Canning & Preserving For Dummies. Amelia Jeanroy

results as long as you follow the proper steps and procedures for preparing, processing, and storing your food.

      Before you begin your canning and preserving journey, take a stroll through this chapter, which introduces you to microorganisms, enzymes, and other potentially dangerous situations that cause food spoilage. You can also find information on how to prevent and identify food spoilage. The technical portion of this chapter shouldn’t deter you from canning. Rest assured, after reading this information, you’ll have no fear about preparing and serving your home-canned and home-preserved food.

Dispelling Your Fears of Home-Canned and Home-Preserved Food

      Preventing food spoilage is the key to safe canning. Over the years, home-canning has become safer and better. Scientists have standardized processing methods, and home-canners know more about using these methods. When you follow up-to-date guidelines exactly, you’ll experience little concern about the quality and safety of your home-canned and home-preserved food.

      The following sections offer some tips for safely handling, preparing, and processing your food.

      Preparing your food properly

Prepping to start canning and preserving can sometimes feel daunting and keep you from starting. The truth is, getting your food ready is only a matter of basic science and common sense. None of these steps are difficult. For example, use fresh, firm (not overripe) food. Wash and prepare your food well to remove any dirt and bacteria: Wash it in a large bowl filled with room temperature water and a few drops of dish detergent, and then rinse it in a separate bowl of fresh water (see Figure 3-1). Can your fruit and vegetables as soon as possible after they’re picked. Wash only the type of food you are going to be preserving each time. To avoid cross contamination, do not mix different foods during this step.

      FIGURE 3-1: How to wash fruit and vegetables well.

      

No, you don’t have to wash berries individually: Put them in a colander and submerge the colander, berries and all, in the wash bowl; then rinse them off with a running spray of water.

      Packing 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.

      

Headspace is also important when you’re freezing food because frozen food expands during the freezing process. If you fail to leave the proper headspace in your freezer container, the lid may be forced off the container, or the container may crack or break. When your frozen food comes in direct contact with the air in your freezer, the quality of your food deteriorates, and the food develops freezer burn (go to Chapter 13 for more on freezing food). On the other hand, too much air space allows excess air in your container. Even though your food doesn’t come in direct contact with the air in the freezer, the excess space in the top of the container develops ice crystals. When your food thaws, the excess liquid reduces the food’s quality.

      

If you don’t trust yourself to eyeball the headspace, use a small plastic ruler (about 6 inches long) to measure the correct headspace in the jar.

      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.

Repeat after us: Never skip the step of releasing air bubbles.

      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