When canning pumpkin, it is important to follow all instructions carefully and to ensure that all canning devices and equipment are used properly. Pumpkin is a dense vegetable, so it is harder to can safely than certain other foods. Pumpkin should only be canned when cut into cubes and when a lot of pressure is applied during the process. This helps to ensure that all potential botulism spores and other bacteria are killed efficiently.
Pumpkin should never be mashed or pureed prior to canning. Although pumpkin butter is a popular side dish and a staple for many recipes, it is not safe to make and preserve in residential kitchens. Those who want to use this ingredient should purchase commercial products. This is primarily due to pumpkin's dense nature, which makes heating mashed pumpkin thoroughly enough to kill all pathogens very difficult.
When canning pumpkin, it is important to only do so when the flesh has been peeled and cut into one inch (25.4 mm) cubes. Once the pumpkin has been peeled and cut, it should be boiled in water for two minutes. Clean, dry, jars should be available. The pumpkin should then be placed into the jars and covered with the cooking water. One inch (25.4 mm) should be left at the top of each jar.
The next step when canning pumpkin is placing each jar in a dual gauge pressure canner. The length of time each jar will need to be processed, and the pressure which should be used, will depend on one's altitude. The minimum length of time is 55 minutes, and the maximum is usually closer to 90 minutes. This ensures that each piece is thoroughly cooked and that all botulism spores and other pathogens are killed efficiently.
Once canned, cubed pumpkin can be stored for a very long time. The cubes can be mashed or pureed into pumpkin butter once they are removed from the jars. Some people don't find canning pumpkin to be worth the effort, since most types of winter squash have a naturally long shelf life. For instance, some pumpkins can last for months as long as they are not cut or punctured in any way. Pumpkin butter can also be made and frozen or kept in the coldest portion of the refrigerator for several months without going bad, although this can vary based on the refrigerator's temperature.
