456 MICROBIOLOGY OF SPECIAL INDtTSTSIES 



Desiccation, however, is only one of the agencies acting to preserve 

 the flesh. 



Jerked meat is sometimes prepared in localities with a hot dry climate. Lean 

 meat is cut into thin slices and exposed to the direct rays of the sun until dry. The 

 bactericidal action of the sunUght and the rapid extraction of moisture prevents 

 microBrganisms from producing undesirable changes during the curing process. 



Dried beef is lean meat which .usually has been treated with certain condiments or 

 smoked and salted and then dried. 



Dried fish such as cod, mackerel, and herring, is prepared by the use of condi- 

 ments, salt, and smoke in addition to the drying. 



Pemmican is prepared by drying lean meat, grinding it, and mixing it with sugar 

 and fat, dried fruits, spices, etc. It is highly nutritious, not unpalatable, and com- 

 pact, and will keep for a long period. It is frequently used as a concentrated form 

 of food by Arctic explorers, etc. 



Beef extract is prepared by cooking minced beef and water in a receptacle under 

 a slight steam pressure. The digestion is continued for several hours. The liquid is 

 filtered off and concentrated in a partial vacuum to the desired consistency. 



Gelatin is prepared by boiling bones and tendons, sometimes also horn and hide 

 scraps and concentrating the gelatin which dissolves from these. 



Somatose, sarco-peptone and related so-called predigested protein foods are mix- 

 tures of albumoses and peptones prepared by the artificial digestion and drying of 

 proteins, usually flesh. The product is marketed as a powder. 



Milk, either with or without its butter fat, is dried by being sprayed into a warm 

 compartment from which the air is partly exhausted. It dries immediately, in the 

 form of a very fine powder. This powder, if thoroughly dry, wiU keep well and is 

 finding an extensive use. The high sugar content of this powder is instrumental in 

 preventing the development of microorganisms. 



Eggs are dried in much the same manner as milk and the product is being used 

 extensively at the present time by bakers. 



Meats are frequently preserved by a combination of drying and the 

 action of certain antiseptics or preservatives. The salting of meat owes 

 its effectiveness in part to the abstraction of water. In most cases, 

 the surface of the meat and probably even the other portions are 

 protected in large measure by the diffusion of the fat and the satura- 

 tion of tissues and by the formation of water-proof fat films. The 

 autolytic enzymes are active in the fresh meat and soon become 

 inert upon the removal of water. The organisms responsible for 

 decay of preserved meats and flesh foods are usually bacteria. Some 

 of these break down the protein into simpler chemical compounds, of 

 which a few are poisonous. 



