SECTION 2
Water-Bath and Pressure Canning
4
WATER-BATH VERSUS PRESSURE CANNING
Learning to preserve food via canning is a great way to efficiently stock many different types of food for both daily use and emergency preparedness at a minimal cost. Another benefit is that you know exactly what goes into your jars; you don’t have to worry about hidden chemicals or loads of sodium.
Canning a variety of foods allows you to eat whatever you want at whatever time of year you like, and it will be just as delicious as when it was harvested. Remember that fresh fruits and vegetables from your own garden or from a farmers’ market are the best choices for canning. When done correctly, canning also preserves most of the nutrients in your foods, so in an emergency situation, you’ll still be well fed and you won’t need to worry about food fatigue.
Nearly anything you like can be made and canned, ranging from simple meals to delicious side dishes, condiments, and even complex desserts. Basically, what you preserve through canning is limited only by your imagination and a few basic rules.
Avoiding Botulism
For canning, foods are divided into two groups according to pH levels: strong-acid foods and strong-alkali (low-acid) foods. To prevent the growth of Clostridium botulinum, the microorganism that causes botulism, each group has its own method of canning.
Strong-acid foods can be canned using the water-bath, or boiling water, method of canning because their higher acid levels prevent the growth of the organism. Strong-alkali foods must be pressure canned because they require higher temperatures for longer periods of time to kill and inhibit the growth of C. botulinum.
Fruits, jams, jellies, fruit juices, pickles, tomatoes, relishes, condiments, salsas, and chutneys are all examples of strong-acid foods. See the chart below for the pH rating of some popular canning foods. High-acid foods are fairly easy to preserve and provide a whole new level of flavor to your cooking.
Vegetables, meats, and some sauces are examples of low-acid foods that need to be preserved using the pressure-canning method to destroy and prevent the growth of C. botulinum spores and other harmful organisms. This is a bit more complicated at first and requires special equipment, but pressure canning is a piece of cake once you get the hang of it.
Since strong-acid foods require the simpler method of canning (water bath), they tend to be more popular among beginners.
Water-Bath Canning
Water-bath canning is a relatively simple process that involves packing your food into jars and boiling them to increase the temperature inside the jars enough to kill residual bacteria and force air out of the jars so they seal. The environment inside the jars will then prohibit the growth of organisms that cause spoilage and disease.
All that you need besides jars, lids, and bands is a stockpot deep enough to submerge the jars in boiling water and racks in which to place the jars. Water-bath canners with jar racks that fit perfectly into the canner are readily available, relatively inexpensive, and preferred. This method is perfectly acceptable for use with high-acid foods that have a pH lower than 4.6, such as fruits and some vegetables. Tomatoes are typically canned as a high-acid food, but you should probably add a bit of vinegar, lemon juice, or citric acid to increase the acidity enough to create an environment prohibitive to C. botulinum.
With water-bath canning, racks are placed in stockpots or water-bath canners filled with water, and the pot is brought to a boil on a stove top. The filled canning jars are placed on these racks and processed (boiled) for specific times according to the food being canned. Then the jars are cooled, which is when the lids seal shut. Once the jars have cooled and the seals are tightly shut, bands are added to the jars and the food can be stored away.
Pressure Canning
As the name implies, this method of canning uses a pressurized canner to increase the heat inside the jars enough to kill C. botulinum in low-acid foods. This method has a dangerous element to it because you are dealing with a highly pressurized metal container full of hot water, food, and glass, so you need to exercise caution. That being said, it’s a perfectly safe process as long as you follow safety procedures, and it is an excellent way to preserve foods such as meats and vegetables.
Both types of pressure canning use a pot with a lid that typically has a rubber seal that swells and keeps the pressure inside the pot. The lid will have a steam vent or petcock in the top, which is a short, hollow pipe that goes from the inside to the outside and vents the pressure canner when it’s open or holds the steam in when it’s closed. This is what the gauge attaches to in order to regulate the pressure. Don’t ever remove this when the pot is pressurized. Pressure canners come in many sizes, and which one you choose will depend primarily on how many jars you want to process at one time. As in water-bath canning, metal racks are placed in the pressure canner, the canner is filled with water, and the jars are placed inside. The jars are processed under pressure (dictated by the foods you’re canning) for a certain period of time (also dictated by the foods you’re canning) and then removed to cool and seal.
There are two types of pressure canners: ones that use a weighted gauge and ones that use a dial gauge. A dial gauge actually has a pressure gauge on top that you set to the desired pressure and trust that it’s accurate. If you choose to use a gauge canner, you should calibrate your gauges at least once per year to ensure that they’re accurate. Even a few degrees can be the difference between safe-to-eat and botulism or other foodborne illnesses.
Another downside of dial gauges is the cost. Whereas you can pick up a weighted-gauge pressure canner for a few bucks at a thrift store, dial-gauge pressure canners are going to cost you significantly more. Also, dial-gauge canners simply have more moving parts that can break or cause inaccuracy.
Weighted-gauge pressure canners simply rely on a weighted piece of metal that’s simple, easy, accurate, and durable. It really is just a matter of personal preference, so whichever you’re more comfortable with, go for it. It should be noted that you can’t adjust the dial gauge to allow for altitude, so if you’re at a higher altitude you may be better off using a weighted-gauge canner.
Remember that regardless of which method you use, you’re dealing with extremely hot glass that, although tempered to be more tolerant to temperatures, will shatter with extreme changes from hot to cold or vice versa. Keep fans and drafts off your jars as you’re taking them from the pot and be gentle with them. Even tapping a hot jar on the edge of the counter can shatter it.
Whichever method you choose to learn first, you may want to borrow the equipment and purchase only a few jars to limit your investment until you know for certain that canning is for you. Start out with very simple foods and recipes, such as dill pickles, tomato sauce, or canned peaches, and gradually work your way toward more complex recipes and even trying your own variations. When you’re completely comfortable with both the science and the process of your first method of canning, then you can confidently start learning the other.