Wright. — Chemistry of Fles/i Foods. 5 ' 



The decomposition of flesh by bacterial activity involves putrefaction, 

 which is indicated by the production of ill -smelling compounds and the 

 formation of the simpler organic compounds, and if the changes reach the 

 limit the final products are water, ammonia, and carbon-dioxide. The 

 sulphur and phosphorus will be converted into sulphides and phosphates. 



Besides the chemical changes, there will be alteration in the structure 

 of the tissues. 



The deterioration of flesh foods is mainly a bacterial process, character- 

 ized in its initial stage by the conversion of the proteids insoluble in water 

 into water-soluble ones. The coaguable proteids are converted into pro- 

 teoses, peptones, meat-bases, and ammonia. This tendency is noticeable 

 almost at the beginning of the bacterial decomposition, the final end 

 of the process being the formation of the simpler compounds, such as 

 ammonia. 



To determine the conditions of bacterial decomposition portions of the 

 finely minced lamb and mutton were placed in flasks, mixed with water, 

 and an infusion of putrefying meat was added. The contents of the flasks 

 were examined at the end of two, four, seven, and fourteen days, and the 

 results are shown in Chemical Experiment No. 1 (Iamb and mutton), 

 Tables A, B, and C. A consideration of the figures shows a progressive 

 increase in the amounts of soluble matter in the flesh, in the case of the 

 lamb the total solids increasing from 5-18 per cent, to 9-12 per cent., the 

 total soluble nitrogen increasing from 0-708 per cent, to 2-461 per cent. ; 

 or if we turn to Table B, which shows the figures calculated to the moisture-, 

 ash-, and fat-free basis, we see that the organic extractives, which include 

 the soluble proteids, increase from 21-4 per cent, to 40-01 per cent. ; the 

 total soluble nitrogen, from 3-54 per cent, to 12-31 per cent. Still referring 

 to Table B, which shows the results in a more comparable form, we see 

 that the coaguable proteids increase from 11-14 per cent, to 17-55 per cent., 

 and then decrease to 14-22 per cent. Similar changes are noted in the 

 contents of proteoses and peptones. The amount of meat-bases com- 

 mences at 4-25 per cent., rises to 5 per cent., and then drops to 1-88 per 

 cent. 



It is, however, when we examine the ammonia figures that the most 

 striking alteration in the composition of the material is seen : commencing 

 with 0-158 per cent, ammonia, it increases to 0-51 per cent, on the second 

 day, and to 10-58 per cent. (Table B). 



At the very outset, whenever bacterial decomposition occurs, there is 

 a formation of volatile ammonia, and it is to the presence of this constituent 

 in relatively large amounts more than to any other that we must look for 

 evidence of decomposition, incipient or advanced. 



Thus we find in the case of the lamb that 75-37 per cent. (Table C) of the 

 total nitrogen has been rendered soluble, as against 21-68 per cent, in the 

 fresh sample ; and 53-35 per cent, of the total nitrogen is present in the 

 ammonia, as against 0-80 per cent, in the fresh sample. Similar results 

 are noted in the case of the mutton, the ammonia, commencing at 0-173 per 

 cent. (Table B) in the fresh sample, increases to 10 per cent, after fourteen 

 days, while 78-98 per cent. (Table C) of the total nitrogen is soluble at the 

 end of fourteen days, whereas 23-20 per cent, was soluble in the fresh 

 material, the percentage of nitrogen as ammonia rising from 0-91 per cent, 

 to 52-69 per cent, of the total nitrogen in fourteen days. 



We thus have before us a definite study of the changes we may expect 

 when bacterial decomposition ensues. 



