Canning is defined as the process of preserving fruits or vegetables in order to pro-long their shelf life. You can preserve tomatoes using the canning process. This is done by placing the tomatoes in jars and given heat treatment to destroy micro-organisms that would otherwise spoil the food. The jar is vacuum sealed with this process, sealing the tomatoes from air contact that can cause contamination.
Basic process for canning your tomatoes
There are two safe methods for canning tomatoes: boiling-water-bath and pressure canning. Foods with pH value above 4.6 must be processed by pressure canning to insure food safety. Food with a pH value of 4.6, or lower, may be processed with the boiling water bath method. The tomatoes can be canned as juice, sauce, whole, stewed or chopped. Tomatoes are high acid foods. High acid levels prevent the growth of Clostridium botulinum bacteria which is heat resistant. The boiling-water-bath method which is done at 212°F also destroys common forms of spoilage microorganisms such as mold and yeast.
When canning tomatoes with the boiling water bath method, you should make sure that the acid level is low by adding 1 tablespoon of lemon juice or 1/4 teaspoon citric acid per pint of product. Add this directly to the jars before filling in the tomatoes.
Selecting Your Tomatoes
Always use fresh ripe tomatoes that has the least blemish (blemish free is best). Do not use tomatoes that are too ripe or too soft. The best type is one straight from your own garden or at a farmer\’s market. Store the ripe tomatoes that are to be canned at room temperature, away from sunlight and not in a fridge. To know how much tomato you should use, refer to the table below for an approximate value of tomatoes that you can use for the desired results.
Quantity of Fresh Tomatoes per Quart
Quantity per Quart
Tomatoes (whole, stewed, or chopped)
2 1/2 to 3 1/2 lbs.
Tomatoes (for juice)
3 to 3 1/2 lbs
Preparing the Tomatoes
- Clean the tomatoes of any grit or dirt. Remove any blemishes present and throw away any over ripe or spoiled tomatoes. Then wash them under cool running water.
- Make an “X” cut at the bottom of each tomato with a knife.
- Fill a saucepan with water and bring to boil. Set aside a bowl of cold water next to where the saucepan is so that you can transfer the tomatoes from saucepan to bowl easily.
- Place tomatoes into boiling water for about 30 to 60 seconds.
- Fish them out then place into cold water.
- Core the tomatoes and peel away the skin carefully.
- The tomatoes are then ready to be canned whole or cut.
These tomatoes are then ready to be canned either with hot packing or raw packing (cold packing method) with the boiling-water-bath or pressure canning process. Hot packing is done by boiling the tomatoes and simmering them for 2-5 minutes. They are then immediately packed in a canning jar, covered with hot water (boiled), with 1/2 inch headspace in the jar. Raw packing is done by placing raw in canning jars with proper headspace. They are then covered with boiled water.
If you\’re unsure of which method to use, it is always safer to use the hot packing method.