XXI] MEAT AND MEAT PRODUCTS 281 



39 INSOLUBLE PROTEIN' ".-TENTATIVE. 



Dissolve 5 grams of powdered preparations, 8-10 grams of pasty extracts, or 20- 

 25 grams of fluid extracts, in cold water. Filter and wash with cold water. Trans- 

 fer the filter paper and contents to a Kjeldahl flask and determine nitrogen as di- 

 rected under 1, 1 8, 21 or 23. However, i f a large amount of insoluble matter is pres- 

 ent, transfer the weighed sample to a graduated flask, make up to a definite volume, 

 shake thoroughly, filter through a folded filter and determine nitrogen in an aliquot 

 of the filtrate. Deduct the percentage of nitrogen in the total filtrate from the 

 percentage of total nitrogen, 38, to obtain the percentage of nitrogen in the insol- 

 uble protein. Multiply this percentage of nitrogen by 6.25 to obtain the percentage, 

 of insoluble protein. 



40 COAGULABLE PROTEIN.-TENTATIVE. 



Prepare a solution of the sample as directed in 39. Employ as large an aliquot 

 of the filtrate as practicable or an aliquot of the filtrate from the insoluble protein, 39, 

 and neutralize to phenolphthalein by the addition of acetic acid or sodium hydroxid, 

 whichever may be necessary, add 1 cc. of N/1 acetic acid, boil for 2-3 minutes, 

 cool to room temperature, dilute to 500 cc. and pass through a folded filter. 



Determine nitrogen in 50 cc. of the filtrate as directed under I, 18, 21 or 23. 

 Ten times the percentage of nitrogen so obtained subtracted from the percentage 

 of soluble nitrogen (total nitrogen minus the percentage of nitrogen occurring as 

 insoluble protein) gives the percentage of nitrogen present as coagulable protein. 

 Multiply this figure by 6.25 to obtain the percentage of coagulable protein in the 

 sample. 



41 AMMONIA.-TENTATIVE. 



Mix 1 gram of meat extract with 2 cc. of N/1 hydrochloric acid, wash into a Folin 

 apparatus with about 5 cc. of water and proceed as directed under 15. 



42 PROTEOSES AND GELATIN".— TENTATIVE. 



Evaporate the filtrate from 40 to a small volume and saturate with zinc sulphate 

 (about 85 grams to 50 cc, avoiding such an excess as would later cause bumping). 

 Let stand several hours, filter and wash the precipitate with saturated zinc sul- 

 phate solution, place the filter and precipitate in a Kjeldahl flask and determine ni- 

 trogen as directed under I, 1 8, 21 or 23. Or, if the precipitate is voluminous, which 

 rarely happens, make up to a definite volume with saturated zinc sulphate solution, 

 filter and determine the nitrogen in an aliquot of the filtrate, as directed under I, 

 18, 21 or 23, and subtract the nitrogen thus obtained from the nitrogen in the 

 filtrate from the coagulable protein to obtain the nitrogen of the precipitated 

 protein (proteoses and gelatin). 



43 GELATIN.— TENTATIVE. 



Prepare a 50% solution of the sample, using hot water. Allow to cool and place 

 in an ice box for 2 hours. If gelatin is present, the solution will set. 



The ratio of total creatinin to total nitrogen in a normal meat extract (1 : 1.5) 

 assists in determining the presence of gelatin or gelatin derivatives. The ratio is 

 decreased when gelatin or gelatin derivatives are present in any considerable 

 amount. 



