Water Bath Canning Details

High acid foods, such as most fruits (tomatoes included) do not need to be processed under pressure because the natural acid inactivates enzymes and bacteria. While the acid in these foods has no effect on molds and yeasts, processing the jars in a kettle of boiling water is enough to raise the temperature of the food to beyond their killing point. Yeasts and bacterium are destroyed by temperatures ranging from 140o to 190oF [60o to 88oC.] Food commonly processed in a water bath is listed in the table at the end of this section.

Food canned in large pieces will require longer processing to heat it through than food that is cut small. Food that is raw and cold when packed also requires longer processing time than if it were already hot when packed. Another consideration is the size of jars used. Large jars require more time in the bath than do small jars so that all the food contains reaches the required temperature.

After the jars have cooled and been checked for a good seal, they should be stored in a cool, dark place – preferably 40o to 60oF [5o to 15oC]. Most foods kept this way will keep for up to a year.

NOTE: Any food whose odor or appearance is questionable when the jar is opened should be discarded at once. Never test it by tasting it. Botulism can be deadly!

To preserve as much of their fresh color and flavor as possible, many fruits and vegetables may be “cold packed”. The food is washed, peeled, cored or seeded just as for ordinary cooking. Most are cut to a uniform size (this must be done to ensure uniform heating of the food) and placed into the jars.

Light colored fruits (like peaches) should be dropped into water containing a bit of lemon juice to prevent the flesh from darkening. This is called ‘acidulating’. Allow one teaspoon [5ml] of lemon juice per quart [1 liter] of water. Most fruits can be packed raw. Do not allow the fruit to soak – just drop the pieces in and lift them out with a slotted spoon or sieve.

If the food was blanched, it is drained. Whether or not it was blanched, it is then packed into jars loosely and boiling water or other liquid is poured into the jar to cover the food. Remember to leave the appropriate headspace (see chart). Most canning jars, with the exception of fragile clamp-top (wire bail) jars, are then placed into already a deep kettle that already has simmering water.

After adding the jars, do not allow them to touch each other, the water is then brought to a full boil. After the water comes to a full boil, the lid is placed onto the kettle and the timer can be started. After the processing time has been accomplished, turn off the heat and lift the jars out of the kettle. Set them on a wire rack or towel to cool, leaving at least an inch of space between them.

If using clamp-top jars, these must be placed in tepid water, which is then brought to a boil, covered, and the processing time is then started. At the end of processing, the heat is turned off and the jars are removed only after the water reaches room temperature. Again, these special arrangements are because of the fragile nature of the jars.

Sugar syrups can be any strength, from very light to very heavy, depending on the amount of sugar per quart of water or juice used. Artificial sweeteners can be used in place of the sugar, however any preservative quality is unsubstantiated. Also, commercial unsweetened juice may also be used, either as is or diluted with water. Plain boiling water can also be used.

Fruits canned without sugar will be softer in texture than if sugar is used. The whole purpose of the liquid is in eliminating air, so make sure to remove any air pockets, particularly when canning such things as peach halves. The cavity where the pit resided needs to be faced up so that air is not caught in it. If desired, the table below shows the different strengths of sugar syrups. The water and sugar are boiled together in a pan until the sugar is completely dissolved, about five minutes.

Water Bath Canning Charts