What is too hot for home canning and storing canned foods? With the temperatures we have seen here in California's Central Valley recently, that is an excellent question! Seasonal produce is abundant and canning season is now in full production.
Any extended periods over 75 ° F or in direct sunlight can be detrimental to the seal and/or the food contents. Temperatures above 95 ° F can cause the growth of harmful pathogens causing the product to spoil and rendering the food potentially unsafe.
The excessive heat can cause the loss of nutritional value. Light exposure can contribute to the loss of nutrients and color changes, as well as hasten rancidity for products that contain fats or oils.
Light and/or high temps can heat the headspace air which may result in it to expend with the possibility of breaking the seal.
It is best not to process your canning in kitchens/rooms or outdoors when temperatures are over 75 °F. The jars “cool-down” time could become compromised with a negative impact. When jars cool down too slowly, thermophilic bacteria could grow causing the food to spoil, and rushing the cooling process is not an option.
Resource: El Dorado UCCE Master Food Preservers https://ucanr.edu/sites/mfp_of_cs/files/385761.pdf
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