174 AGRICULTURAL BACTERIOLOGY 



cient amounts to accomplish the desired result without being 

 apparent to the taste. If their use were sanctioned by 

 law, materials unfit for food would be sold. 



Some of the condiments, such as cloves, cinnamon, and 

 mustard, contain essential oils that have a preservative ac- 

 tion that is more marked on molds than on bacteria. They 

 are used especially in pickles, catsups, mincemeat, and 

 fruit-cake. No regulations concerning their use are needed, 

 for the reason that the amount that can be added to a food 

 is limited because of their influence on flavors. 



In the smoking of meats, chemical compounds of the 

 creosote type are produced by the slow or imperfect com- 

 bustion of wood, and are deposited on the surface of the 

 meats. Certain woods, such as beechwood, yield a special 

 flavor that is much prized. Of later years the so-called 

 liquid smoke, which is a by-product of wood distillation, is 

 often used as a surface application. Its value as a pre- 

 servative depends on the disinfecting action of the creo- 

 sote. 



Organic acids. Organic acids are widely used in the 

 preservation of foods. The acids may be formed in the 

 foods by decomposition processes, or they may be added, 

 as in the case of the addition of vinegar to pickles. Sauer- 

 kraut is prepared by cutting cabbage and packing it tightly 

 in vessels with 2 per cent, of common salt. The pressure 

 and the action of the salt extract the juices from the plant 

 tissue. This liquid, which contains sugar, protein material, 

 and various salts, makes an excellent medium for the 

 growth of lactic-acid-forming bacteria. The amount of 

 acidity thus produced is sufficient to inhibit entirely all de- 

 velopment of putrefactive bacteria, As long as the acid 

 reaction is maintained, the kraut remains edible. The acid 

 may, however, be destroyed by the growth of molds and 

 veasts on the surface of the liquid, but if the sauerkraut is 



