arsenic, zinc, or copper or any compounds thereof or any other poisonous or injurious substance. If the containers are made of tin plate they are outside soldered and the plate in no case contains less than one hundred and thirteen (113) milligrams of tin on a piece five (5) centimeters square or one and eight*-eenths (1.8) grains on a piece two (2) inches square. The inner coating of the containers is free from pin-holes, blisters, and cracks.
"If the tin plate is lacquered, the lacquer completely covers the tinned surface within the container and yields to the contents of the container no lead, antimony, arsenic, zinc, copper, or any compounds thereof."
Souring and Swelling of Canned Corn.—In all cases where sterilization
is not complete, or where spores remain undestroyed which afterward develop
and produce various kinds of ferments, the canned corn spoils. The contents
usually become sour and acquire a bad taste, and, in many cases, on puncturing
the container gas escapes. The pressure of this gas in the can is sometimes
great enough to produce a swelling, and hence the technical term "swelled"
applied to cans of this kind. Various forms of ferments are active in producing
these conditions. The usual alcoholic ferment does not usually occur
by reason of the fact that the yeasts which produce this form of fermentation
are readily destroyed in the sterilizing process. Ferments which produce
lactic, butyric, and other acids, and those which act upon the nitrogenous
matter and tend to form various decomposition products are the most
common.
In the case of canned corn and other canned vegetables the nitrogenous decomposed products are not usually very poisonous. On the other hand in the case of meat, and especially of fish and crustaceans, the degradation products from the nitrogen constituents of the food become poisonous and are known collectively under the name of ptomains.
If the sterilization has not been complete at the time of preparation, sweet corn as well as other foodstuffs in similar circumstances undergoes a kind of fermentation which renders it unfit for food. The fermentation is usually due to the greater vitality of spores and fungi, the real bacteria usually succumbing to the heat of preparation. Various gases beside carbon dioxid are produced, causing the corn to swell. All swelled goods should be rejected for food purposes.
Canned Peas and Beans.—These leguminous products lend themselves readily to canning purposes, and are preserved in great quantities in the United States in this way. Peas are always shelled before canning, and are harvested at a time to secure their greatest succulence. If the peas be too ripe they make a hard, unpalatable berry which detracts from the value of the canned product. The smaller variety of pea is preferred to the larger for canning, but, irrespective of size, they should be fresh, succulent, and not too mature. In the large canning factories the peas are harvested with machines such as are used for the cereals. The harvested material is passed
