your jars with care
You have picked your food and washed it carefully. Now, you are in the home stretch, and the way you fill the canning jars is super important:
Don’t overpack foods. Trying to cram too much food into a jar may result in under-processing because the heat can’t evenly penetrate the food.
Make sure your jars have the proper headspace. Headspace is the air space between the inside of the lid and the top of the food or liquid in your jar or container (see Figure 3-2). Proper headspace is important to the safety of your preserved food because of the expansion that occurs as your jars are processed or your food freezes.
Make sure you release the air bubbles from the jar before sealing the lid. No matter how carefully you pack and fill your jars, you’ll always have some hidden bubbles.
FIGURE 3-2: Headspace.
Taking a closer look at the all-important headspace
When you’re canning food, too little headspace in your canning jars restricts your food from expanding as it boils. Inadequate space for the expanding food may force some of it out of the jar and under the lid, leaving particles of food between the seal and the jar rim. If this occurs, your jar won’t produce a vacuum seal.
Leaving too much headspace may cause discoloration in the top portion of your food. Excess headspace can keep your jar from producing a vacuum seal if the processing time isn’t long enough to exhaust the excess air in the jar.
Always use the headspace stated in your recipe. If your recipe doesn’t give you a headspace allowance, use these guidelines:
For juice, jam, jelly, pickles, relish, chutney, sauces, and condiments, leave a headspace of ¼ inch.
For high-acid foods (fruits and tomatoes), leave a headspace of ½ inch.
For low-acid foods (vegetables, meats, fish, and poultry), leave a headspace of 1 inch.
Releasing air bubbles from your jars
The most important thing to do when you’re filling your jars is to release trapped air bubbles between the food pieces. This may seem unimportant, but air bubbles can play havoc with your final product.
Jar seals: Too much air in the jar from trapped air bubbles produces excessive pressure in the jar during processing. The pressure in the jar is greater than the pressure outside the jar during cooling. This imbalance interferes with the sealing process.
Liquid levels: Air bubbles take up space. When there’s trapped air between your food pieces before you seal the jar, the liquid level in the jar drops when the food is heated. (For releasing air bubbles, see Figure 3-3.) In addition, floating and discolored food results from packing your food without the proper amount of liquid in the jars. Snuggly packed food eliminates air and allows enough liquid to completely cover the food with a proper headspace (refer to Figure 3-2).
FIGURE 3-3: Releasing air bubbles from your filled jars.
Choosing the right canning method and following proper procedures
Always use the correct processing method for your food. Process all high-acid and pickled food in a water-bath canner. Process all low-acid food in a pressure canner. To find out how to determine whether a food has a low or high acidity level, head to the next section. (You can find out about the different canning methods in Chapters 4 and 9.)
In addition to choosing the right canning method, follow these guidelines to guard against food spoilage:
Never use a pressure cooker as a presser canner. They are two different appliances.
Don’t experiment or take shortcuts. Use only tested, approved methods.
Never use an outdated recipe. Look for a newer version. Do not update the directions yourself. Check the publishing date at the beginning of the recipe book. If it is more than 5 years old, find a newer version.
Safe recipes are based on science, not hearsay. If you truly want to use a recipe you find online with no science to back it up, look for an approved version elsewhere.
If your elevation is higher than 1,000 feet above sea level, make the proper adjustments in processing time and pressure for your altitude. See the section, “Adjusting for Your Altitude,” for information on altitudes and processing times.
If you’re pressure canning, allow your pressure canner to depressurize to 0 pounds pressure naturally; don’t take the lid off to accelerate the process.
Allow your processed jars to cool undisturbed at room temperature.
Process your filled jars for the correct amount of time and, if you’re pressure canning, at the correct pressure (both will be stated in your recipe). Make adjustments to your processing time and pressure for altitudes over 1,000 feet above sea level.
Test each jar’s seal and remove the screw band before storing your food.
Checking your equipment
To prevent spoilage, your equipment must be in good shape and working properly:
Have
