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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Canning-Corn
must be done with boiling water. Screw on the covers as tightly as possible, stand aside where the air will not strike them for one or two hours. Then put in a cool place to cool. When cool, again screw on the covers and put in a dark, dry place.
This fragment covers only the sealing and cooling stage of home-canned sweet corn, and the method it belongs to is one no current authority will endorse. The points below explain what fails.
- Corn is a low-acid foodSweet corn sits around pH 6.5, well above the 4.6 threshold below which Clostridium botulinum cannot grow. Boiling water reaches only 212F, which kills the vegetative cells but leaves the spores intact and viable.
- The sealed jar is the problemA tightly screwed, oxygen-free jar of moist, low-acid vegetable held at room temperature is close to an ideal incubator for those surviving spores. The toxin they produce is odourless and tasteless and does not necessarily spoil the appearance of the pack.
- "A dark, dry place" is not cold storageThe instruction to store in a cupboard rather than refrigerate reflects the era's assumption that a good seal was the whole of safety. Temperature, not darkness, is what governs spore germination.
- Retightening after coolingThe direction to screw the covers down again once cool belongs to the old glass-lid-and-rubber-ring era. With modern two-piece lids, retightening after processing can break a seal that has already formed and is specifically warned against.
- No processing time or temperature is givenEven taken as a period document, the text supplies no jar size, no processing duration and no vent or pressure figure. There is nothing here that could be scaled or corrected into a usable procedure.
- If you want to put up cornUse a current USDA or extension-service pressure canning procedure, or freeze it. Freezing sidesteps the botulism question entirely and suits corn better than any shelf-stable method.
Home canning of vegetables spread widely through American households in the second half of the nineteenth century, after the Mason jar and its screw-on zinc cap made a reusable, resealable glass container cheap and widely available. Cookbooks of the period taught canning as a straightforward matter of heat and an airtight seal: boil the food, fill the jar, exclude the air, and spoilage was thought to be prevented. "Sausage poisoning" was described in early nineteenth-century Germany, and the organism itself was identified in 1895 by van Ermengem in Belgium, following an outbreak traced to cured ham; the link between the organism, low-acid vegetables and inadequate home processing was not worked out and communicated to the American public until the 1910s and 1920s, when outbreaks tied to home-canned vegetables and to commercially canned olives prompted federal and state extension work on safe methods. Corn and beans were among the foods frequently implicated, and pressure canning came to be the recommended method for low-acid vegetables. A page like this one is a snapshot of the confident, pre-bacteriological approach that those outbreaks brought to an end.