Canning 101: Acid Foods

Canning 101:  Acid FoodsFor successful gardeners canning is more than just a hobby.  Canning is a passion to preserve every crumb of the summer harvest while vegetables are at their succulent peak and most bountiful.  Homegrown canned food may be enjoyed all year round or given as gifts to friends and family.

Food Acidity

Fruit and vegetables need to be processed according to their PH level.  Food that is high in acid will need less heat and processing time than food with a low amount of acid.  Food that is processed safely by boiling must have a PH level of 4.6 or lower.  The lower the PH level, the more acid the food contains.  Most fruits are high enough in acidity for this type of processing, along with almost all types of tomatoes.  A large selection of vegetables can be processed by the boiling method when lemon juice, vinegar, or pickling agents are added.

Materials used for Canning

The glass jars used for canning are called mason jars.  They typically come in either pint or quart sizes.  The jars may be reused.  The lids are made out of two parts.  A flat disc like piece with a rubber edge is used for the top.  This part of the lid is designed to be sucked in to create the seal.  The other component of the lid screws around the top edge of the mason jar and helps to secure the lid.  Lids can only be used once because they warp and bend after processing.  The screw on band may be used again if it shows no visual damage or change in shape.  A large stockpot or canning pot is used to boil the mason jars.

Prepping Fruit and Vegetables

Never use anything made out of aluminum or untreated cast iron for slicing, stirring, spooning and cooking the food that you prepare for canning.  Metals will cause unwanted chemical reactions in food even after it is processed.  Use glass or plastic cookware instead.

Select fruit and vegetables that are ripened to their full color and are slightly firm.  Do not use completely ripened or softer fruits.  Discard fruit with any hint of rot and disease.  If you are canning tomatoes, you may want to add citric acid or lemon juice to ensure that there is enough acidity.  Syrup and pectin are helpful for upholding the color and body in fruit.  Rinse and wash off the produce thoroughly before cutting into bite size pieces.  Some produce must be cooked before processing while others can be packed raw.  Check the recipe to see how to prepare the specific type of food you are canning.

Basic Canning Method

Sterilize jars in boiling water for ten minutes before filling.  Loosely pack the mason jars with the prepared food, then top off the contents with liquid according to both the manufacturer and recipe directions.  Wipe off any debris left on the rim with a sterile damp towel after filling.  Cover the jar with the lid according to recommended firmness.

Preheat the water in the canner to prevent temperature clashes that may cause breakage to the glass mason jars.  The water will need to be 140 degrees for raw vegetables.  If the contents are hot, the water will need to be 180 degrees.  When the water is preheated, carefully add the jars, making sure that they are completely submerged by the water.  Gradually bring the pot to a regular and steady boil.  Boiling time is determined by altitude.  The higher the altitude, the longer the boiling time will be needed.  Check the recipe guidelines to see how long you will need for boiling according to your area.  Generally, every thousand feet above sea level will need an additional two minutes longer.

After they have boiled for the recommended time, remove and place the jars on a steady surface covered with a towel.  Date and label each container after they are cool enough to handle.