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Canned Rhubarb
Pare rhubarb and cut in one-inch pieces. Pack in a jar, put under cold water faucet, and let water run twenty minutes, then screw on cover. Rhubarb canned in this way has often been known to keep a year.
This is a cold-water, unheated pack — the jar is never processed, the contents are never brought to temperature, and the water is ordinary tap water. It cannot be recommended, and the points below explain what specifically goes wrong rather than how to fix it.
- No heat step at allNothing in this procedure kills anything. Sterilization of the jar, the lid, the fruit and the water is simply absent, and the twenty minutes under the faucet accomplishes only rinsing and displacement of air.
- No vacuum, so no sealA screw cover tightened over cold water produces no vacuum. Modern two-piece lids seal because steam displaces air and the cooling headspace contracts; a cold pack leaves a lid that is merely tight, and a merely tight lid admits organisms.
- Tap water is not a preservativeMunicipal water carries only a small residual of chlorine, on the order of a part per million or less at the tap — enough to keep a distribution system clean, nowhere near enough to preserve food for a year (and in the period this recipe was written, most supplies were not chlorinated at all). Well water contributes its own microbial load.
- Acidity is not a complete defenceRhubarb is genuinely acidic, around pH 3.1 to 3.4, which is why this trick worked often enough to be written down. But molds and yeasts grow happily at that pH, and mold growth raises the pH of the surrounding tissue over time, which is precisely how a low-acid pocket forms in a jar that was safe on day one.
- "Often been known to keep" is the tellThe original claim is anecdotal and hedged. Untracked failures — a jar that clouded, fermented or was quietly thrown out — do not appear in a cookbook. Current tested procedures for rhubarb specify a boiling-water bath with a stated time for the jar size; use one of those instead.
- The leavesOnly the stalks are food. Rhubarb leaves contain oxalic acid and related compounds at levels that cause real poisoning, and they should never go into a jar, a pot or a compost-to-table route. Trim and discard them entirely.
Cold-water canning of rhubarb appears in a number of late nineteenth-century American household writings, and its persistence has a plain physical basis: rhubarb is one of the most acidic things a temperate kitchen garden produces, acid enough to discourage many of the bacteria which worry canners, though molds and yeasts are another matter. That single fact let an otherwise indefensible method succeed often enough to earn a reputation. Rhubarb itself was known in nineteenth-century America as "pie plant," and it mattered out of proportion to its flavour because it arrived in April, weeks before any other fruit, at the end of a winter of dried apples and preserves. Fannie Farmer's book belongs to the moment when domestic science was beginning to test such inherited shortcuts against thermometers and bacteriology; the hedged phrasing here — "has often been known to keep" — reads like a compiler recording a common practice she was not prepared to guarantee.