16 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



12. DETECTION OF PRESERVATIVES. 



The chemical preservatives commonly used with meat products are borax and 

 boric acid and sulphites. Salicylic and benzoic acids are occasionally used, and 

 formaldehyde is said to be used, although the writer has failed to detect- its presence 

 in meat preparations. The general methods for the detection of these preservatives 

 are given on pages 107 and 110. A few special methods are described below. In gen- 

 eral, preservatives may be separated from meat by digesting a few minutes in warm 

 water, made slightly acid or slightly alkaline according as the nature of the pre- 

 servative is basic or acid. 



(a) BORAX AND BORIC ACID. 



If present in noticeable amounts, boric acid may be detected in meat products by 

 heating 20 grams of the sample a few minutes in about 100 cc water acidified with 6 

 or 8 cc of concentrated hydrochloric acid and testing with turmeric paper as directed 

 on page 110. If no action is obtained by this method, about 20 grams of the sample 

 should be made alkaline with calcium hydroxid, ignited, and the ash tested as 

 directed under preservatives. 



(b) SULPHUROUS ACID. 



The distillation method for the detection of sulphurous acid (see page 107) will 

 answer for the examination of meat, but mere traces should be ignored. According 

 to Ostertag, a the microscopic examination of meat that has been preserved with 

 sodium or calcium sulphite often discloses the presence of crystals of sodium or 

 calcium sulphate, due to partial oxidation of the sulphite. 



In the absence of chlorids and nitrates Kiimmerer a employs potassium iodate 

 paper in the following manner: Place the sample of meat on potassium iodate paper 

 and moisten it with dilute sulphuric acid (1:8) free from oxids of nitrogen. In the 

 presence of even minute traces of sulphites a deep-blue color is immediately formed, 

 while in the absence of sulphites only a faint-blue color is produced, and that after a 

 considerable time. This method is of limited application, since it can not be used 

 with meats containing salt or saltpeter. 



13. DETECTION OF COLORING MATTER. 1 * 



Sausages and other preparations in which chopped meat is employed rapidly 

 become discolored on exposure to the air. This change does not take place to a 

 marked extent with meat that has been cured in a pickle containing saltpeter. With 

 fresh chopped meat, and sometimes with corned meat, especially that cured without 

 saltpeter, coloring matter is sometimes added to prevent the change of color which 

 would naturally take place. Aniline dyea and cochineal carmine are ordinarily 

 employed for this purpose, though in some instances vegetable colors have been 

 detected in the form of lakes. The coloring matter may often be extracted by heat- 

 ing for 15 or 20 minutes with 50 per cent alcohol, 50 per cent glycerin slightly acidi- 

 fied, a mixture of alcohol and glycerin, c ammonium hydroxid, or a 5 per cent solu- 

 tion of sodium salicylate d in water. Approximately equal weights of meat and 

 solvent may be used. 



In case the filtered extract by any of these methods is colored red or deep yellow, 

 it should be evaporated nearly to dryness, slightly acidified with hydrochloric acid, 

 and boiled a few minutes after the addition of a thread of fat free wool. If the wool 

 is dyed, it may be examined as directed by the referee on coloring, matter. If the 

 wool is not dyed, the solution is examined spectroscopically. 



Handbuch der Fleischbeschau, 3 ed., p. 826. 

 > See appendix, p. 149. 



Klinger and Bujard, Ztschr. ang. Chem., 1891, 515. 

 * Spaeth, Pharm. Centralh., 1897, 38, 884. 



