RECENT WORK IN AGRICULTURAL SCIENCE. 



AGRICULTimAL CHEMISTRY— AGROTECHNY. 



A study of the soft resins in sulphured and unsulphured hops in cold and 

 in open storage, G. A. Russell {U. S. Dept. Agr. Bui. 282 (1915), pp. 19, 

 figs. 10). — The commercial value of hops is almost entirely contingent upon two 

 considerations, viz, the nature and quantity of the soft resins and the aroma. 

 In order to get additional data (E. S. R., 29, p. 13) regarding the effect of vari- 

 ous storage conditions upon the soft resins of sulphured and unsulphured hops, 

 a quantity of material obtained from Perkins, Cal., was prepared and held under 

 observation for several years. 



"Although sulphuring and cold storage are efficient factors in retarding the 

 diminution of the quantity of soft resins in hops, they do not prevent chemical 

 changes from taking place therein. Nevertheless, the data obtained by the study 

 of these changes indicate that they are influenced to a considerable degree by 

 both sulphuring and cold storage. . . . 



" Determinations were made of the moisture, the percentage of soft resins, 

 hard resins, and total resins, of the color, odor, and taste of the soft resins, and 

 of the acid, ester, saponification, and iodin values of the soft resins. The mois- 

 ture content in the sulphured and unsulphured hops held in cold storage in- 

 creased during the first year and then remained practically constant in all the 

 samples throughout the period of storage. The moisture content of the sul- 

 phured and unsulphured hops in open storage varied from year to year, accord- 

 ing to existing weather conditions. 



" The percentage of soft resins in all the samples decreased with each year 

 of storage, becoming very pronounced In the third year. The percentage of hard 

 resins in all the samples increased with each year of storage, approaching a 

 uniform figure at the close of the third year. Both sulphuring and cold storage 

 retarded the decrease in the percentage of soft resins and increased the per- 

 centage of hard resins. A combination of the two factors was more effective 

 in retarding these changes than either factor alone. 



" The percentage of total resins in all the samples varied from year to year, 

 and in the third year it became materially less than that of the original sample. 

 The low total is probably due to the formation of products insoluble in the sol- 

 vents used. 



"The color, odor, and taste of the soft resins are of very little value in de- 

 termining quality and are not indicative of any changes that may have taken 

 place therein. 



" The acid value in general decreased in the sulphured hops in cold and in 

 open storage, and increased in the unsulphured hops in cold and in open storage. 

 Sulphuring apparently retards the formation of free acids, and a combination 

 of sulphuring and cold storage is most effective in retarding changes in free 

 acidity. 



" The ester value in general increased in all the samples of hops. Sulphuring 

 apparently favors the formation of esters, and this factor in combination with 



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