22 



Twenty-second Convention, 1905, Bui. 99, Cir. 26. 



PROVISIONAL METHOD FOR THE SEPARATION OF NITROGENOUS BODIES IN BARLEY AND 



MALT. 



[Condensed description of the method as given by H. T. Brown, in the "Transactions of the Guin- 

 ness Research Laboratory," 1903, I (1): 61, for The Estimation in Barley and Malt of the Total 

 Amount of Nitrogenous Substances Soluble in Water.] 



In order to have the results on the barley and on the malt comparable, the percentage 

 results obtained on the malt are converted back to the equivalent weight of its original 

 barley. To do this, it is necessary to know the weight of 1,000 kernels of dry barley and of 

 1,000 kernels of dry malt. This weight of dry barley being expressed by Wb and of dry 

 malt by Wm, any percentage weight of a constituent in the dry malt is converted back to 



its original barley by multiplying by the factor ^r' 



It was found that the relation of the weight of grain to that of the extraction water was a 

 very important factor, owing to the different solubility of globulins in salt solutions of 

 varying strength, and in order to make this constant the following conditions were estab- 

 lished: 



The weight of barley and of malt taken was such that when the solution was made to 

 its final volume it contained the extract and insoluble portions of amounts corresponding 

 exactly to 20 grams of dry barley in 100 cc. For the extraction 75 per cent of the required 

 amount of water was taken at first, the mixture shaken in a revolving shaker for a definite 

 time, the flask then filled to the required volume, and after thorough mixing allowed to 

 stand for six hours, measuring the time from the beginning of the shaking. It was found 

 that six hours' extraction removed all of the nitrogenous substances soluble in cold water 

 and that any decided increase in the length of time of extraction was liable to introduce 

 errors due to the action of proteolytic enzymes. 



In order to obtain, by calculation, the amount of malt, which, in the final volume of the 

 mixture of malt and water, shall contain in 100 cc the exact equivalent of 20 grams of dry 

 barley, the moisture content of both barley and malt must be known; also the relation of 

 the dry weight of 1,000 kernels of barley to that of the resulting malt. Knowing these 

 factors, the following general formula is obtained: 



Wm.C.V 



Wb (100-Mm) 

 in which 



X weight of air-dry malt to be taken. 

 Wm = weight of 1,000 kernels of dry malt. 

 Wb = weight of 1,000 kernels of dry barley. 

 Mm = percentage of moisture in air-dry malt. 



C= required concentration in terms of grams of dry barley per 100 cc of the final 



mixture. 



V = volume of final mixture in cubic centimeters. 



After the extraction is completed the contents of the flask is filtered and definite volumes 

 (100 cc) of the clear filtrate taken. In one of these portions the amount of nitrogen is 

 determined by the Kjeldahl method. This represents the total soluble nitrogenous com- 

 pounds. The other portion of the filtrate is boiled down to small bulk, in a beaker, again 

 made up to its original volume and filtered. The nitrogen in this filtrate represents the 

 soluble nitrogenous compounds not coagulable by boiling, and the difference between this 

 and the total nitrogen is the nitrogen representing the nitrogenous substances coagulable 

 by boiling. 



