“= pint Ris reese 
COMMERCIAL CANNING OF FOODS. 65 
can not be kept in the open without shrinkage and can not be marketed like white 
potatoes; therefore canning is used to extend the season throughout the year. ‘There 
are two varieties canned, the yellow or Jersey type, grown extensively in New Jersey, 
Delaware, Maryland, and Virginia, and the whiter or southern type, grown in the 
South. The former is preferred in most markets, owing, in part, to the better appear- 
~ ance, the color being a clean yellow. The southern type is sweeter but inclined to 
turn a rather dark, dead color and to become slightly watery. 
When the potatoes are received at the factory they are graded roughly for size, 
those more than 14 inches in diameter being placed in separate boxes so that they 
may be given a heavier cooking without overcooking the smaller ones. They are next 
washed, after which they are placed in crates, the layers not being more than 6 inches 
deep. The crates are then run into retorts and the potatoes given a steaming at 240° F. 
for from 9 to 12 minutes, depending upon their size and the length of time they have 
been out off the ground. The object is twofold, to heat the skins so that they will 
come off easily and to partially cook the potato before it enters the can. A quick, high 
heat applied for a short time will loosen the skin much better than a low temperature 
applied for a longer time. The peeling is done as soon as possible after the potatoes 
are taken out of the retorts, and, if the work has been well done, the peel is slipped 
off by squeezing between the fingers and not by cutting or scraping. The fresher the 
potatoes are from the ground the less steaming will be required, and also the less waste. 
Potatoes held for several weeks or allowed to dry in the air will show double the waste 
of those freshly dug. Peeling is also done by the lye process, such as is used for 
peaches, and is successful on the freshly dug product. In addition to the spraying 
they are vigorously brushed by revolving brushes, but there is always need for some 
hand trimming. The skin is also removed by means of the abrading machines used 
for white potatoes; these potatoes need hand trimming, as the machine does not 
rub in the creases and depressions. After preparation by lye or machine the potatoes 
are given a preliminary cooking to soften them before being packed in the can. 
The potatoes are rushed from the peelers to the filling tables so that they may be 
placed in the cans while still warm. Little attention is paid in filling to layering 
the potatoes in the cans, the object being to fill closely and then heap on a sufficient 
amount so that, when pressed down, the interstices will be filled. They are packed 
either wet or dry, the latter method being preferred. Some packers in putting up a 
“‘solid pack” add about an ounce of water to the can so that sufficient steam will be 
generated to prevent oxidation or darkening. The addition of any water is unneces- 
sary, and, as soon as packers learn how to handle this product, it is probable that 
the practice will cease. The filling should be strictly by weight, as that is the only 
method of securing a uniform fill. 
As soon as possible after filling, the potatoes should be given a thorough exhaust. 
The usual steaming for 3 minutes is insufficient, as the outside only is heated and the 
inside may be nearly cold. Cans examined in coming from the exhausts may show 
a temperature of 135° F. on the outside and top and only 70° or 80° in the center. 
As the heat penetrates the potato very slowly, a second heating in the retort or from 
12 to 18 minutes in the exhaust box is not unreasonable. If well heated the cans are 
not likely to be overfilled, as the expansion will be such as to cause a part to be thrown 
out before capping. If the right quantity has been weighed into the can and the lid 
lightly crimped on before exhausting, the contents will expand to fill all interstices. 
The packers know that the can must be well filled to preserve the clear bright yellow 
color, but if the exhausting is imperfect springers or flippers are almost certain to 
result. The bane of a slack-filled can is darkening of color and of the overfilled can 
is the springer, the correction of both being proper weight and exhaust. The sealing is 
done in the usual way, the general practice being to process for 3 hours at boiling heat 
for No.3 cans. Sterilization may also be secured by processing at 240° F. for 70 min- 
79258°—Bull. 196 —15——5 
