Sterilizing jars is the first and most important step. If your jars are not sterile, you won't preserve anything.
Jars should be free of any chips or cracks. Preserving or canning jars are topped with a glass, plastic or metal lid, and require a rubber seal. Two- piece lids are best for canning, as they vacuum-seal as they cool.
To ensure everything is sterile, wash jars and lids with hot, soapy water. Rinse well and arrange jars and lids, open side up and without touching, on a tray. Set oven to 175°F and heat jars and lids for 25 minutes. Or, boil the jars and lids in a large saucepan, covered with water, for 15 minutes.
Use tongs when handling the hot sterilized jars. Be sure the tongs are sterilized too, by heating the ends in boiling water for a few minutes.
As a rule, hot preserves go into hot jars and cold preserves go into cold jars. All items used in the process of making preserves must be clean. This includes any towels used, and especially your hands.
Some recipes call for a boiling water bath, which is used in canning acidic foods like pickles, tomato sauce and preserves. The boiling water bath eliminates any airborne microorganisms present in the pickling jar while it is being filled and sealed, and forces the air out if the food and canning liquid, creating a vacuum and perfect seal that prevents spoilage. Processing in a boiling water bath for preservation longer than a few weeks is definitely not optional and should be done with care.
Boiling water baths are sold commercially and are quite reasonably priced as a kit. I suggest you use them. Once filled, the jars must fit in the pot on the rack with 1-inch space at the bottom and enough room at the top to cover the jars by two inches. This allows the water to flow freely around the jars. It is important to remember never to tighten the lid before processing or the air will not be able to escape, and the lid won't seal. Remember it is not you that is making the seal but the jar itself; as the contents of the jar and the air space at the top shrink, the lid is sucked down firmly onto the rim.
Check the seals after one day. A concave lid indicates a proper vacuum. If the lid clicks up and down when pressed, the seal is not complete. You will have to start again.
Excerpted from Earth to Table by Jeff Crump and Bettina Schormann Copyright © 2009 by Jeff Crump and Bettina Schormann. Photographs Copyright © 2009 by Edward Pond. Excerpted by permission of Random House Canada, a division of Random House of Canada Limited. All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.