Canning and Preserving for Beginners: The Essential Canning Recipes and Canning Supplies Guide. Rockridge Press
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process high-acid foods in a pressure canner, but water bath canning is quicker, so the choice is up to you.
Food Acidity and How It Affects Your Processing Method
Whether food should be processed in a water bath canner or a pressure canner depends on the acidity of the food you’re canning. Acidity can be natural, as with many fruits, or it can be added. The term pH is a measure of the acidity in a food; the lower the pH value, the more acid in the food. You can increase the acidity level in foods by adding lemon juice, citric acid, or vinegar.
High-acid foods contain enough acid to block the growth of Clostridium botulinum. High-acid foods have a pH of 4.6 or lower. These include fruits; pickles; jams, jellies and marmalades; fruit butters; and sauerkraut.
Low-acid foods don’t have enough acid to prevent the growth of the Clostridium botulinum bacteria, which is what causes botulism. Low-acid foods need to be heated to protect them. Low-acid foods have natural pH values higher than 4.6. These include meats, seafood, poultry, milk, and fresh vegetables, except for most varieties of tomatoes. When you create a mixture of low-acid and high-acid foods, that mixture also has a pH value above 4.6, unless the recipe also includes enough lemon juice, citric acid, or vinegar to make it a high-acid food. The chart below gives approximate pH levels for popular canning foods. Note that levels may vary with different varieties of the fruits and vegetables listed.
Note: Although tomatoes are generally considered a high-acid food, some of them have pH values slightly above 4.6. You should either add lemon juice or citric acid to these varieties, or use a pressure canner to process them.
Botulinum bacteria are almost impossible to eliminate simply by bringing them to a boiling temperature (212 degrees F). This is why low-acid foods need to be processed at temperatures between 240 and 280 degrees F.
In a pressure canner, this means processing the food at 10 to 15 psi. The abbreviation psi means “pounds per square inch of pressure,” which you measure by using the pressure gauge located on or near the lid of the canner. At temperatures of 240 to 280 degrees F, the bacteria in low-acid canned food can be destroyed in 20 to 100 minutes. The exact time it will take depends on the kind of food you’re canning, the way it is packed, and the size of the jars you’re using. The time needed to safely process low-acid foods in a water bath canner would range between 7 and 11 hours, but the time needed to process high-acid foods using a water bath canner only runs between 5 and 85 minutes.
Processing time using either pressure canning or the water bath method depends on:
• the type of food
• the altitude of your geographic location
• the recipe’s acidity
• the size of the jars
Each of the recipes in this book includes processing times.
Fresh produce from your garden or a farmers’ market is the best choice for canning.
Selecting Produce for Canning
Canning does not make mediocre foods taste more palatable, nor will it rescue food that’s about to spoil. It’s important to be choosy when selecting the foods you’ll be canning; that way, your canned foods will be delicious and safe to eat.
Choose the Best Quality You Can Find
Fresh is best and fresh in season is even better. Canning began as a way to preserve the best flavors of a given season, in addition to putting food up for the non-growing season.
Pick fruits and vegetables that are at their very peak of flavor. This means buying in season as much as possible and locally, if available in your area. Foods picked before they’re ripe and shipped thousands of miles will lack the flavor of locally sourced foods. This means you should be looking for strawberries in June and in the fall, fresh peas in the spring, and so on. Many types of produce have long growing seasons, especially if you live in a more temperate climate, so it’s fairly easy to buy them fresh and flavorful for much of the year. Cucumbers, beans, and tomatoes are good examples.
If you’re not able to grow your own produce, try to purchase foods for canning at a farmers’ market or from a local farmer. Organic produce is always a good choice for canning, and farmers may be willing to give you a price break on the larger quantities for a day of canning.
Inspect Your Produce Carefully Before Processing
If you’re buying your produce by the case, bushel, or bucket, be sure to carefully inspect each piece as you wash it. Discard anything that appears to have mold on it (either green or a thin, white coating near the stem). Also be sure to toss anything that has holes, cuts, or other openings that could be portals for bugs, insect eggs, or bacteria.
Tips to Avoid Spoilage
The last thing you want after carefully growing, choosing, and canning your wonderful foods is to lose some of them to spoilage. More important, you don’t want anyone to become ill from eating spoiled food.
Canning is a safe way of preparing and preserving fresh foods as long as you follow the recipes and instructions carefully. The following additional tips can help you can foods successfully and minimize the chances of spoilage:
Always follow the guidelines in the following sections for testing the seals on your canned goods before you store them away. If you are ever in doubt about the seal or if a jar has not sealed properly, either refrigerate it and use immediately, throw it away, or reprocess it. Reprocessing is recommended only for foods that do not contain meat, eggs, or seafood. (To reprocess, prepare another sterilized jar, bring the food to a boil in a saucepan, and pour it into the new jar. Cover and process for the required time, and allow it to sit undisturbed for another 12 to 24 hours.)
Have enough clean towels on hand so you can wipe each jar with a fresh section of towel. Once a section of towel has become soiled with liquid or food, use a new section or a new towel.
If you’re canning more than one type of food, always wash your utensils, cutting boards, knives, and other tools before moving from one food to another.
Can only what your family can eat or give away within a year. Always mark the jars accordingly, and eat the oldest foods first. A good practice is to write the canning date in marker on the lid and write the expiration date on the label. When adding new jars to a shelf, move the older jars to the front and store the newer jars behind them.
Always store your canned goods in a cool, dark place where they will be safe from jostling. Never store canned foods in movable storage such as totes or under-bed storage boxes, as frequent moving can result in chipped or cracked jars and cause contamination.
SECTION 1
Water Bath Canning
Chapter 1: Water Bath Canning: Supplies, Instructions, and Safety
Chapter 3: Jams, Jellies, and Preserves