Preserving Heirloom Tomatoes: Canning Techniques

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Food safety experts advise canning tomatoes carefully to avoid spoilage and food poisoning, since even high-acid varieties of tomato plants produce lower-acid fruits under some circumstances. Always add lemon juice or citric acid as a preventive measure against botulism risk.

Control spoilage by processing filled jars with heat in either a boiling water canner or pressure canner. Only select disease-free vine-ripened firm tomatoes without cracks or bruises before canning. Damaged or overripe tomatoes should never be canned and dead vine tomatoes could contain lower acidity levels so be wary about picking these from dead vines; freeze instead.
Assist in sterilizing new canning lids by placing them in a saucepan and simmering them in water.
Crush tomatoes using the hot pack method by peeling, removing cores, quartering them and rapidly heating in a large kettle over an even heat source; simmer for five minutes then use wooden spoon to crush.
Add two tablespoons of lemon juice per quart canning jar, and fill with hot tomatoes, before seasoning with one teaspoon of canning salt and sealing with two-piece lids. Boil water bath canning will take 50 minutes.
Process raw tomatoes packed in water using either a dial gauge pressure canner for 20 minutes at 6 pounds pressure or 15 minutes at 11 pounds. Alternatively, weighted gauge canners can take 20 minutes at 10 pounds pressure and 15 minutes at 15 pounds pressure for whole or halved tomatoes packed in water.

Add two tablespoons of bottled lemon juice to each clean quart canning jar and fill with raw whole or halved tomatoes, covering them with hot water before wiping off any residue from jar lips with damp paper towel. Adjust pretreated lids and securely screw ring onto jar before processing as directed above.
Process quart jars in a boiling water bath canner for 50 minutes. In a dial gauge pressure canner, process for 15 minutes at 6 pounds pressure or 10 minutes at 11 pounds pressure, respectively. With weighted gauge canners, use 15 minutes at 10 pounds pressure or 10 minutes at 15 pounds pressure as processing times.
Raw whole or halved tomatoes packed in juice: (To prevent spoilage, tomatoes packaged in juice require longer processing times.)

Add 2 tablespoons of lemon juice and 1 teaspoon of salt per quart jar, then fill with peeled raw tomatoes, pressing or straining as necessary, or using previously prepared hot juice as an alternative source. Wipe off the lip of each jar using damp paper towel before adding pretreated lids with screw rings onto them for storage.
Process quart jars for 90 minutes in a boiling water bath canner. In a dial gauge canner, allow 40 minutes at 6 pounds pressure or 25 minutes at 11 pounds; with weighted gauge canners you should allow 40 minutes at 10 pounds pressure or 25 minutes at 15 pounds pressure for processing times.

* Avoid spoilage by heat processing filled jars in either a boiling water canner or pressure canner. * For optimal results, only select disease-free, vine-ripened firm tomatoes without signs of damage or overripeness and do not process them with other tomatoes that might contain lower amounts of acidity; these should instead be frozen instead.
* To help sterilize new canning lids, place them in a saucepan with boiling water and set it on low to ensure complete sterility.

Crushed tomatoes using the hot pack method: * Peel, remove cores, quarter and heat quickly in a large kettle before simmering gently for 5 minutes and crushing with wooden spoon.
* For each clean quart canning jar used to store hot tomatoes add two tablespoons of bottled lemon juice as well as one teaspoon of canning salt before filling them up and sealing using two-piece canning lids only (this ensures maximum productivity! ).
* Process quart jars in a boiling water bath canner for 50 minutes. In a dial gauge pressure canner, process for 20 minutes at 6 pounds pressure or 15 minutes at 11 pounds pressure, or use weighted gauge canner with 10 or 15 pounds pressure as per manufacturers recommendations.

Whole or halved raw tomatoes packed in water:
* Add two tablespoons of bottled lemon juice to each clean quartcanning jar and fill it with raw whole or halved tomatoes, adding two more tablespoons if necessary, before covering with hot water and wiping off jar lip using damp paper towel. * Secure pretreated lids to the jar by screwing on its ring lid securely.
* For best results, process quart jars for 50 minutes in a boiling water bath canner.
In a dial gauge pressure canner, process for 15 minutes at 6 pounds pressure or 10 minutes at 11 pounds pressure; with weighted gauge canners you should process for 15 minutes at 10 pounds pressure or 10 minutes at 15 pounds pressure respectively.

Raw whole or halved tomatoes packed in juice require additional processing steps in order to avoid spoilage, such as adding two tablespoons of lemon juice and one teaspoon of salt per quart jar before filling with peeled raw tomatoes.
* To create enough juice to cover, or to add to previously strained hot juice.
Wipe off jar lips with damp paper towel before wiping off infected areas with detergent solution and disinfecting with alcohol solution. Secure pretreated lids and screw rings onto jars prior to processing for 90 minutes in boiling water bath canner.
* In a dial gauge canner, process for 40 minutes at 6 pounds pressure or 25 minutes at 11 pounds. In a weighted gauge canner, process for 40 minutes at 10 pounds or 25 minutes at 15 pounds pressure.

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