12 PROVISIONAL METHODS FOR ANALYSIS OF FOODS. 



and wash with hot water, being careful that the temperature of the solution and wash 

 water shall not be less than 90 C. at any time. 



Transfer the filter papers containing the tannic acid and phospho-tungstic acid 

 precipitates to a Kjeldahl flask and determine nitrogen. The nitrogen so obtained 

 multiplied by 6.25 gives the percentage of proteoses, peptones, and gelatin. 



(f) DETERMINATION OF MEAT BASES. 



Deduct from the total nitrogen the sum of the nitrogen obtained in the determina- 

 tion of coagulated proteids, connective tissue, globulin, and proteoses, peptones, and 

 gelatin for the nitrogen of meat bases. Multiply the result by 3.12 for the percentage 

 of meat bases. a 



8. DETERMINATION OF STARCH (FOR CHOPPED MEAT, SAUSAGE, DEVILED MEAT, ETC.). 

 (a) QUALITATIVE DETERMINATION. 



Treat 5 or 6 grams of the sample with boiling water for two or three minutes; 

 cool the mixture, and test the supernatant liquid with iodin solution. In using this 

 test it must be remembered that a small amount of starch may be present as the 

 result of the use of spices. If a marked reaction is given, however, it may be con- 

 cluded that starch or flour has been added, and a quantitative determination may be 

 made. The above qualitative method may be replaced by a microscopic examina- 

 tion, by which not only the presence of added starch, but also the variety employed, 

 may be determined. 



(b) QUANTITATIVE DETERMINATION. 



The official methods of the association for the determination of starch will not 

 answer for the examination of meat because of the presence in meat of bodies which 

 hold a portion of the cuprous oxid in solution, and thus give results which are too 

 low. In this laboratory Munson examined a series of sausages which contained no 

 starchy material except the spices employed in their manufacture. He obtained less 

 reduced copper from the sausages than from the blank determination of reducing 

 bodies in the malt infusion employed. 



(1) Ambuhl's method.* 



This method has been adopted by Swiss authorities. It is short and convenient, 

 although the results obtained by it are only roughly approximate. 



Thoroughly macerate 2 grams c of the meat under examination with fifty times its 

 weight of water. Boil for thirty minutes and dilute to 100 cc for every gram of meat 

 employed. Cool an aliquot portion of the liquid, treat with iodin, and compare the 

 depth of color with solutions containing a known amount of the same kind of starch 

 (the variety of starch in the sample is determined microscopically), and boiled for 

 the same length of time. 



(2) Mayrhofer's method, d modified by Bigelow. e 



Treat from 10 to 20 grams of the sample under examination (depending upon the 

 amount of starch indicated by the iodin reaction) in a porcelain dish or casserole 

 witfc 50 cc of an 8 per cent solution of potassium hydroxid and heat the mixture on 

 the water bath until the meat is entirely dissolved. The operation may be hastened 

 by macerating the larger pieces with a glass rod. Add an equal volume of 95 per 



See appendix, p. 149. 



I'Pharm. Centralh., 1881, 22, 438; Abstract Ztschr. anal. Chem., 1882, 21, 486. 



Ambuhl directs that from 2 to 10 grains be employed, according to the size of the meat particles. 

 If the sample be macerated, however, as directed under the preparation of sample, it is unnecessary 

 to employ a large amount. 



i Forsch. ii, Lebensm., 1896, 3, 141, and 1897, 4, 47. 



IT. S. Dept. of Agr., Bureau of Chem. Bui. 13, part 10. 



