How to Make Passata and Bottle Tomatoes

Turn a summer glut into shelves of smooth tomato passata, the safe way, with the one rule that matters most: tomatoes always need added acid.

When the tomatoes come in all at once, bottling is the oldest answer in the book. A morning at the stove turns crates of soft, ripe fruit into rows of jars you can pull down in the middle of winter for pasta, soup and braises that taste like January. Passata, the smooth sieved puree that Italian families make by the dozen-litre, is the easiest place to start because it freezes the flavour of peak-season tomatoes with almost nothing added.

There is one piece of food safety you must get right, and it is not optional. Tomatoes sit on the borderline between high-acid and low-acid foods. Some modern varieties, and very ripe fruit, can drift into the low-acid range where the bacteria that cause botulism can survive a boiling-water process. The fix is simple and reliable: add a measured amount of acid to every jar. Do that, follow a tested process time, and bottled tomatoes are one of the safest things you can put up at home. Skip it and you should freeze them instead.

Passata Yield Calculator

Work out roughly how much passata your tomatoes will make, how many jars of your chosen size that fills, and the exact acid dose each jar needs. Enter the weight of fresh, ripe tomatoes you have to hand.

Equipment you will need

You do not need a fancy setup, but a few things make the day go smoothly and safely.

• A big stockpot for cooking the tomatoes down.
• A food mill (mouli) or a fine sieve. This is what separates passata from chunky sauce. A mill is far faster if you do this every year. A stick blender plus a sieve also works.
• Clean jars with new, undamaged lids. Preserving jars with fresh rubber rings, or jars with new two-piece or lug lids. Reuse jars, never reuse soft sealing rings or once-popped lids.
• A water-bath canner or a preserving unit. Any deep pot with a rack on the bottom and a lid works as a boiling-water canner, as long as the jars sit on the rack and can be covered by at least a few centimetres of water. A purpose-made preserving unit (the Fowlers Vacola style is the classic Australian one) does the same job with a thermostat and a fitted rack.
• Jar lifter or tongs, a funnel, a ladle and a clean cloth. Bottled lemon juice or citric acid, and salt.

The passata method, step by step

1. Wash and sort. Use ripe, sound fruit. Discard anything mouldy, bruised badly or showing soft rot. Wash well under running water.
2. Core and roughly chop. Cut out the hard stem core and quarter the tomatoes. Peeling is optional because the mill removes skins later, but blanching for peeling first (30 to 60 seconds in boiling water, then into iced water so the skins slip off) gives a slightly cleaner colour and flavour if you have time.
3. Cook them down. Tip the tomatoes into the stockpot and bring to a brisk simmer, stirring, until they collapse and soften, around 15 to 20 minutes. Heating them fast helps keep the colour bright and reduces watery separation later.
4. Mill or sieve. Pass the hot, soft tomatoes through the food mill or push them through a fine sieve. The skins and seeds stay behind and you are left with smooth passata. Return it to the pot.
5. Season and reduce (optional). Bring the passata back to a simmer. If you like it thicker, let it reduce until it coats a spoon. Keep it hot, near a simmer, right up until you fill the jars.
6. Acidify and salt the jars. Into each clean, hot jar put the measured acid (see the box above) and, if you like, up to 1 teaspoon of salt per 500 ml for flavour.
7. Fill, leaving headspace. Ladle the hot passata into the jars through a funnel, leaving about 1.5 cm (roughly 1/2 inch) of headspace at the top. Slide a clean utensil down the side to release trapped air bubbles, then wipe the rims spotlessly clean.
8. Lid and process. Fit fresh rings or lids. Process in a boiling-water canner or preserving unit (see the next section), following a current tested time for your jar size and method. Lift the jars out and let them cool undisturbed.
9. Check the seals. After 12 to 24 hours, press the centre of each lid. A sealed lid is firm and does not flex. Label, date and store.

Water-bath vs a preserving unit

Both methods do the same thing: they hold the filled jars at the temperature of boiling water for long enough to make them shelf-stable. Acidified tomatoes are safe with this style of processing. Low-acid foods like plain beans or plain tomato that has not been acidified are not, and need a pressure canner instead.

Whichever you use, the rule is the same: follow a current, tested recipe for the exact processing time. Times change with jar size, altitude and method, so use the chart from your preserving-unit manufacturer or a reputable, up-to-date preserving book rather than guessing. The table below shows how the variables fit together, not invented times.

Storage and shelf life

Once the jars have sealed and cooled, wipe them down, label them with the contents and date, and store them somewhere cool, dark and dry. A cupboard away from the stove and out of sunlight is ideal because heat and light dull the colour and flavour over time.

• Best quality lasts about 12 months. Sealed, acidified passata stays safe well beyond that if the seal holds, but colour and flavour are at their best in the first year, so eat last season's before this season's.
• After opening, refrigerate and use within a few days, just like a shop-bought jar. Tip what you do not use into a covered container and keep it cold.
• Check before you use. A sealed lid, clear liquid and a fresh smell mean it is good. A bulging or unsealed lid, spurting liquid, fizzing, an off smell or any mould means throw the whole jar out.

When to bottle: season and region

In Australia the tomato glut lands in the warm months, roughly January to April depending on your region, with the southern states peaking later than the tropics. That is the window to buy a box cheap at the market or pick your own beds clean in one go. Bottling a glut in autumn means homegrown passata right through the cold months when fresh tomatoes are expensive and flavourless. The how to grow tomatoes guide covers getting that glut in the first place.

Troubleshooting

Watery layer or separation

A thin, watery layer settling under thicker pulp is normal and safe. It happens when enzymes break down pectin before the tomatoes are fully cooked. Reduce it by working quickly and heating the tomatoes fast at the start, or by cooking the passata down further before bottling. Just shake the jar before use.

Jars did not seal

If a lid has not sealed within 24 hours, do not store it on the shelf. Refrigerate that jar and use it within a few days, or reprocess it with a fresh lid within 24 hours. Common causes are a rim that was not wiped clean, a reused or damaged lid or ring, too little headspace, or jars cooled in a draught.

A sealed jar later unseals

A jar that pops its seal weeks later has usually spoiled, often from a nick on the rim or a poor seal that slowly failed. Discard the contents. Do not taste it.

Floating fruit or siphoning

Passata is smooth so floating is rarely an issue, but if you bottled whole or crushed tomatoes, fruit floating to the top is cosmetic. Siphoning, where liquid is forced out during processing and lowers the level in the jar, comes from a too-fast temperature change or overfilled jars. Let the canner cool a few minutes before lifting jars, and keep to the right headspace.

Mould

Any mould means discard the entire jar. Do not scrape it off, do not taste the contents, and do not feed it to animals. Mould on a preserve is a sign the seal failed and the contents are no longer safe.

Frequently asked questions