also be greatly supplemented by excluding atmos- 

 pheric air, as far as possible, from, the chamber. 



Barth refers to the circumstance that several large 

 English hop merchants have successfully employed cold 

 storage for hops, a practice also followed, at an earlier date, 

 in America. Messrs. Cattley, Gridley & Co., of London, cool 

 their store-rooms down to - 5° C. by the aid of refrigerators ; 

 and it is claimed that hops kept in this manner are indis- 

 tinguishable from new hops in freshness, aroma, colour and 

 brewing value. 



Other merchants content themselves with reducing the 

 temperature to 2° to 3° C. 



Dr. Issleib,^ Adams,^ and others proposed storing pressed 

 hops in air-tight chambers charged with carbonic acid gas at 

 a temperature only a few degrees above zero C, this gas being 

 inert and therefore uninjurious to the hops, whilst prevent- 



1 ZeitscTwift fll/r das gesaimmte Bravmjesen, 1898, No. 44. 



2 Ibid., 1892. 3 ii)id_^ 1894. 



