Home canning can be a very rewarding activity. While your friends hit the supermarkets to pick up the latest in pesticide-ridden, greenhouse-grown fare, you can pop open a can of freshly grown produce. However, canning is not without its dangers. The constant threat of bacterial and fungal invasion into your canned goodies makes food poisoning a reality. For the safety of your family and friends, this article covers the proper way to sterilize jars for canning.
1. For foods which require less than ten minutes in the pressure cooker.
These foods are the most susceptible to bacterial growth because they are not boiled in the pressure cooker for an adequate amount of time to sterilize the food and jar. Sterilizing these jars, however, is a simple process. Using a boiling canner with a rack, place the jars upright in the rack and place the rack in the canner body. Cover the jars with water and boil them for at least ten minutes. Turn off the heat and keep the water warm until you are ready to use the jars. Simply pull the jars out of the water with a utensil (safety first!) and pack the jar with clean hands and tools. Can the jar as normal.
2. For foods which require ten or more minutes in the pressure cooker.
Certain foods do not necessarily require the boiling mentioned for the first category. These foods include tomatoes, fruits and other acidic foods. Because the jars will be boiled in the pressure cooker for more than ten minutes and because the acidic food environment is harmful to bacteria and fungus, odds are the jars will sterilize themselves during canning. However, there are some exceptions to this rule.
If canning meats or other foods very prone to bacterial contamination, it is still a good idea to use the boiling method described above. Also, if you live at high altitudes it is advisable to boil the jars an additional minute for each thousand feet in elevation above sea level. Recall from your physical science class in high school that water boils at cooler temperatures at higher altitudes, so longer boiling times are required to sustain a temperature that will kill bacterial growth. Remember, boiling does not sterilize anything – boiling is just a rough indicator that the temperature in the pot is high enough to kill bacteria.
3. For pickled and/or fermented foods.
These foods offer a unique perspective on sterilization. Pickled foods are either canned in an acid such as vinegar or in a hygroscopic liquid such as candied foods. Acidity provides a harsh environment for bacteria and fungus. Hygroscopic environments pull water from foods, bacteria and fungi, thereby inhibiting the growth of water-starved pathogens. Sugar and salt are the most commonly used ingredients in hygroscopic recipes – if your canning recipe calls for a large amount of either ingredient, odds are that they are used for preservation and flavoring so you should stick to the book.
Fermented foods are also interesting from a sterilization point of view because they use bacteria themselves to sterilize the environment. The best example is the action of bacteria in both yogurt and sauerkraut – they are fermented by bacteria with a byproduct of lactic acid. Once these bacteria are suspended due to refrigeration, the lactic acid they leave behind provides an acidic environment which prevents further bacterial growth.
In short, pickled and fermented foods require the least amount of canning jar sterilization. However, if you are feeling particularly germaphobic, you can use the boiling method described above. Keep in mind that the added heat in the jars may actually cause poor flavors and textures in pickled and fermented foods, so check the recipe for canning instructions to be sure.
Canning is a great family activity and can result in having healthy, fresh food year round. With proper sterilization, your canned foods can last a very long time. Just remember to store them in a cool, dry place and enjoy them often.