Peas.—In packing peas, the peas are first removed from the pods by a machine, either a " viner" or a "podder." In construction the " viner " consists of a large hollow cylinder, enclosing a wire cylinder, within which a paddle wheel revolves rapidly. The vines are fed in at one end of the cylinder, and as they are struck by the paddles the pods are burst open and the peas dislodged, the bruised vines being delivered at the other end of the cylinder. The peas and fragments of leaves, pods and the like, fall on a broad endless rubber belt which travels up an inclined plane, where separa tion by gravity takes place, the peas rolling down into a trough while the lighter impurities are carried away by the belt.
In the "podder" the mechanism is still simpler. Instead of passing the whole vines into the machine, the pods are picked off by hand and these are fed into the machine through a hopper. The removal of the peas from the pods is effected in the same way as in the viner, and the peas and pods delivered by chutes.
From a bacteriological point of view, the latter process is the more desirable, as it leaves the peas clean and dry, while in the case of the " viner " they become wet and sticky with the juice of the bruised vines, and consequently more or less con taminated with dirt and dust.
After grading, i. e., separation by sieves into peas of different sizes, and further removal of fragments and poor peas, washing and blanching or scalding takes place. In this process much of the adherent dust and other contamination is removed, and the peas pass to the "filler" where they are delivered into cans, then to the "briner," where a boiling hot solution of sugar and salt is added. The cans are then sealed and are ready for the final cooking process or sterilization. This is done by steam under pressure, the length of time being determined by the age and quality of the peas. The temperature and time given varies with different manufacturers, ranging from 230° to 240° for thirty to forty minutes.
The fermentations which are likely to take place in case of insufficient sterilization are numer ous. There may be the formation of acids—lactic, acetic, and butyric particularly—with formation of gas; acid production (lactic) without gas forma tion; or putrefactive fermentation. The fermenta tions vary with the conditions and in many cases are due probably to mixed infection, thereby giving a large variety of products. These fermentations often take place rapidly, and are generally favored by a temperature of 35° to 40° C. (95° to 104° F.).
These rapid actions are generally accompanied by evolution of gases, sometimes the pressure of the gases generated being sufficient to burst the cans. In other cases, the action is very slow and but a small amount of gas is produced.
The sweating of green peas when allowed to stand in boxes has been studied to some extent by Underwood and the writer. Rapid fermentation takes place with the formation of acids and a slimy layer envelops the peas. Because of this action, peas should never be allowed to stand over night or for any length of time before being steri lized. The bacteria causing these fermentations have been studied by Prescott and Underwood.
Beans.—The canning of green beans or string beans is done in much the same way as the canning of peas. Baked beans, however, being somewhat denser and more resistant to the penetration of heat, require somewhat longer cooking in order thoroughly to sterilize. They are generally packed together with pork or with the addition of some sauce, as tomato.
Sweet corn is canned in immense amount in the United States. The corn is cut from the cobs by a machine, mixed with water and a little "brine," and heated in a "cooker," in which it reaches a temperature of about 80° C. (176° F.). Sugar is added in small amount and the heated corn is filled into cans and sealed immediately. The sterilization is done by steam under pressure of thirteen to fifteen pounds, and the time required for steriliza tion' varies with the consistency, percentage of access of bacteria to the saccharine juices. Unless means were taken to prevent it, fermentation would take place in a short time. An extended study of this fermentation has been made by W. L. Underwood and the writer. Several species of bacteria were discovered in cans of "sour" corn, some of these being able to resist five hours' boiling without being destroyed. Further investi gation showed the source of these germs to he the ears of corn. Bacteriological examination of healthy ears of fresh corn revealed the presence of germs on the kernels beneath the husks. These bacteria give characteristic reactions with nutrient media, and produce rapid fermentation of sugars, giving rise mainly to lactic acid, but also to forms of butyric and acetic acid. Sterilized sweet corn was converted in a few hours to a mass with strong acid reaction and sour taste. The most favorable temperature is 36° to C.