Quote:
Originally Posted by coronabarb
This is why you shouldn't guess at processing times or think one size fits all. There are many factors that go into determining how to safely can foods. This is an explanation by an expert in Australia;
The timing given for any particular recipe is based on how long it takes for the entire contents of the jar to be heated to the safe temperature (240F - 250F) all the way through, and then it has to stay there for long enough to sterilise it. When they are testing recipes, they put little testing thermocouples in the jars that show the testers how fast the jars heat, whether it's even, and even how the heat moves through the food. Some ingredients are only recommended to be cut in particular ways because the size and shape of the pieces affects how fast and well they heat.
Some foods are dense - meaning they contain less water and air than other foods the same size, and they take longer to heat through and need longer processing. The ratio of solids to liquids can affect the rate of heating. Heat transfers more easily and quickly through liquid than through solids and dense mixtures, so a new canning process time would have to be determined through product testing if you were to increase the solid to liquid ratio.
Some foods have higher risk of spoilage because they naturally carry more fungi or bacteria on their skins. These also need longer processing times. And once they work out the minimum processing time needed to make a food safe for storage, then they also have to figure out the maximum time that you can process it without the food losing quality, either in texture and palatability, or in loss of vitamins and nutrition. The final times are based between those two to allow for variations in preparation and in the produce itself, and are designed to give home canners the best possible results in the safest but also the easiest way.
More details and explanation here;
http://nchfp.uga.edu/how/general/ens...ned_foods.html |
There is a lot of assumptions, guess work if you like, in these recommendations. There are temperature sensing indicators available or that could be slightly modified for home canning that are not being used. It is time this area was re-addressed. In the meantime, my 15 minutes at 15 PSI on a slurry which means homogeneous material seems as logical and practical as any of the plagiarized findings produced on the internet.