Most vegetables should be processed within six to 12 hours after being picked. Apricots, nectarines, peaches, pears and plums should be ripened one or more days between harvest and canning. Spread in a single layer on a clean dry surface to ripen more evenly. If the canning of fresh produce must be delayed, keep it in the refrigerator if possible, or in a cool, dark place. Recommended processing times should be followed because proper canning practices remove oxygen from food tissues, destroy enzymes, prevent the growth of undesirable bacteria, yeast and molds, and help form a vacuum in jars.
Good vacuums form tight seals that keep liquid in and air and microorganisms out.
If proper canning practices are not followed, chances increase for the of the survival of Clostridium botulinum , the bacteria that causes botulism, a deadly form of food poisoning. These bacteria exist either as spores or as vegetative cells. Botulinum spores, which are similar to seeds, are on most fresh food surfaces. The spores can survive harmlessly in soil and water for many years. However, when ideal conditions exist for growth, they produce vegetative cells that multiply rapidly.