• Canning is used most widely for preserving fruits and vegetables.canned fruit image by dwags from Fotolia.com
  
  Canning, along with drying, is one of the oldest methods for preserving food. Canning is most common in the northern hemisphere where year-round fresh items such as fruits and vegetables aren't prevalent. For such historical reasons, canning is nearly non-existent in the culinary cultures of southern hemisphere nations. There are a wide variety of commercial uses for canning as well as specific canning uses that can be done in the home.
  
  

Fruits

• Fruits are one of the most common uses for canning. As fresh fruits are extremely scarce during the winter seasons of norther cold climate regions, people started to can them as a way to store them so that they could be readily used throughout the fruit-less winter months. The name "preserves" referring to fruit jam is literally what it is; preserved fruits. The canning of fruit is used to make jams, jellies, marmalade and even whole fruits such as whole pears, plums, cherries and apricots. In most jams and fruit preserves, sugar is added not as a preservative but as a flavor and color enhancer, so it is not a necessity in canning fruits. Tropical fruits do not can well as they have very little natural pectin. The most commonly canned fruits are apples, pears, grapes, tomatoes, berries and stone fruits including peaches, plums, apricots and cherries.
  
  

Vegetables

• Vegetables were often canned for the same reasons as fruit; to have available vegetables during the winter months. The preservation of vegetables, however, is much different than fruits. Most canned vegetables are preserved by pickling in a vinegar-based brine. Pickled vegetables include cabbage, cucumbers (pickles), onions, green beans, beats, radishes, carrots, asparagus and any other vegetable that can withstand the pickling process. Most pickling brine consists of vinegar, spices and salt. Pickling is the safest way as it involves high levels of acid which help to prevent growth of deadly bacteria.
  
  

Sauces and Spreads

• Since the days of pure preservation, canning has moved on to gourmet and specialty items including sauces and spreads. Chutney, spaghetti sauces, ketchup, mustard, salsa, hot sauces, barbecue sauce, relish and even bean dips can be canned. With the same type of canning equipment used to preserve vegetables and fruit, any of theses sauces, spreads and condiments can easily be canned at home. The key with sauces and spreads is that they contain a high acid content which is necessary for canning to prevent the bacteria botulinum from growing. Home canning of oil-based items such as hummus or salad oils is not recommended because there isn't a large presence of acid.