Converting processing times

[pmalin]

I am relatively new to canning, but have been reading a lot on it recently and doing a little of it too. I am sure there are others interested in this topic too. The typical thing is a recipe says to process for x amount of time in a water bath canner, but I have this nice pressure canner and I would like to know how much process time I need to use with it, instead.

First of all, I may need to ask if the quality of the product generally suffers from the increase in processing temperature, or is this typically an ok thing to do?

Now that we are past that, lets talk about some math. I am assuming (and if I am wrong please let me know) that the general math on this matter is a linear relation of Time X Temperature = Heating Units. Lets use units of minutes for time and units of F. for the temperature. The product will equal some amount of heating units, that I assume are un-named with these units being multiplied, Ill just call it heating units.

Ok, I have a recipe that calls for a water bath canning process time of 15 minutes. I have a pressure canner that operates at 15 psi, therefore is 250 deg during processing.

If I calculate the heating units for the original recipe 212 x 15 = 3180 heating units.

Now I know I need 3180 heating units to process it.

Now I transpose the formula and solve for the time it takes to process at 250 deg, and 3180 / 250 = 12.72 minutes.

Is this a legitimate method to convert or am I off on a wrong track here?

Thanks

 

[sparrowgrass]

Canning considers both time and temperature. You cannot can in a pressure cooker that is too small to hold 4 quart jars (upright) because the length of time to heat a small pressure cooker is too short.

I prefer to follow canning directions to the letter. The cost of doing it wrong is too high.

 

[GotGarlic]

Agree with sparrowgrass. It's better to find a tested recipe that is very close to what you want to do and use the time and pressure it does.