Examine rubbers to see that they are in place. Sometimes, if the covers are screwed down too tight, the pressure of the steam from the inside causes the rubber to bulge out. Simply loosen the cover a thread or two, push the rubber back into place and then tighten. In case the rubber does not seem to fit well or seems to be a poor rubber, it should be replaced by a new one and the jar returned to the cooker for five minutes.
The jars should be sealed tight—covers screwed down, clamps put in place—immediately after they are removed from the cooker.
Invert to test the joint and cool. If the seal is not perfect, correct the fault, and return the jar to the cooker for five minutes if hot, ten minutes if jar is cold.
Do not invert vacuum-seal jars. These should be allowed to cool and then tested by removing the spring or clamp and lifting the jars by the cover only. Lift the jar only a half inch, holding it over the table so that, in case the lid does not hold, the jar and contents will not be damaged. Or, better still, tap round the edge of the cover with a ruler. An imperfect seal will cause a hollow sound.
Tomato Purée. Small, misshapen, unevenly ripened tomatoes may be converted into tomato purée. The tomatoes should be washed, run through a colander to remove skins and cores, concentrated by cooking to about half the original volume, and packed in the jars. Rubbers and tops should then be placed in position and the product sterilized for the same length of time as for canned tomatoes. Purée even may be kept in bottles sealed with sterilized corks and dipped several times in paraffin.
HOW OTHER VEGETABLES ARE CANNED
All other vegetables are canned exactly like tomatoes, with two exceptions. Tomatoes are scalded. All other vegetables are blanched. We scald tomatoes to loosen the skins and to start the flow of the coloring matter, which is later arrested or coagulated by the cold-dip.
Blanching is scalding, only for a longer time. Scalding is never for more than two minutes. Blanching covers from three to thirty minutes.
We blanch beans, peas, corn, cabbage, carrots, beets, turnips, and so on, for three to ten minutes. We blanch these vegetables to eliminate any objectionable acids or bitter flavors which may be present, and thus improve the flavor; to reduce the bulk so we can pack closer; to start the flow of the coloring matter; to improve the texture of the vegetables by making them more tender, and to improve the appearance by helping to make clear the liquid in the jar. Blanching is what makes for success in the cold-pack method of canning. Blanching is very important and must be carefully and accurately done.
Let me repeat about blanching: Have the kettle of blanching water boiling vigorously, completely immerse the product in the boiling water, cover the kettle immediately and begin to time the product. Do not stand with the cover in hand and wait for the water to come back to the boil, for, of course, it stopped boiling for a second when you lowered into it the cold product. If you cover the kettle the water will quickly reboil. Do not keep wondering if it is boiling and take off the cover to see. All these may seem foolish precautions, but it is necessary to follow directions accurately.