Tomatoes in jars, step by step

1. Tomatoes for jars

Only sound, ripe, firm tomatoes go into a jar.

1. Meaty plum tomatoes — Long Roma and San Marzano types have few seeds and little water and give a thick sauce with shorter cooking. For whole tomatoes, choose smaller plum tomatoes of even size.
2. Large ones for juice — Round, large tomatoes such as beefsteak give more juice, but sauce made from them takes longer to cook.
3. What stays out of the jar — Not from wilted vines, not after frost, not overripe, soft or split. Tomatoes with rotten spots or mould go on the compost.
4. How many tomatoes — For 1 L you need roughly 1.5 kg for juice, 1.4 kg for whole tomatoes, 2.3 kg for passata and 3 kg for thick sauce (1 kg ≈ 2.2 lb). Jars of 500 mL, 720 mL or 1 L (pints and quarts), new lids.

Why: Tomato acidity sits around the pH 4.6 line and changes with variety, ripeness and weather. Overripe tomatoes, tomatoes from wilted vines and tomatoes picked after frost are usually less acidic.

• Green tomatoes aren't for sauce: they go into pickles (H43-03).
• Meaty plum tomatoes give up to a quarter more. Write your own figures in the batch log.

2. Acid in every jar

You don't add acid “when the tomatoes are sweet”, but always, to every jar.

1. Citric acid — 2 g of citric acid (½ teaspoon) per 1 L of tomatoes, 1 g per 500 mL. At the start of the season weigh it into small envelopes: one 2 g envelope for every 1 L jar.
2. Or bottled juice — Instead of citric acid, 30 mL (2 tablespoons) of bottled lemon juice per 1 L, or 15 mL per 500 mL. Bottled juice has a standard acidity.
3. Vinegar and scales — Vinegar 5 % is allowed, 60 mL per 1 L, but it changes the taste more. To weigh 1 g of acid you need kitchen scales accurate to 0.1 g, not a guess.
4. Into the empty jar — Put the acid into the empty jar before filling, or when the jar is half full. That way it is sure to be distributed.

Why: Tomatoes with a pH above 4.6 are not safe from botulism in a boiling-water bath. A little citric acid or bottled lemon juice per jar solves the problem and doesn't change the taste much.

• Don't replace bottled lemon juice with fresh lemons: fresh lemons vary in acidity.
• If the acid bothers you in the taste, add a teaspoon of sugar per jar.

3. Peeling and the hot break · Locked

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4. Juice and sauce · Locked

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5. Filling · Locked

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6. Bath and larder · Locked

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