05 September 2011

How to Preserve Vegetables and Fruit

There are many different methods for preserving fruits and vegetables.  As your gardens overflow and you wonder if you can eat all the bountiful harvest, home food preservation is a great way to capture it all for use later in the season.  It is also a fun activity for the entire family and everyone will be proud of their accomplishments! 

There have been many methods used for preserving food over the years.   Many older methods have since been deemed to be unsafe and now, only several methods are recognized as safe.  They are the boiling water method, the pressure method, freezing and dehydrating. 
The boiling water method is used to process high-acid foods at a temperature of 212°F for the period of time specified by the recipe used.  This method is used to destroy molds, yeasts, and certain bacteria as well as to de-activate enzymes which could spoil the food.  The boiling water method should not be used to process low acid foods as the temperature would not be high enough to kill certain bacteria and their toxins which could cause botulism.

The pressure canning method utilizes a pressure canner.  In order to destroy bacteria and spores that could potentially produce toxins, low-acid foods must be processed at a temperature of 240°F and held at that temperature for the time specified by the recipe.  There are two different types of pressure canners.  Pressure canners fitted with a dial gauge must be tested for accuracy every year and must be monitored during the entire processing period to ensure the proper temperature is being maintained.  Pressure canners fitted with a weighted gauge do not need to be tested for accuracy but should the gauge be damaged in any way, the gauge must be replaced prior to use.
Generally, most recipes are written for use at altitudes at or below 1000 feet above sea level.  Because barometric pressure is reduced at higher altitudes, it changes the temperature at which water boils.  Both methods of canning would need to be adjusted to take this increase in altitude into consideration.  The Ball Blue Book® Guide to Preserving has a chart showing the necessary adjustments.

Another method of food preservation is freezing.  Most frozen vegetables may be stored for up to one year.  The fresher the vegetable, the better the quality product you will end up with.  Vegetables being frozen must first be blanched.  Blanching is critical to remove surface dirt and microorganisms, brighten the color of the vegetables, retain vitamins and reduce the action of enzymes which might otherwise destroy the freshness and flavor after just four weeks of storage.  Blanching is done by lowering the selected produce into boiling water for the amount of time specified by the recipe. 
Dehydrating food is probably the oldest method of food preservation.  It is very simple to do but does not follow exact methods, so some trial and error processes may be necessary.  Drying times will vary based on any given day’s climate.  Most vegetables and some fruits benefit from pre-treatment prior to dehydrating, such as blanching vegetables for the same reasons mentioned earlier, or dipping fruits to prevent browning.

The Ball Blue Book® Guide to Preserving includes directions for all of these methods, pre-planning tips and many, many recipes.