Important: Safety Warning
This page describes home-canning methods from before the causes of botulism were understood. Canning low-acid foods without a pressure canner, as described here, can allow the growth of Clostridium botulinum, whose toxin is among the deadliest known. Follow current USDA home-canning guidelines instead.
This information has been left in for historical purposes but should not be acted upon.
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Corn
Select perfectly fresh corn, remove the husks and silk, and carefully cut the corn from the cob. Corn for canning should never remain in the house over night. It is almost impossible to keep, doing your very best, and will not keep if not freshly picked. Pack the corn in the jars and press down closely, filling each jar to the very top. Put on the tops and screw them down. Arrange in a wash boiler as previously directed. Pour around the jars sufficient cold water, put the lid on the boiler and boil continuously three hours. Watch carefully, seeing that there is sufficient water to make a full volume of steam. When done, lift out the jars and screw down the covers as tightly as possible. Stand aside to cool, and when cold give them another screw and keep in a dark, cool place.
This is a boiling-water-bath method applied to one of the lowest-acid foods in the garden. It cannot be made safe by adjusting the timing, and the page itself carries a warning for good reason.
- Why corn specificallySweet 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 plain corn is an oxygen-free, moist, low-acid, room-temperature environment, which is close to the ideal culture condition for the organism.
- Three hours of boiling is not sterilisationWater in an open wash boiler reaches 212F. Botulinum spores can survive hours at that temperature; destroying them reliably requires roughly 240F to 250F, which only a pressure canner can reach. Long boiling cooks the corn without addressing the hazard at all.
- Packed solid to the topPressing the kernels down closely and filling to the brim makes a dense mass that heat penetrates very slowly, so the centre of the jar spends even less time near boiling than the outside does. It also leaves no headspace, so the closure is likely to fail or leak during processing.
- Tops screwed down before processingSealing the jars tight before heating traps expanding air and steam. Modern practice deliberately leaves bands finger-tight so air can vent; the repeated tightening described here is a period workaround for a type of closure now largely out of use.
- The toxin gives no warningBotulinum toxin is odourless and tasteless and does not necessarily swell the jar or spoil the appearance of the contents. There is no way to inspect a jar of home-canned corn and judge it safe.
- Corn for canning should never remain in the house over nightThis one line is sound and still repeated. Sugars in sweet corn convert to starch within hours of picking, and the surface bacterial load climbs quickly, which is why the author insists on same-day work.
- If you want canned cornUse a current USDA or extension-service pressure-canning procedure, or freeze the kernels instead. Do not adapt the method above.
Canning at home spread rapidly in the second half of the nineteenth century after the Mason screw-top jar made a reusable, resealable glass vessel cheap and widely available, and household manuals of the period are full of wash-boiler methods like this one, where the family laundry copper doubled as the processing kettle. The three-hour boil sits alongside the recipe's own admission that corn is 'almost impossible to keep', a difficulty whose cause -- a heat-resistant spore -- had not yet been connected to the failures. Botulism was described in the medical literature of the nineteenth century in connection with preserved sausage, but the specific danger of home-canned low-acid vegetables was not well understood by American cooks until the 1910s and 1920s, when bacteriological work and a run of outbreaks led extension services to press pressure canners on rural households.