Pressure Canner

Until recently, water bath canners were used for storing almost all types of vegetables. They were even used for meat. Although water bath canners are helpful for storing acidic vegetables and fruits (such tomatoes, jellies, jams and apple butter), they are not appropriate for meat and vegetables which contain low concentration of acids. The reason is simple: water bath canners have a limited heating capacity. This means the temperature of the heated water rises to only as high as 212 F. However, the bacteria present in low acidic vegetables and meat, can easily tolerate such temperatures. Thus, a much higher temperature is needed to kill these bacteria – a thing that is not possible with water bath canners.

When manufacturers of water bath canners recognized such shortfall, they decided to modify their products so that these could support a higher temperature. The result was pressure canners. As the name suggests, pressure canners are capable of high pressure and, thus, high temperature. In fact, the temperature can be as high as 240 F. This is enough for killing most of the bacteria present in both acidic and low acidic foods. However, like water bath canners, they cannot be used for dairy foods.

A study conducted by the Ohio State University underscored the importance of pressure canners. The study found that a type of bacteria called clostridium botulinum is responsible for bringing about botulism (a severe type of food poisoning) in foods, especially in vegetables and meat that are low in acid content. The botulism is caused by the presence of spores of these bacteria in the food. These spores continue to thrive in low acid conditions, which usually contain a high content of water and a low content of oxygen. In order to prevent foods from rotting, these spores have to be killed. This can be done with the help of pressure canners.

The pressure canners are usually very light. Their walls are made of stainless steel or aluminum. There is a dial gauge which shows the pressure. Two racks that can be easily removed – called a steam vent and a safety vent – help to regulate the pressure. They are usually so big that several jars can fit inside them. Water then needs to be added to the pressure canner to build up pressure. The greater the amount of water, the higher is the pressure. In order to make sure that only the correct level of pressure is built up, the canner indicates the number of cups of water that are needed. After that, the temperature of the water is raised to the point the water starts boiling.

When the water is boiling, the user needs to make sure that there is only steam and not air in the canner. This can be done by opening the vents. The user should not remove the lid. In this way, water vapor will be formed in large quantities. This water vapor will drive out the remaining air from the canner. As a result, the jars will be present in only two media – steam and boiling water. Both steam and boiling water have similar temperatures. In case of pressure canners, the temperatures will be close to 240 F. This high temperature is a result of the high pressure formed in the canners. Hence, it is higher by almost 30 F than the temperature of the water bath canners, where the jars need to be submerged under water.

Pressure canners are usually very easy to use. However, the user needs to be very careful throughout the process – that is, from placing the canner on the burner, through building the correct pressure, to finally taking the jars out of the canner.Sometimes the pressure in the canners stars to fall. In this case, the user needs to increase the pressure by raising the temperature through the burner. People who are already at high temperature – that is, at a height of 1000 feet from the sea level – need to be extra careful.

This Pressure Canner Review is Written/Updated on May 5th, 2010 and filed under Kitchen Appliances. Both comments and pings are currently closed.

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