498 FOOD PRESERVATION 
and when air is allowed to come in contact with the brine or kraut, 
there is a vigorous growth of scum yeasts. Vats which showed an 
abnormal fermentation contained a different species of bacteria from 
the normal which got into the brine before the acid was high enough 
to prevent their growth. In a later paper (1917) Round states that 
the respiration of living tissuc is important in gas production. Bacillus 
brassice (Wehmer) and Bacillus cucumeris fermentate (Henneberg) 
represented the types which produced the greatest amounts of acid. 
smoking. Smoke has been used for a long time to preserve foods, 
especially meats. It probably acts by closing the pores of the meat and 
thus preventing the entrance of bacteria. The smoke contains different 
volatile products which are deleterious to the organisms causing putre- 
faction. The creosote compounds are also objectionable to certain 
insects which might pass their larval stage on it. 
Smoke also imparts a flavor to meats which is desired. This is 
especially true with meats which have passed through a pickle. Resin- 
inous woods are never used since these impart an undesirable flavor to 
the meat. Green hickory is advised for smoking under domestic con- 
ditions or corn cobs may serve as fuel. Under commercial conditions, 
pues of hickory logs are burned under the meat (hams). Toward the 
end of the smoking period, hickory sawdust is thrown on to give the hams 
a brown color (MacManus, 1917). 
McBryde (1911) has studied an economically important infection of 
hams known as ham souring. In advanced cases, the ham will possess 
a distinctly putrefactive odor while in the early stages the odor may 
be indefinite and a little ‘‘ off.” McBryde isolated an anaerobic bacillus 
(B. putrefacies) with which he satisfied the postulates of Koch. Since 
it is an anaerobic bacillus it develops in the deeper portions of the ham. 
The portions nearest the bone seem to be attacked first. 
Concentrated Solutions. The cell membrane should be regarded 
as a semi-permeable membrane and the passage of liquids through it 
is governed by the laws of osmosis and osmotic pressure. This is 
dependent upon the size of the molecule and type of substance in 
solution. The osmotic pressure is proportional to the number of 
molecules in solution. In salt and sugar solutions then, of equal con- 
centration by weight, the salt will exert a greater destructive action than 
the sugar which is present in a fewer number of molecules. 
Salt as a Preservative. Much more data are available in regard 
to the use of salt than carbohydrates. In this case it is used to prevent 
the growth of certain organisms and favor the growth of others. In 
early times salt served as currency and was too expensive to be used 
