Different foods are preserved more effectively through different canning methods. You don’t want to can some jam and find out it's rotten a few days later due to bad canning. (Related: The easiest foods to can.)
Before canning, check the pH factor of your food. The pH factor refers to the levels of hydrogen ion activity in a solution. The measurements range from 0 to 14, with 0 being the most acidic and 14 being the least acidic (basic or alkaline).
Acidic foods – those that have a pH level of 4.6 and below – can be preserved through boiling water bath canning. Foods with pH levels greater than 4.6 usually must be preserved using a pressure canner.
You need a pressure canner for low-acid foods because they might contain bacteria called Clostridium botulinum. They produce a potent toxin called neurotoxin botulinum, which causes foodborne botulism. This can lead to paralysis and even death.
With a pressure canner, you can increase the heat to 250 F, the prescribed temperature which kills C. botulinum spores. This way, low-acid foods are safely preserved and sterilized.
Note: Acidity and pH levels are not the same. Some foods can be acidic but still have pH levels greater than 4.6. If you want to can them, add lemon juice or citric acid to reduce the pH level. Some examples include tomatoes and figs.
Foods with low pH levels naturally contain acids, which prevent the growth and spread of harmful bacteria. When heated, these compounds become more effective at killing bacteria. Therefore, it is safe to use the boiling water bath canner.
Some acid foods include apples, blackberries, raspberries, strawberries, pineapples, plums, oranges, peaches, pears, and gooseberries.
On the other hand, low-acid foods need a pressure canner. To ensure safety, do your homework and search for tested recipes. By practicing, you'll get better and be able to start making your own.
Some low-acid foods good for canning are red meats, seafood, poultry, and fresh vegetables.
You now have a basic understanding of food canning. However, if you lack the time to can your produce or you simply don’t have the equipment for it, there are other ways for you to preserve food. Some of these include: