One central problem that the canners worked to address was spoilage. Even though the canning process killed existing bacteria and created a vacuum seal to keep more bacteria from getting in, the method wasn’t always foolproof. If the temperature of the water bath was too low, or it boiled unevenly, or the pressure was insufficient, or the cans weren’t processed long enough, or the seals were weak—or if there were any other flaw in the process—spoilage could occur. Canners thus invested in bacteriology and public health oversight. With the acceptance of germ theory in the late 19th century, canners embraced this new awareness of the microbial life that could wreak such outsized havoc, seeing it as a key to solving their spoilage issues. Beginning in the 1890s, the industry sponsored scientific work to address bacterial contamination. Before long, canners felt they had gained control over this microscopic foe.
Most canned food spoilage is fairly obvious—either the can itself becomes deformed or its contents are visibly spoiled—and relatively harmless, perhaps leading to digestive upset or mild illness. But there was one rare kind of bacteria that was far from harmless: Clostridium botulinum.
This bacteria produces botulinum, the deadliest toxin known to humankind, which can’t be detected by sight, smell, or taste. Botulism doesn’t itself cause cans to be externally deformed, neither dented nor bulging, but those external signs often suggest an insufficient canning process, which can breed both botulism and other kinds of bacteria that have more visible effects. Botulism is also anaerobic, meaning it thrives in oxygen-free environments, precisely like that of canned food. Though it was rare, botulism terrified canners.
Their worst fears materialized in late 1919 and early 1920, when a series of deadly botulism cases struck unassuming consumers throughout the country, killing 18 people in Ohio, Michigan, and New York, with smaller outbreaks in other states. The deaths were traced back to canned black olives, a mainstay of hors d’oeuvre plates and a delicacy often reserved for special occasions. The olives had been packed in California and then shipped across the country to far-flung destinations, the result of a newly nationalized commercial food system.