94 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



specific gravity instead of parts per thousand. It has been adopted by the English 

 excise. 



The metho.d outlined above was employed by the same authors, except that they 

 determined the specific gravity of the dealcoholized beer, directly on the residue 

 from the alcohol determination after diluting to the volume of beer employed. 



6. DETERMINATION OF THE DEGREE OF FERMENTATION. 



Calculate from the formula 



jy_ 100 sp 



G 



in which D is the degree of fermentation, sp the specific gravity of the dealcoholized 

 beer, and G the gravity of the original wort. 



7. DETERMINATION OF TOTAL ACIDS. 



Heat 20 cc of the sample to incipient boiling to liberate carbon dioxid, and titrate 

 with decinormal sodium hydroxid, using neutral litmus paper as indicator. Each 

 cubic centimeter of decinormal alkali employed is equivalent to 0.009 grams of lactic 

 acid. The number of cubic centimeters of decinormal alkali employed in titrating 

 20 cc of beer is multiplied by 0.045 for the acidity expressed as grams of lactic acid 



per 100 cc. 



8. DETERMINATION OF VOLATILE ACIDS. 



Follow the directions given for the determination of volatile acids in wine (p. 84) . 

 This determination is rarely of value in sound beer. 



9. DETERMINATION OF REDUCING SUGAR. 



Proceed as directed on page 85, but boil four minutes instead of two. Express 

 the result in terms of maltose equivalent to copper reduced, according to Table IX. 



10. DETERMINATION OF DEXTRIN. 



Deduct from the extract the sum of the maltose, protein, glycerol, total acids, and 

 ash. While this method is only approximate, it is sufficiently accurate for most 

 purposes. 



If a more accurate determination is desired, 50 cc may be treated by Sachsse's 

 method for the hydrolization of starch, and dextrose determined by copper reduc- 

 tion, according to Allihn's method. From the amount of dextrose so found, 95 per 

 cent of the amount of maltose present in the beer is deducted (20 parts maltose are 

 equivalent to 19 parts dextrose) and the remainder multiplied by 0.9. 



11. DETERMINATION OF GLYCEROL. 



Proceed as directed on page 82. The milk of lime is added during evaporation 

 after the carbon dioxid has been expelled. 



12. DETERMINATION OF ASH. 



Evaporate 25 cc to dryness, ignite as directed on page 83, and weigh. 

 13. DETERMINATION OF PHOSPHORIC ACID. 



Employ the official gravimetric or volumetric method, using the residue obtained 

 in the determination of ash. 



14. DETERMINATION OF PROTEIN. 



Employ the Kjeldahl or the Gunning method for the determination of nitrogen, 

 and multiply the result by 6.25. 



U. S. Dept. of Agr., Div. of Chem., Bui. 46, p. 13. 



