Wright, Bevis, and Nelson.— Chemistry of Flesh Foods. 481 



while 94-3 per cent, of the meat-bases and 99 per cent, of the chlorides 

 are thus soluble. 



From a consideration, therefore, of the results it is seen that the meat- 

 bases, to which is due the principal physiological value of a meat-extract, 

 are nearly completely soluble in 80 per cent, alcohol ; consequently the 

 results obtained by the commercial method of valuation are in agreement 

 with the physiological. 



The nitrogenous constituents insoluble in 80 per cent, alcohol are 

 principally compounds similar to gelatine ; and, while gelatine has a physio- 

 logical value as a sparer of protein in metabolism, it has but little value 

 as a food. 



Non-putrescence of Solid Meat-extracts. 



It has been a matter of common knowledge that solid meat-extracts 

 do not undergo bacterial decomposition. While this fact has been noted 

 in connection with the report of the Commission appointed to investigate 

 the methods of manufacture of meat-extracts (8), the question has arisen 

 as to whether in the absence of special precautions solid meat-extract 

 remains free from bacterial growth and decomposition. Commercially it 

 is known that even after a period of several years solid meat-extract has 

 been found to be undeteriorated. In order, however, to ascertain whether 

 there is any evidence of bacterial or other decomposition we have made a 

 number of determinations covering extracts which have been held in jars 

 with loosely fitted tops after exposure to the atmosphere ; these extracts 

 have in some cases been held for as long as six months. 



As is well known, ammonia is one of the decomposition products of 

 nitrogenous foods, and the determination of the loosely bound nitrogen 

 as ammonia which occurs in the nitrogenous constituents of meat-products 

 has proved to be one of the most reliable methods for indicating the 

 decomposition or otherwise of such substances ; it has been shown that 

 a marked rise in the amount of ammoniacal nitrogen occurs in meat pro- 

 ducts before the senses can detect any decomposition (11. 12. 13 ; 14. 15). 



The methods used in the determination of the ammoniacal nitrogen 

 were (a) the magnesium-oxide distillation method (9), and (b) Folin's 

 aeration method (10, 16). 



(a.) The magnesium-oxide method used was as follows : 1 gramme of 

 the extract (or an aliquot portion of a solution of the extract equal to 

 1 gramme of extract) was placed in a distillation -flask with 300 c.c. of 

 water and 5 grammes of magnesium oxide free from carbon dioxide ; after 

 connecting the flask with a condenser, 100 c.c. of the liquid was distilled into 

 N/50 acid, and titrated as usual, using congo-red as an indicator. 



(b.) The Folin aeration method used was as follows : An aliquot portion 

 of a solution of the extract equal to 1 gramme of extract was placed 

 in a large tube; 0-5 c.c. saturated solution of potassium carbonate and 

 1 c.c. saturated solution of potassium oxalate with 2 c.c. kerosene (to mini- 

 mize frothing) were added. The mixture was aerated from a water-blower 

 with water-injector pump, the air being passed through 30 per cent, sulphuric 

 acid in order to remove any traces of ammonia before passing through 

 the aeration -tube. The period of aeration was four hours, at the rate of 

 80 litres of air per hour ; the ammonia from the extract was collected 

 in N/50 acid through which the air from the aeration -tube was passed ; 

 congo-red was used as an indicator. 



16— Trans. 



