So was born the tin can that now is scat tered in every direction, along the paths of travel and progress; but, strange enough, this growing infant had, in its younger days, another name, one which more became its fantile and clumsy form — °The Tin Canister.° In all the correspondence for the next 10 or 15 years, cans or canned goods never seem to be mentioned. They were always spoken of as hermetically sealed goods in canisters or tin cases. In the salesbook or °Waste," as it was then called, canisters were abbreviated thus, °Cans,° and probably by such abbreviations, tin packages for food came ultimately to be known as cans.
The stamp-can was invented in 1847 by Allen Taylor and was a decided improvement over any previously made. Two years later, 1849, Henry Evans, Jr., of New Jersey, brought forth the °pendulum)) press for making can tops, and so the improvement in the manufacture of cans has gone on till now we have the key-opened can, the invention of a Mr. Zimmerman. While the manufacture of cans has become a distinct industry and not now generally connected with the canning industry, nearly 10 per cent of those now in use are made by the canning es tablishments. These cans are made from sheets of tinned steel, 14x20 inches in size and weighing about one pound. The objection to tin cans as containing poisonous acid or in jurious substances has caused the methods of manufacture to be carefully scrutinized, so that now all cans are subjected to an acid prepara tion for removing dirt, grease, etc., and then coated with pure tin by the acid process or palm-oil process, the latter of which is consid ered the safer.
In the methods of cooking there have been many improvements, the slowness and low tem perature of 212° F. allowable in the Appert process being gradually raised by the use of chloride of calcium, till now a temperature of 250° F. is possible, although this process is more expensive, as the cans become discolored and have to be cleaned before they can be put on the market. The °closed-kettle° process of cooking goods by means of superheating water with steam was invented by A. K. Shnver of Baltimore, and about the same time, the in vention of the patent-process kettle, securing similar results by the use of dry steam, was brought out by John Fisher of the same city. One of the modern systems for sterilization is the Continuous Calcium Process System, pat ented by the Sprague Canning Machinery Com pany of Chicago. Another is the Continuous Process System in oil, used by the packers of canned meats. Another is the Polk Agitatin System, patented by Ralph Polk, of Greenwood, Ind. By this system the time of sterilization is materially shortened.
The canning industry, although established in the United States as early as 1825, did not become of much importance until the middle of the century, but from 1850 came to the front by leaps and bounds. In 1889 the products of
the industry were valued at $46,600,000; in 1899 at $99,335,000; in 1904 at $130,466,000; in 1909 at $162,000,000; and in 1914 at $235,000,000. This last tremendous increase appears to be partly fictitious, owing to the fact that more foods are now reported by the census under the heading of °canning.° For instance, condensed evaporated milk totaled $58,747,000 in 1914, or nearly one-sixth the entire production.
Many unaccountable losses were met with, when in certain years the canned goods would not all keep. Numerous theories were experi mented with, in vain efforts to learn the cause of these mysterious deteriorations.
In sonic cases it seemed certain that spoiling was caused by freezing. Some salmon had been stored in a warehouse, which, during the winter, had not been constantly heated. Many cans of this lot spoiled; so the freezing theory was accepted and held good, until some other cans from the same packing spoiled, which could not possibly have frozen. To explain this new phase of the situation, another theory had to be concocted.
In searching for the probable origin of these mysterious losses, the real cause was not suspected. The exclusion of air was thought to be one of the most important factors in keep ing the goods, and, until recently, this opinion has prevailed.
The researches in bacteriology in 1895-99 at the Massachusetts Institute of Technology brought out the fact that in some cases the spoilage of canned goods was due to imperfect sterilization through lack of sufficient heat to destroy all bacteria. This, however, accounted for only a small per cent of the spoilage cases. There are several other causes which have been brought out by the research work of Edward W. Dudcwall, M.S., in the Sprague Canners' Laboratory, an institution which was founded in August 1903 by Mr. Daniel G. Trench of Chicago. (The name of this laboratory has since been changed to the National Canners' Laboratory). It was discovered that a large per cent of what is known as "sour') corn and peas was due, not to insufficient sterilization, but to souring which had been accomplished by bacteria in the raw product prior to the steriliz ing process. It was also discovered that some of the spoilage was due to the evolution of carbonic acid gas from the seeds of certain fruits and vegetables. The germ life of the seeds was not destroyed by the heat, and car bonic acid was liberated when the seeds sprouted in the cans. Gradually all obsta. des are being overcome; new processes have been invented, the purity of the canned article has been proved by expert chemists and the manufacture has become general in every part of the United States where fruits or vegetables are grown or where the supply of fish and oys ters is nearby.