Tomatoes in jars (Appert method)
Nicolas Appert invented canning in 1810 to feed Napoleon's armies. Two centuries later, opening a jar of tomatoes in the depths of winter is still to find the exact taste of a July sun.
Jar sterilisation (the Appert method) is the preservation technique par excellence: you fill jars, heat them to a high temperature in water to kill all micro-organisms, then the cooling creates an air vacuum that seals the contents. For the tomato, acidification is crucial: it is what secures it against botulism.
Ingredients
- Ripe, healthy tomatoes (Roma, Marmande, San Marzano)1.5 kg
firm but well red, no green or damaged areas
- BOTTLED lemon juice (stable acidity), or citric acid2 tbsp per 1 L jar (i.e. ≈ 4 tbsp in total)
ESSENTIAL for safety, not an option: BOTTLED juice (standardised acidity), never fresh (variable acidity). Alternative: food-grade citric acid. Dose and type follow the NCHFP/USDA protocol.
- Fine salt1.5 tsp
- Sugar1.5 tsp
optional, slightly softens the acidity
- A few leaves per jar
Equipment
- •2 Le Parfait rubber-seal jars of 1 L (screw-top jars are not suitable)
- •1 large tall pot (steriliser) with a lid
- •1 clean cloth
- •1 cooking thermometer (very useful)
Steps
- 1
Prepare the tomatoes
Wash the tomatoes. You can peel them (a cross incision at the base, 30 s in boiling water, then an ice bath, the skin comes off on its own) or leave them whole with the skin. Keep them whole if small, or cut them in half or into quarters depending on size.
30 min
- 2
Prepare the jars
Wash jars, lids and seals in very hot soapy water, then scald the jars and lids for 10 min (never the rubber seals, which would melt in the oven, but which can be briefly scalded). Fill them while still hot.
20 min
- 3
Fill the jars
First pour the acid dose straight into each 1 L jar: 2 tbsp of bottled lemon juice, or ½ tsp of citric acid. This is the anti-botulism guarantee, never to be reduced. Mix the tomatoes with the salt and sugar, then pack them into the jars, pressing lightly so they release their juice, to 2 cm from the rim. The tomato juice must cover the pieces. Add a basil leaf if you like. Close with the clean seal and the lid.
15 min
- 4
Sterilise in a water bath
Place a cloth at the bottom of the pot (to stop the jars knocking together). Place the jars. Fill the pot with water up to the neck of the jars (the jars must be covered with water). Cover the pot. Bring SLOWLY to the boil (at least 1h30, this gradual rise is crucial so the jars don't crack).
1h30 to come to the boil
- 5
Maintain the cooking
Once the water is boiling, keep a FULL BOIL (large bubbles, 100 °C, never a mere simmer) for 30 minutes for whole tomatoes, 40 minutes for tomatoes cut in half or quarters. Never let the water drop below boiling during the count.
30 to 40 min
- 6
Cool and check
Turn off the heat. Let the jars cool in the pot water (don't take them out abruptly, thermal shock = a cracked jar). Once lukewarm, take them out and let them cool completely in the open air. Check the seal: unlatch the lid (without removing it); if it stays hermetically closed by the vacuum, it's perfect. Otherwise, eat quickly and keep cool.
Several hours
Storage
1 year in a cool cupboard (15 °C ideal), dry and dark. Label with the date.
How to use it
The base of all tomato sauces, pizzas, stews. To open and heat like an industrial can, except it's your tomato, your sun. A 1 L jar = a base for 4 people.
Health properties
- Lycopene (red pigment), its bioavailability increases with cooking, so canned tomatoes paradoxically contain more of it than fresh ones
- Vitamins A, C, K preserved (the C in part)
- More economical than industrial cans, and without BPA or additives
These preparations belong to cooking and herbal tradition: they nourish and support, do not “cure” anything and replace no treatment. Ask a doctor or pharmacist before prolonged use, if under treatment, pregnant or breastfeeding, or for a child. Follow the stated storage precautions strictly.
Precautions
BOTULISM RISK, the tomato is right at the safe acidity limit (pH ≈ 4.6). Acidification is NOT OPTIONAL: it follows the NCHFP/USDA protocol, at the dose in step 3, with citric acid or BOTTLED lemon juice, never fresh juice whose acidity varies. A smaller dose does not guarantee safety, and the 100 °C water bath does not destroy the bacterium's spores. Never sterilise other low-acid vegetables (beans, squash, asparagus) with this water-bath method, they need an autoclave/pressure steriliser. ALWAYS check for bulging, a fermented smell or gas escaping on opening, at the slightest doubt, discard without hesitation. Do not reuse the rubber seals from one batch to the next.
Sources & tradition
- · Method of Nicolas Appert (1810), the invention of sterile canning
- · USDA Complete Guide to Home Canning, modern safety protocols
- · L'autosuffisance, c'est possible ! (Cherche-Midi)
- · Center for Food Safety (NCHFP), on the acidification of tomatoes