534 MICROBIOLOGY OF FOODS 



After the pieces have been selected and dressed they are parboiled before being 

 placed in the containers, the time ranging from eight to twenty minutes, according to 

 the size of the pieces. The object of parboiling is to secure the shrinkage which 

 always takes place on heating. Meats put into tins in the fresh state and processed 

 shrink to about two-thirds of their original volume. When the meat is put directly 

 into boiling water, there is less loss of protein than when placed in cold water and 

 heated gradually. During parboiling, the meat loses about i per cent, of the pro- 

 tein content, about one-third of the total meat bases, and 50 per cent, of the mineral 

 matter. 



This shrinkage by parboiling tends to make a more concentrated article, thus 

 favoring transportation, and, pound for pound, the nutritive value is not lowered. 

 Practically, the nutritive value of a pound of properly canned beef is about 

 one-third greater than that of i pound of fresh beef of the same kind. After par- 

 boiling, the meat is placed in tins and a quantity of meat jelly is added to prevent 

 the meat from adhering to the tin in spots, and also to give it a better appearance. 



Some meats are partially cured before canning, as corned beef. Sausages, and 

 minced, devilled, and potted meats are cooked and run through meat cutters or 

 grinders. These products are generally made from meat trimmings and pieces too 

 small to use in the regular way. Some of these contain mixtures of meats, some 

 cereal, and others spices. The packing of chicken, turkey, and game follows the 

 general routine of meat packing. 



Fish. The process of fish canning does not differ materially from that of other 

 meats. On account of its proneness to rapid decomposition, especial care must be 

 observed that the fish are in a perfectly fresh state before canning, and that the 

 processing be most thorough. The salmon is preeminently the sea-food in cans in 

 this country, the value of the pack being nearly equal to all other sea-foods com- 

 bined. Further, salmon is the principal fish for the preservation of which depend- 

 ence is placed on sterilization alone, most fish being preserved by other methods. 



Vegetables and Fruits. Corn. Sweet corn only is used. The young tender ears 

 of sweet corn are picked from the stalk, preferably in the early morning, keeping the 

 husks on, and are taken in this condition to the factory. They are husked and the 

 silks removed and passed through machines with sets of knives which cut the grains 

 evenly from the cob, care being observed not to cut the corn so closely as to cut off 

 particles of the cob with the corn. In some cases the cobs are next passed through 

 scrapers which remove the small tips adherent to the cob. After the corn is cut it is 

 run through a cleaner which removes bits of cob, husk, and silk. It is then passed 

 to a mixer and the proper amount of water, bearing sugar and salt in solution is 

 thoroughly stirred through the mass. It is then run into the filler and cooker. Most 

 of the operations are done by machinery, and the different processes follow each other 

 in such rapid succession that from the time the ear goes into the husking machine 

 until the corn is* in the can, sealed, and ready for the retort may not be more than 

 fifteen minutes. 



Peas. In the pea-canning industry the vines are cut with a mower or a special 

 pea harvester, loaded onto racks and hauled to the vining machines. The viner is a 

 machine consisting of an outer and an inner cylinder revolving in opposite directions, 



