1919] AGRICULTURAL CHEMISTRY — AGROTI.< It N'Y. 713 



Tlie results show marked differences as well as similarities In the action of 

 the different strains, indicating that bacteria exert certain selective actions on 

 definite substances or groups of substances. The one common factor was the 

 Increase In the ammonia content, the significance of which Is discussed in 

 the following paper. 



Ammonia test for meat spoilage, K. G. Kai.k and Gk afcGtJIBS. (Jour. Biol. 

 Chem., 57 (1919), No. 4, pp. 5' f 7-550). — The marked Increase in ammonia eon- 

 tent of meat decomposing at room temperature, as noted in the above Investi- 

 gation, suggested the possibility of using tins factor as a chemical test for 

 Indicating spoilage of meat. This paper presents a discussion of the results 

 obtained in ammonia determinations by the aeration method and the permutite 

 method of Folin and Bell (E. S. R., 37, p. 311) on samples of meat (beef) un- 

 dergoing decomposition at room and at low temperatures. 



At ordinary temperatures bacterial growth was rapid, especially at the higher 

 temperatures, and the meat was soon unfit for use, in some cases after -\ 

 hours. At low temperatures, there was considerable growth of mold with little 

 bacterial growth, but after trimming off the mold the meat was still suitable 

 for use after standing for three or four weeks at a temperature varying be- 

 tween and 5° C, and for a much longer time with still lower temperatures. 



The ammonia content of the two forms of spoiled meat differed greatly. Tbe 

 fresh meat (beef within 24 hours of slaughter and chilled) contained between 

 0.03 and 0.1 nig. of ammonia nitrogen per gram of meat. Meat decomposed at 

 room temperature (15-25°) became unsuitable for food when the ammonia 

 nitrogen content reached from 0.3 to 0.4 mg. per gram of meat. At low tem- 

 peratures tbe ammonia content was much higher before the meat was unsuit- 

 able to eat, varying from 1 to 3 mg. 



In interpreting these results, especially in connection with the work of Hoag- 

 land and others (E. S. R., 36, p. 759) who considered the increase in amino 

 nitrogen to be the best measure of extent of autolysis in cold-stored meats, the 

 authors point out tbat at room temperature bacterial growth "is comparatively 

 rapid and the meat becomes unfit for food even with a low ammonia content. 

 At low temperatures, bacterial growth is slow, but autolysis proceeds so that the 

 cleavage products, such as ammonia and compounds rich in amino nitrogen, 

 increase greatly without the formation of those products whose odor, appear- 

 ance, and general flavor make the food unsuitable for use. If the meat Is kept 

 cold first, autolysis proceeding, and then is brought to room temperature, de- 

 composition would be much more rapid because of the simpler products formed 

 by autolysis, which would serve as nutriment for bacteria and greatly Incre - 

 their growth. This may be one reason, in addition to the physical effects of 

 the breakdown of cell walls by freezing, for the more rapid decomposition of 

 meat which has been In cold storage for some time." 



Note on the determination of blood sugar by the modified picric acid 

 method, S. It. BENEDICT (Jour. Biol. Chem., 57 (1919), No. J,, pp. 503, 50J t ).—T\w 

 author refers to the statement of Rohde and Sweeney, previously noted (B. S. 

 R., 40, p. 116), in regard to the failure of certain samples of the ptcrate-picrlc 

 acid solution to precipitate proteins or chromogenlc substances in the blood, and 

 states that 8 study of the question has shown that for proper precipitation Of the 

 blood tbe solution must have an acidity as high as X 20 or N '25, as determined 

 by titration of a portion of the solution with alkali, using phenolphthalein as 

 indicator. Titration of the final solution is said to be necessary only when a 

 portion fails to precipitate the blood properly. Such a solution may be cor- 

 rected by the addition of a quantity of glacial acetic acid sufficient t" bring the 

 acidity between N/20 and N/25. An excess of acid should be avoided. 



