According to Martha's mother, Martha Kostyra, who loves to can her fruits and vegetables, the key to successful canning is using fresh produce, whether from the garden or the market. Firm, ripe fruit is best processed within hours of picking; if you cannot process fruit for a day or two, be sure to refrigerate it. Also, try not to use "drops" -- fruit or vegetables that have fallen from trees or bushes -- as these may have begun to decompose and will produce less than ideal results. Following, some tips for canning at home.
It is very important to have clean utensils, cloths, and work surfaces, including cutting boards and countertops. Jars and lids must also be absolutely clean; lids must be free of dents. Use flat-lid seals only once, and reuse screw-top lids only if they are rust-free and not bent. Begin by assembling and cleaning your equipment. Wash jars, lids, and screw tops in warm, soapy water, and rinse thoroughly. You will also need a jar lifter, a stainless-steel funnel, a strainer, and an additional saucepan for cooking your produce.
Place clean flat-lid seals and empty jars standing upright on the rack inside your canning pot, and fill the pot with water to a level 1 to 2 inches above the rims of the jars. (To prevent flat lids from floating, place them underneath the jars before filling the pot with water.) Bring water to a simmer. Jars must simmer at 180 degrees for a minimum of 10 minutes before they will be ready to use.
Follow the recipe exactly. You cannot substitute other fruits or vegetables, because the sugar-to-acid ratio must be precise. Wash all fruits and vegetables thoroughly, but do not soak them. Remove the stems, hulls, pits, skins, and cores (according to your recipe instructions), and cut away all soft or bruised spots, as well as any places where the skin is broken.
Always cook fruits and vegetables in a nonreactive (stainless steel or enamel) saucepan. This is important because some substances can react with food, giving it an unpleasant metallic taste.
Use the jar lifter to take a jar from the hot-water bath. Pour out any hot water from the jar. While the jar is still wet and warm, put a stainless-steel funnel in its mouth. Ladle in hot jam, or whatever you are canning, making sure to leave the amount of "head space" specified in your recipe. This space is essential to achieving a proper seal. Wipe jar lip with a clean, damp cloth to remove spillage. Using a pair of tongs, lift a flat-lid seal from the rack; place it on the jar, and secure the screw top.
Boiling Water Bath
This process will sterilize your jars. Using the jar lifter, lower a filled jar into boiling water, and rest it on the rack in the canning pot. Place jars 1 inch apart, away from the sides of the pot. Repeat this procedure, one jar at a time, until all jars are filled and covered by 1 to 2 inches of water. Again, the 1- to 2-inch level is crucial in order to achieve a proper seal. Cover the pot, and keep it at a full boil for the time specified in the recipe. Remove jars with lifter; cool for 24 hours on a wire rack.
Before putting the cooled jars away, test each seal. Press the center of the lid; it should stay rigid. Or remove the screw top, grasp the edges of the lid, and lift. If the lid flexes or comes off, store the food in the refrigerator, and use within 1 week. If the seal is good, label the jar, and store it in a cool, dry place for up to a year.
If you find any of the conditions listed below after the jars have been stored away, destroy the contents so they will not be eaten by people or animals, and discard all metal lid seals.
- Broken seals, bulging lids
- Mold in contents or around seal or underside of lid
- Small bubbles in contents
- Spurting liquid, caused by pressure from the inside as jar is opened
- Off odor, mustiness
Learn more about canning with Jeanne Lesem's "Preserving in Today's Kitchen: Easy, Modern Canning Methods -- with 168 Recipes" and Janet Greene, Ruth Hertzberg, and Beatrice Vaughan's "Putting Food By."