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Tomato Paste
Cut the ripe, peeled tomatoes in halves and discard as many seeds as possible; set to cook in a white-lined saucepan over a slow fire; let cook until reduced to a paste, stirring occasionally. A "waterless cooker," a cooker with a separate bottom fitted with two or three asbestos pads, is good for this purpose. Press the tomatoes through a sieve fine enough to keep back any seeds remaining; add a teaspoonful of salt to each quart of material, mix, and use to fill half-pint, sterilized jars; adjust the rubber rings and covers; set the cans into a cooker, or boiler, and let boil one hour; tighten the covers and store as usual. It will take between two and three quarts of tomatoes to make enough paste to fill a half-pint jar. Without a waterless cooker, let cook on an asbestos mat. As the tomatoes are less liable to burn after straining, it is best to strain them as soon as they are softened throughout. This paste is used in mayonnaise dressing and for sauces, soups, etc.
A little goes a long way.
This is a home-canning procedure, and it is the canning part rather than the cooking part that fails modern standards. The points below explain what is wrong and what in the text is simply obsolete.
- No acidificationTomatoes hover close to the pH 4.6 line that separates boiling-water processing from pressure processing, and many modern varieties sit on the wrong side of it. Every current tested tomato recipe adds bottled lemon juice or citric acid in measured amounts; this one adds only salt, so there is nothing keeping the jars in the safe acid range.
- Density defeats the processPaste reduced from two or three quarts of tomatoes to a half pint is about as dense as a canned food gets. Heat moves through it by conduction alone, very slowly, so the hour of boiling described here gives no assurance that the cold spot at the centre of the jar ever reached a lethal temperature. Under-processed low-acid density is the classic setting for Clostridium botulinum.
- An unvalidated process timeThe instruction is simply "let boil one hour," with no jar-size table, no altitude adjustment and no note of whether the jars are packed hot or cold. Modern process times are the output of measured heat-penetration studies for one specific product in one specific jar; a general hour is not transferable.
- Use a current recipe insteadIf you want shelf-stable tomato paste, follow a tested recipe from a present-day extension or cannery source, or reduce the paste and freeze it in small portions. This text should be read, not followed.
- Asbestos padsThe "waterless cooker" with asbestos pads and the asbestos mat on the burner were standard heat diffusers in the early twentieth century. Asbestos is a known carcinogen and the pads should never be used or disturbed; a modern flame tamer or a heavy-bottomed pan does the same job.
- White-lined saucepanAlmost certainly enamel-lined ware, of the kind recommended for acidic fruit because reactive metals such as bare iron and copper discolour it. Stainless steel or enamelled cast iron is the equivalent today.
- Rubber rings and coversThe separate rubber gasket points to period hardware such as glass-lidded lightning jars or zinc caps rather than any modern closure, and the direction to "tighten the covers" after processing belongs to that hardware. Neither the rings nor the practice applies to modern two-piece lids, which must not be retightened after processing.
- YieldThe author's own figure is the useful one: two to three quarts of prepared tomatoes cook down to a single half-pint, a reduction of roughly sixteen to twenty-four to one by volume.
Tomato paste is the most concentrated form of the preserved tomato, and the technique long predates canning: in southern Italy conserva or estratto was made by spreading strained tomato pulp on wooden boards in the sun and working it down over days into a dark, salty block that was stored under oil. What this book describes is the same idea moved indoors onto a slow fire and finished in glass. Its appearance in an American household manual of the canning-boom years is a sign of how far tomatoes had travelled from suspicion to staple; a generation earlier they were still being defended in print as wholesome. The insistence on a slow fire, a diffuser and constant watchfulness reflects the real difficulty of the job on a coal or early gas range, where a paste this thick scorches the moment attention wanders. The closing line, "a little goes a long way," is the whole argument for making it at all: a half-pint jar carried the flavour of several pounds of summer tomatoes into winter soups and sauces.