82 BULLETIN 908, U. S. DEPARTMENT OF AGRICULTURE. 
TABLE 35.—Compositwon of sardines (skinned and unskinned) stored in cans for 3 and 6 
months 
Period held. Water. Oil. Tin.1 
a 
Unskinned fish: Per cent. | Percent. |My. per kilo. 
SHMONGNS fe see aca Lis BE eateia ts See wae e noe eee eae eet noe 52.19 18. 88 194 
Dowecs ee nee On ee eee en Ae ARSE 52. 67 15. 64 2 66 
G:MONMS 3S5..22 ose wa ae ee ee oe ee ee Se ee rae 55. 00 16. 20 172 
Skinned fish 
Simonths fo = SS ae a eee ae ee ee eae Bee Ses 56. 00 14.93 225 
dB 0 SARs re sp itn ee Rs eee Ee Ate SS ees Sei aie 56. 81 14. 89 = - 85 
GATVONES HF ee ales Sens She Se ears eo ea epee ae 54.68 19.31 145 
DO wo. o cco Baie te toe ee ae Se Ae ae a ee eee 96. 13 17.81 | 3319 
| 
1 Determinations made by E. L. P. Treuthardt, Food Control Laboratory, Bureau of Chemistry. 
2 Least detinning in any of cans examined. 
3 Worst of lot, tarnished all over and one-half surface pitted. 
The tin removed from the can varied greatly among the individual 
cans, but in some cases corresponded to the amount of tarnishing or 
detinning undergone by the can. The tin content of the pack of 
skinned fish was, on an average, higher than that of the pack of 
unskinned fish. It was observed, incidentally, that detinning is 
reduced to a minimum when the cans are well filled with oil, and 
progresses more rapidly in cans where too little oil has been added 
or where the fish have absorbed the oil, thus removing the protective 
film between the fish and the can. The examination of these packs 
showed that the corrosion of the interior of the can was progressive 
and was more extensive in the packs composed of skinned fish. 
Apparently sulphur is equally distributed through the flesh and 
skin of the fish and is not primarily responsible for the corrosive action — 
of the contents of the can. The blackening of the areas detinned and 
the excrescences sometimes seen are due to the formation of iron 
sulphid. This probably is the extent to which sulphur enters into the 
reaction in the corrosion of the tinned plate. 
EFFECT OF AMMONIA AND AMINES. 
That the alkaline materials, ammonia and amines, are primarily 
the cause of part, at least, of the detinning which occurs in sardine 
cans was shown by the following experiments. 
Ammonia and amines, found in appreciable quantities in commer- 
cial and experimental packs of sardines, increase during storage 
(p. 70). That amines have a corrosive action on tin plate when con- 
fined in cans has been shown by experiments! in which monomethyl- 
amine of various strengths was sealed in cans and allowed to remain 
for different periods of time. Bigelow and Bacon(3) attributed the 
corrosion of the interior of tin containers used for canning shrimp to 
monomethylamine. A. Réssing(24) found the interior of cans in 
which sterilized lobsters and codfish had been preserved for several 
1 Unpublished results on file in the Bureau of Chemistry. 
