Home Canning

Home canning is an important method of preserving food which became possible after the American John Landis Mason invented the mason jar in 1858. A mason jar is a practical glass jar which has a rubberized metal disk which seals the jar's contents.  

Food is cooked first. Then together with the liquid in which it was cooked, it is poured into a clean, hot mason jar. The mouth of the jar is covered with a metal disk that has a rubber ring seal. A screw-type lid is partially screwed onto the glass jar. The jar is then heated in boiling water for a certain period of time, and the screw top will be tightened completely. This is because the heat and pressure during the boiling process force most of the air out of the jar which reduces the danger of bacterial growth. This method is known as the hot -pack method.  

Another method of using the mason jar in canning food is called the open-kettle method. Usually jams and jellies are prepared by this method. The jam is cooked and then poured into hot, sterilized jars. Then the jars are sealed and no further heating is necessary. The sugar used in preparing jams and jellies serves as a preservative.