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Home-made Tomato Paste
When tomatoes are very plentiful, and the supply is greater than the immediate need, it is a good plan to make a paste, which will keep for some time in a I24 cool place. Wash and scald the tomatoes. Strain through a fine sieve, and boil until thick. Put in glass jars. This will be found very useful in flavoring soups and sauces.
This is a home-canning procedure rather than a dish to be eaten at once, and it omits every step that makes canning safe. The instructions below explain what is missing rather than how to correct it.
- No processing at allThe paste goes into jars hot and is left to sit in a "cool place." There is no boiling-water bath, no pressure processing, and no stated seal. The jars are not sterilised after filling, so anything introduced with the ladle, the jar or the air stays in the food.
- Botulism is the specific riskClostridium botulinum spores survive boiling, are common on soil-grown vegetables like tomatoes, and germinate in the sealed, oxygen-free, low-acid interior of a jar. Concentrated tomato paste is dense and slow to heat through, which is exactly the condition the organism needs. The toxin can be present with no smell, no bubbles and no off taste.
- Tomatoes are borderline acid, and modern ones more soTomatoes are borderline acid -- Tomatoes sit close to the pH threshold that separates safe water-bath canning from unsafe, and some varieties test at or slightly above pH 4.6. Current canning guidance requires measured added acid — bottled lemon juice or citric acid — in every jar. This recipe adds none.
- "Cool place" is not refrigerationAn unheated larder can sit well above refrigerator temperature for much of the year. Botulinum can grow at such temperatures, and "will keep for some time" is not a storage life anyone can act on.
- No quantities, no times, no temperatures"Boil until thick" and "put in glass jars" cannot be verified or repeated. Safe preserving depends on measured acidity, a known jar size, a known headspace and a timed process at a known temperature. None of those are here.
- If you want tomato pasteReducing scalded, sieved tomatoes to a paste is a sound way to use a glut; the problem is entirely in the keeping. Use a current tested canning recipe with specified acidification and processing times, or freeze the reduced paste in small portions.
Books of this kind exist because a household that grew or bought in bulk had no other way to deal with a glut, and The Cook Book of Left Overs treats a surplus of ripe tomatoes as the same problem as yesterday's cold potatoes. Concentrated tomato paste — conserva in southern Italy, where it was traditionally spread on boards and dried in the sun rather than boiled in a pot — has a long history outside the English-language kitchen. What the page shows most clearly is how little was understood about the mechanics of preserving at the time: the writer knows that boiling and a cool larder help, but the connection between acidity, sealed anaerobic jars and botulism was not yet part of ordinary domestic knowledge. Botulism was identified in the nineteenth century and linked to home-preserved food, but systematic, tested canning guidance for households only arrived with agricultural extension services later on.