Is there a difference between a pressure cooker and a pressure canner? A lot of people who approach canning for the first time ask themselves this question.
Well, the answer is that they are basically the same thing since they use pressure cooking as their cooking method. But, the cooker that you are going to use for canning has to have certain features.
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The main difference is the size
A pressure canner is larger in size than a pressure cooker. Canners have usually a capacity of 10 Quarts and more, because they have to be large enough to accommodate a certain number of jars on the bottom. So, you can use a larger pressure cooker for canning as well.
On the other hand, pressure canners can be used for pressure cooking, even though because of their large size and weight they are not very practical to handle for everyday cooking.
The material
Cookers are usually made of stainless steel, aluminum or combinations of both materials (aluminum is in the core of a stainless steel "sandwich"). Stainless steel is not a very good thermal conductor so aluminum (or even copper) is added to compensate it.
Most pressure canners are all aluminum.
The pressure settings
Pressure cookers usually have a working pressure of 15 psi (this is the standard). Usually, today's cookers come with an additional lower working pressure setting for the purposes of cooking more delicate ingredients and meals (like fish), but you are most likely going to use the 15 psi setting. A decrease to 12 or 10 psi will increase the cooking times.
Pressure canning require the use of different working pressures. The pressure you are going to use for your canning depends from the jar's size you are using, the acidity of the food you are canning and the altitude of your location. So, you need to increase it if you are canning low acidity foods or if your location is on higher altitudes. Buying a canner with three different pressure settings is ideal.
The gasket
Cookers usually have sealing rings made of rubber or silicone (gaskets) for the purpose of creating an airtight environment inside the cooker and preventing the air and steam from escaping.