There are several types of home food preservation aimed at converting food into a state that will allow it to be stored for a long time without spoiling while maintaining some elements of the original texture and flavor. Some very popular methods, such as canning and pickling, are easily accessible to anyone with the time. Other methods, such as dehydration, freeze drying, fermentation and salting require advanced knowledge and sometimes special equipment to perform correctly. All of the methods used for home food preservation use some technique to ward off harmful bacteria and prevent it from spoiling food.
One of the most important aspects of home food preservation is preventing bacteria and other harmful organisms from reaching the food and causing it to spoil. Each home food preservation technique addresses this in a different way, sometimes through managing the moisture content of the food, sometimes by changing the acidity, and other times by creating a physical barrier to stop the bacteria. The success or failure of the techniques are tied to maintaining very precise conditions throughout the process, meaning that it is important to prepare ingredients for preservation according to tested techniques, because variations in the procedure can lead to unpredictable and sometimes harmful results.
Canning involves taking food that has been prepared, sometimes through cooking, and placing it in a sterile container filled with liquid. Glass jars with specially fitted lids are commonly used. The jars are sterilized and filled with food that is clean and a liquid or brine. The filled jars are closed and boiled or exposed to pressure to seal them tightly, preventing bacteria from entering the can to ruin the food. Nearly anything from meat to vegetables can be canned, allowing them to be preserved for a year or longer.
Using pickling as a home food preservation method means relying on a brine of salt to fight bacteria. Pickled foods sometimes have to be refrigerated and do not always last as long as some other methods. Meat and vegetables are commonly pickled, although items such as eggs and sausages also can be pickled. The change in acidity in the brine and the strength of the salt keeps the food preserved, although it will also change the taste and texture over time.
Dehydration can be used to reduce the moisture content in foods. When used for home food preservation, a lack of moisture means bacteria will have nowhere to take root, allowing food to remain edible for a much longer time. Fruits, some vegetables and some meat can be dehydrated and then either eaten dry or reconstituted later with water. The process can be performed with a special dehydrating machine or through open-air drying in controlled conditions.
Fermentation of foods can be used for home food preservation. This involves allowing beneficial bacteria to interact with food in a way that creates elements such as lactic acid, forming a hostile environment for harmful bacteria. Depending on the type of fermentation, the food can be stored for a long time in the correct conditions, sometimes allowing the fermentation to continue. Other techniques stop the fermentation process and then can the food for long-term storage.