1921.] Wright.—Chemical Technology of Meat Industry. 
161 
Pickled skins must be rigidly kept away from water, as in contact with 
it they swell excessively and rapidly become tender and rotten. 
The acidity of the pickled pelt is of considerable importance in main¬ 
taining its preservation from bacterial damage, it being necessary to have 
within the pelt conditions unfavourable to the growth of micro-organisms, 
either mould or bacteria. Salt alone, even if present up to 12 per cent, 
of the pickled pelt, is not sufficient to prevent the growth of organisms if 
the acidity is low. It has been found that 0-37 per cent, acid calculated as 
sulphuric does not prevent damage by micro-organisms. The course usually 
run when the acidity is low is that moulds, often Penicillium glaucum (a 
green mould) or Aspergillus niger (a black mould), which are capable of 
growing in a medium too acid for putrefactive bacteria, develop, and in 
the course of their living processes neutralize the acidity of the inadequately 
pickled pelt, until the reaction as regards acidity is sufficiently low to permit 
bacteria to grow ; and, since putrefactive bacteria are invariably present 
under commercial conditions, the pelts soon become damaged. It is thus 
important to see that the pickled pelts have a degree of acidity which is 
sufficient to prevent the development of moulds, as otherwise a cask which 
to-day may have but a few spots of mould upon the pelts may in the course 
of a month or so become damaged by putrefactive bacteria after the mould 
has reduced the acidity sufficiently for their development. An adequate 
acidity has been found to be 0-75 per cent, calculated as sulphuric. The 
lowest limit has not been determined, but an acidity below 0*5 per cent, 
should be regarded with anxiety. A red coloration produced upon pelts 
damaged by putrefactive bacteria was on one occasion found to be due 
to Bacillus prodigiosus . A typical analysis of a well cured and pickled 
pelt showed—Nitrogen, 2-75 per cent. ; hide substance, 16*10 per cent. ; 
sulphuric acid, 0*72 per cent. ; salt, 11*64 per cent. 
Hides. (28, 35, 47.) 
The hides, as soon as cool after removal from the animal, are washed 
with cold water from a hose, and then laid flat, hair side downwards; 
and the edges of the outer hides, after being freely sprinkled with salt, are 
turned in so as to slightly raise the outer edges of the pile of which it is 
to form the base, so that the salt brine which is produced by the partial 
solution of the salt may not run out, but must percolate through the 
hides. Each layer of hides as it is laid down is freely sprinkled with salt. 
A coarsely crystallized manufactured salt is used preferably, for crushed 
rock salt has been found to be unsatisfactory because of the fact that it 
usually contains an amount of iron and calcium sulphate, which marks the 
hide with what are generally termed “ salt stains.” The process is repeated 
till the height of the stack reaches the limit over which it is practicable to 
throw and spread the salt. In this stack the hides lie for two or more weeks, 
when it should be found that the salt has completely penetrated the hides, 
which are dried owing to the absorption of water by the salt and the drainage 
of the brine so formed. 
The purpose of salting the hides is to preserve them from bacterial 
decomposition, and in this connection the action of the salting is twofold— 
first, in abstracting a certain amount of water from the tissues and so partially 
drying them, and, secondly, the presence of the salt within the tissues in a 
concentrated solution is inhibitory to bacterial growth. 
The successful preservation of hides by salting is aided if the hides are 
stored in a cool dry store or cellar ; in addition, loss due to deterioration 
11—Science. 
