The canning process was invented in the 1800s in France by Nicolas Appert. During this time, Napoleon was in the middle of his conquest of Europe and needed a way to supply his troops with food that could be preserved cheaply in large quantities. Appert discovered that food sealed in glass jars did not spoil unless their seals were broken. Modern canning today for the home cook is much the same as in those days, albeit with better jars and seals. The term “canning” is a bit of a misnomer since no cans are involved. Instead, home canning is done strictly with glass jars.
Strawberries, red, sweet, and luscious, reach their optimum in the summer. The best way to preserve their exquisite flavor is to freeze them quickly on a sheet pan in a single layer. From there, they can be packaged into freezer bags. Canning strawberries is another option, although it presents some problems. For one, strawberries have extremely high water content. This make canning strawberries directly, as one might do with sturdier fruits like peaches, difficult. The high water content and the canning process often leave the end results looking like a chunky, soupy mess as the berries disintegrate. Instead, a better way to can strawberries is to turn them into jams or preserves.
Strawberries should only be washed right before use because they will absorb a lot of water and yield poor results. In order for strawberry jam or jelly to set, pectin must be added. Pectin is a natural gelling agent that is found in some fruits such as apples. Pectin combines with the sugar in the jam to produce the jelly-like texture. For this reason, jams and jellies often have high sugar contents. Recipes all differ, so it is important to follow the proper proportions of fruit to pectin to sugar in order to have successful results. In recent years, methods have been developed that eliminate the need for pectin. Often the addition of a high pectin fruit such as an apple can help a pectin-free jam to set. Other recipes cook equal parts of sugar and fruit by weight until the mixture thickens to the proper consistency. This method produces a jam, but without the pectin, it will not have the familiar jelly-like quality that those made with pectin produce.
Once the jam or jelly has been cooked, the canning process can begin. Canning at home is done either in boiling water or in a pressure canner. Foods that are low in acidity like meats need to be pressure canned. Those with a high acidity like most fruits can be canned in boiling water. Strawberries are low in acidity and can therefore be canned without the use of a pressure canner. The first rule of canning is to keep all surfaces that will come in contact with the jam sterile. The first step in the sterilization process is to sterilize the jars. The jars are placed into a canning pot on a rack so that they don’t rattle on the bottom of the pot. After that, water should be added to the pot until it reaches a level of at least one inch above the rim of the jar. The jars should be boiled on high temperature for at least 10 minutes. Tongs and funnels should be sterilized in this manner as well and can be placed in the pot at the same time as the jars. The lids should also be boiled but not as long. Filling the prepared jars should be done while the jam mixture is still near the boiling point. The rim should be wiped clean to ensure a tight seal and then the lid should be placed on. Next, it is important to screw the top on, making sure that it is firm but not too tight. The filled jars should now be placed into the canner, which should be filled with water 2 inches above the jars. The pot should be brought to a boil for at least 10 minutes. After 10 minutes, the jars can be removed. A distinct popping noise will be heard as the jars cool that signify that the lids have sealed properly.
Having fresh strawberry jam year round is something that every home cook can achieve. Proper canning methods need to be followed, though, to prevent illness. When in doubt, it is important to follow the directions that come with the canner as well as the recipe.