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| Image used for Illustration, Credit: www.vmahs.org |
Fruits and vegetables must first be sterilised before being sealed in airtight containers to preserve them. We examine some of the crucial steps in the process in this piece.
ACIDITY
There are two kinds of foods that will be canned. Foods that are high in acidity (pH 4.6) prevent bacterial development by being too acidic. Foods that are low in acid (pH > 4.6) must either have acid added to them (typically in the form of lemon juice or vinegar) or be sterilised at a higher temperature.
THE IMPORTANCE OF TEMPERATURE
Heating foods to the correct temperature is important because it kills microbes that might otherwise grow under some storage conditions. In the case of low-acid foods, you must use a pressure cooker to reach the required temperature. The temperature at which jars are stored can also affect the quality of canned produce.
BOTULINUM SPORES AND CANNING
Botulinum spores reside on most fresh foods. Though they're usually harmless, under the right conditions, they can germinate into bacteria that make deadly botulinum toxin. Acidity and temperature are key to preventing toxin production in canned goods.