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Spinach (Pick over the spinach wash)
Pick over the spinach, wash through many waters, then set to cook in about a cup of boiling water (to a peck). When tender, skim from the water and place in sterilized jars, packing it in solid; adjust the rubbers, strain the water in which the spinach was cooked through a napkin wrung out of boiling water, reheat to the boiling point, and use to fill the jars to overflow; put on the lids, let cook ten minutes after boiling begins, then tighten the lids.
This is a boiling-water process applied to a low-acid vegetable, and it is the textbook example of what home canning guidance spent the twentieth century correcting. The notes below explain the failure rather than repair it.
- Why ten minutes is not enoughSpinach is a low-acid food, with a pH well above 4.6. Boiling water reaches only 212F, which kills the vegetative bacteria but leaves Clostridium botulinum spores intact; in a sealed, oxygen-free jar those spores germinate and produce toxin. Only pressure processing reaches the temperatures that destroy them.
- "Packing it in solid" makes it worseDensely packed cooked greens form a mat that heat cannot penetrate. Even a much longer boiling-water period would leave the centre of the jar far below the temperature of the bath. Current guidance for greens calls for loose packing precisely because of this.
- The cooking liquid is not a preservativeStraining the spinach water through a scalded napkin and reboiling it sterilises the liquid at the moment of filling. It adds nothing to the keeping quality of the sealed jar, and no acid, salt or sugar is present to inhibit growth.
- Botulinum toxin gives no warningSpoiled low-acid vegetables can look, smell and taste normal. There is no reliable household test, which is why the process itself has to be right rather than the finished jar inspected.
- "Rubbers" and the closureThe recipe assumes jars sealed with a separate rubber ring, whether glass-lidded or zinc-capped, with the closure tightened after processing. That hardware is no longer in general use and its behaviour under heat is not comparable to modern two-piece lids, so the timings cannot simply be transferred.
- A peck, for referenceA peck is a dry measure of eight quarts, which for leaf spinach is only a few pounds of untrimmed greens, the leaves being very bulky for their weight. The single cup of water is a wilting liquid rather than a cooking liquid; the leaves release most of their own.
- If you want canned spinachUse a current tested procedure from a food-safety authority, or freeze the blanched greens instead. Freezing sidesteps the problem entirely.
Books like this one were common in the early twentieth century, when home canning was widely promoted as a patriotic and economic duty and the cold-pack or boiling-water method was taught for a great many things that came out of a garden. The distinction between high-acid foods, which the boiling-water bath does handle, and low-acid vegetables and meats, which it does not, was emerging among researchers in this period but was not consistently reflected in household manuals; agricultural extension services and, later, USDA bulletins were what pushed pressure canners into ordinary kitchens. The fussy details here -- the many waters, the napkin wrung out in boiling water, the reheated cooking liquor -- show a cook who took cleanliness entirely seriously, which is exactly why the recipe is instructive: scrupulous technique is no substitute for reaching the right temperature.