Why passata is worth the late-summer effort

By late August, the greenhouse and the outdoor beds are usually groaning. There is only so much tomato salad, chutney and roasted tomato one household can manage. Passata is the answer. It takes a mountain of ripe fruit, turns it into something smooth and deeply savoury, and gives you a store cupboard ingredient that tastes of sunshine in February. On a smallholding, where gluts are normal and waste is a sin, a few hours of simmering and sieving pays you back all winter.

The method is simple, but the details matter. Ripe tomatoes, a heavy pan, a sieve or food mill, basil, salt, and clean jars. That is essentially it. What follows is the cottage-garden way: small batches, no special machinery, and a result that is far better than anything you can buy.

Choose ripe tomatoes and gather your kit

Any ripe tomato works, but the best passata comes from fleshy, low-water varieties. Plum types such as Roma, San Marzano and similar paste tomatoes give a thick, sweet pulp with fewer seeds. If you are using a mixture of cherry and beefsteak tomatoes, expect a looser passata and a longer reduction. Do not use underripe fruit; it lacks sugar and colour. A few blemishes are fine, but cut out any mould or hard green patches.

You do not need to peel tomatoes if you are passing them through a food mill or a fine sieve. The skins and seeds stay behind. If you only have a standard kitchen sieve, cook the tomatoes a little longer first, then push them through with the back of a ladle. For a very smooth passata, pass the pulp through a second time or line the sieve with muslin.

• A large, heavy-based saucepan or stockpot
• A food mill, fine sieve or muslin-lined colander
• A funnel, ladle and clean tea towels
• Sterilised glass jars or bottles with sound lids
• A deep pan with a rack for water-bath processing
• Basil, sea salt, and bottled lemon juice or citric acid if you plan to store jars on a shelf

Simmer, sieve and reduce

Rinse the tomatoes, remove the stalks and cut out any tough cores. Roughly chop larger fruit. Put them in the pan with a splash of water to stop them catching, then cook gently with the lid on for 20 to 30 minutes, stirring now and then. The tomatoes should collapse completely and release their juice. Do not boil hard at this stage; a gentle simmer preserves the sweetness.

Let the pulp cool a little, then pass it through your mill or sieve. Discard the skins and seeds. What you have now is passata, but it is usually thinner than you want. Return it to the cleaned pan and simmer uncovered, stirring often, until it coats the back of a wooden spoon. This can take 30 minutes to over an hour depending on the tomatoes and the width of your pan. Stir more frequently as it thickens, or it will spit and catch.

For a simple sauce rather than plain passata, soften a chopped onion and a couple of garlic cloves in olive oil before adding the sieved pulp. Simmer with a tied bunch of basil stalks, then remove the stalks before bottling. The result is richer and ready to spoon over pasta.

Basil, salt and the question of acidity

Season your passata with sea salt, starting with about a teaspoon per litre, then taste. Salt is for flavour, not preservation. Add fresh basil leaves in the last five minutes of simmering, or put a leaf or two into each jar before filling. The basil will perfume the sauce without turning bitter. If you prefer a cleaner tomato flavour, leave the basil out and add it when you open the jar.

Tomatoes sit on the border between high-acid and low-acid foods. For safe shelf storage, you must increase their acidity. Add one tablespoon of bottled lemon juice or a quarter teaspoon of citric acid per 500 ml jar before sealing. Do not rely on salt, oil or sugar to preserve them. If you would rather not add acid, freeze the passata instead and use it within a few months.

Bottling and processing for a shelf-stable store

Wash your jars or bottles in hot soapy water, rinse well, and sterilise them in a low oven or by boiling. Keep them hot until filling. Bring the passata back to a simmer, then ladle it into the hot jars through a funnel, leaving about 1.5 cm of headspace. Wipe the rims with a clean cloth dipped in vinegar, add the acid and basil if using, and seal with clean lids. Do not overtighten.

Process the jars in a deep pan of boiling water, covered by at least 2.5 cm of water, with a rack or folded tea towel underneath to stop them touching the base. Boil for 40 minutes for 500 ml jars and 50 minutes for 1 litre jars. Start timing once the water returns to a rolling boil. Lift the jars out carefully and leave them undisturbed for 12 to 24 hours. Check that the lids have sealed; if any have not, refrigerate and use within a week.

• Label with the date and variety so you can compare batches next year.
• Store in a cool, dark cupboard and use within 12 months for best flavour.
• Once opened, keep in the fridge and use within five days.
• If you are short on time, freeze the passata in sturdy bags or tubs instead of processing jars.

A taste of summer in winter

There is a particular pleasure in opening a jar of your own passata on a grey January evening. The colour is deep red, the smell is sweet and green, and the sauce needs nothing more than a little olive oil, a pinch of chilli and a bowl of pasta. For the smallholder or cottage gardener, it is the simplest way to stretch a tomato glut into something precious. Simmer, sieve, bottle, and put summer on the shelf.