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Canned Corn
Cut fresh young corn from the cob. Pack sterilized jars to overflowing with corn. Seal, set on trivet in boiler, surround with cold water, and boil five or six hours, having boiler covered all of the time. Keep in dark, cool place.
This is a boiling-water-bath method for a low-acid vegetable, and it is the single canning procedure that modern food-safety authorities rule out entirely. The points below explain what fails here rather than how to adapt it.
- Corn is low-acid, and that is the whole problemSweet corn sits around pH 6.0 to 6.8, well above the 4.6 threshold below which Clostridium botulinum cannot grow. A sealed jar of corn is an oxygen-free, low-acid, room-temperature environment, which is precisely the condition botulinum spores need to germinate and produce toxin.
- Boiling water cannot reach the required temperatureWater at sea level boils at 212F. Botulinum spores are not reliably destroyed until the food itself is held at 240F or above, which only happens under pressure. Five or six hours at 212F does not substitute for temperature; the spores survive a long boil that merely cooks the corn to mush.
- Whole-kernel corn is dense packCorn packed "to overflowing" forms a solid mass with almost no convection. Heat moves through it by conduction alone, so the centre of the jar lags far behind the water temperature for hours, which is why corn is among the hardest vegetables to process even in a pressure canner.
- Sealing before processingThe instruction to seal, then boil, leaves expanding air and steam little way to vent. With modern two-piece lids this can produce buckled lids and false seals; jars sealed tight before a long boil were also liable to break. Either way there is no reliable way to tell a good seal from a failed one afterwards.
- No acid, no salt, no measured headspaceThere is nothing in the jar to lower pH, no brine ratio, no headspace figure and no cooling or seal-testing step. Every variable that a tested canning procedure controls is left open here.
- Botulinum toxin gives no warningSpoiled canned corn can look, smell and taste normal. "Keep in dark, cool place" was sound storage advice for the period but does nothing to make an under-processed jar safe, and cool cellar temperatures are still well within the growth range.
- If you want canned cornUse a current pressure-canning procedure from a tested source, or freeze the cut kernels instead. Do not adapt the method above.
Lowney's Cook Book appeared in 1907, at the tail end of the long period when home canning was done in a wash boiler on the kitchen range and success was judged by whether a jar spoiled. Botulism from home-canned vegetables was not understood as a distinct hazard until the 1910s and 1920s, when outbreaks traced to home-processed low-acid foods prompted research at the University of California and elsewhere; the pressure canner, though patented in the nineteenth century, only became common domestic equipment in the 1920s and 1930s as extension services pushed it. Long boiling times like the five or six hours here were the era's attempt to compensate for a temperature they had no way to raise, and some canning literature of the period recommended processing on several consecutive days, a practice known as intermittent sterilisation. The recipe is a useful record of what careful cooks believed was sufficient, and of how much the science changed within a generation of its printing.