Important: Safety Warning
This page describes home-canning methods from before the causes of botulism were understood. Canning low-acid foods without a pressure canner, as described here, can allow the growth of Clostridium botulinum, whose toxin is among the deadliest known. Follow current USDA home-canning guidelines instead.
This information has been left in for historical purposes but should not be acted upon.
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Canned Tomatoes
Wash the tomatoes and plunge them in boiling water for about five minutes. Pare and cut them into small pieces; put them in the preserving kettle over the fire and heat slowly, stirring frequently to prevent their sticking, and removing the scum that rises. Boil for thirty minutes, counting from the time the whole mass begins to boil. Put in sterilized jars and seal. If canning by the cold-pack method, blanch, cold dip, and peel tomatoes; pack the best into the jars. Put the imperfect and broken pieces in the preserving kettle. Boil ten minutes. Strain, and pour over the tomatoes packed in the jars. Add one teaspoon salt to each jar. Process in sterilizer according to time-table.
This is a genuine recipe, but it is a preserving method that current food-safety practice has retired. The problems are specific to tomatoes and to the equipment assumed here.
- Tomatoes are not reliably acidicThe old assumption was that tomatoes were acid enough to protect themselves in a sealed jar. Some varieties, and overripe fruit of any variety, sit near or above pH 4.6, the line below which Clostridium botulinum cannot grow. Nothing in this recipe measures or adjusts acidity, so the jar may or may not be in the safe range, and there is no way to tell by looking.
- Boiling does not destroy the sporesThirty minutes at a rolling boil kills the bacteria but not their heat-resistant spores. Sealed into an oxygen-free jar of low-acid pulp at room temperature, those spores can germinate and produce toxin, with no reliable smell, bulge or off flavour to warn the cook.
- "Put in sterilized jars and seal" is open-kettle canningHot food ladled into hot jars and sealed with no further heat processing was standard practice for decades and is now specifically advised against. The seal it produces is unreliable and the contents receive no measured heat treatment at all.
- The salt is not a preservative hereOne teaspoon per jar is a seasoning quantity. At that concentration it has no antimicrobial effect on the packed tomatoes and should not be read as doing preserving work.
- "Process in sterilizer according to time-table"The cold-pack instruction defers entirely to a table printed elsewhere in the book. No time or temperature appears on this page, so even a reader willing to follow it has no processing figure to follow.
- What to do insteadHome-canned tomatoes are still entirely practical, but only with a current USDA or extension-service recipe, which will specify added bottled lemon juice or citric acid per jar and a tested processing time. Use one of those rather than adapting this.
The two methods given here mark a transition: the older open-kettle style, in which the food was cooked down and sealed hot, and the newer "cold pack" promoted by state extension services and the canning clubs of the 1910s, which packed raw fruit and processed the filled jar. The thrifty detail of setting aside "imperfect and broken pieces" to boil down for the covering liquid is characteristic of the period's kitchen economy. Tomato acidity, long taken for granted, would later be found variable enough to require measured acidification.