What should I do if an opened jar looks or smells wrong?

A bulging lid, a broken seal, a jar that spurts or fizzes when opened, cloudiness, mould, or any off smell means you dispose of it without tasting it. Not a fingertip, not a corner. This is the one preserving rule with no recovery attached.

In season, with Gusto · No. 07 · August

The August tomato glut: sauce, can, freeze

Q: Do I really have to add lemon juice to canned tomatoes?

Yes. Tomatoes sit right on the borderline of the acidity that keeps a sealed jar safe, and modern varieties vary. Every current home-canning authority directs you to acidify every jar of tomatoes regardless of variety or method. It is a small quantity and it is the difference between a preserved food and a gamble.

Q: Is it safe to seal jars by turning them upside down?

No. Sealing and processing are different things, and a seal formed by residual heat is not evidence that the contents reached a safe temperature throughout. Inversion sealing, oven canning and dishwasher canning have all been out of the guidance for decades.

Three exits from the same crate. You choose by how many hours you have, not by how ambitious you feel at nine in the evening.

Season: August
Routes: 3
Fastest: 20 min
Read: 8 min

Choose by the clock in front of you

Every August the same crate appears. From a garden that over-delivered, from a neighbour who has given up, from a market stall at four in the afternoon selling the last of the day for almost nothing. It is a magnificent thing to be handed, and by Thursday a third of it will be liquid at the bottom of the box if nobody makes a decision.

The mistake is treating this as a project. People look at a crate of tomatoes, imagine a shelf of gleaming jars, run out of evening at the halfway point, and lose the lot. The correct approach is triage: sort the crate by condition, then pick your route by the hours actually available to you tonight — not the hours you would like to have.

The tomatoes at the bottom are not waiting for the weekend. Nothing in that crate is waiting for the weekend.

Sort first, and sort ruthlessly. Anything with a soft patch, a split, or a bruise goes into the cook-tonight pile — heat does not care about appearance and those will not survive storage in any form. Anything firm and unblemished can go to the freezer or to jars. Anything already showing mould goes in the bin, and I mean the whole tomato, not the good half; mould in soft fruit runs deeper than the visible spot.

— Gusto · The kitchen · August, windows open

How much time do you have?

40 minutes — sauce tonight. Eat some, refrigerate the rest for up to about four days. No equipment beyond a pan. The default answer, and there is no shame in it being the only one you ever use.
20 minutes — freeze. Whole, raw, in bags. The fastest route by a wide margin, the most forgiving, and the one nobody writes about because it is not photogenic. Keeps for months.
Half a day — can. Shelf-stable for a year or more, and the only route with rules you cannot improvise around. Worth doing properly or not at all.

Route one · sauce — forty minutes, one pan, and the soft ones

This is where the damaged tomatoes go and it is the route that rewards a glut most immediately. Core the tomatoes, cut out any bad patches, and cut them roughly — skins on, seeds in. Both of those will be dealt with later and neither is worth the labour of removing now.

Into a wide pan with a generous pour of olive oil, a good pinch of salt, and nothing else. Not garlic yet. Not basil yet. Over medium heat, uncovered, and then you leave them alone for twenty-five to thirty-five minutes, stirring occasionally, while a startling amount of water leaves the pan as steam. The wide pan is the whole trick: surface area is what lets the water go, and a tall narrow pot will simply boil the tomatoes in their own juice for an hour and give you something thin and dull.

You will know it is ready when the sauce mounds slightly behind the spoon rather than running back to fill the gap, and when the colour has shifted from bright red toward brick. Now, off the heat, pass it through a food mill if you have one — which removes skin and seed in a single motion and gives you a texture you cannot get any other way. If you do not have one, a stick blender will do, and the skins will simply become part of the body of the sauce. Only now do the garlic, the basil, and the final oil go in, off the heat or over a very low flame, so their aromatics survive.

Eat a third of it tonight. The rest keeps in the refrigerator for around four days, or goes into the freezer, which is route two by another name.

Route two · freeze — twenty minutes, no skill, no equipment, no rules

Nobody writes about this route because a photograph of a freezer bag has never sold a magazine. It is, nonetheless, what I would tell most people to do with most of a large crate, and it is the answer for anybody who arrives at this in the wrong mood at half past nine at night.

Wash the tomatoes. Dry them properly. Cut out the core. Put them in freezer bags whole and raw, flatten the bags so they stack, press out the air, and freeze. That is the entire method. There is no blanching, no peeling, no acidifying, no processing, and no way to get it wrong.

The pleasure of it comes months later. Run a frozen tomato under a warm tap for a few seconds and the skin splits and slides off in one piece — far more easily than blanching ever achieved, because the ice crystals have already ruptured the cells beneath the skin. That cell rupture is also why a thawed tomato is soft and weeping and useless in a salad, and completely fine in every cooked application. Do not plan on slicing them. Plan on sauces, braises, soups, and stews.

They will keep well for six months or more. Label the bags with the month, because you will not remember, and a freezer is where good intentions go to become archaeology.

Route three · can — half a day, real rules, and a shelf that lasts a year

Canning is the only route in this piece with a safety mechanism you must respect rather than a technique you can improvise around. I am going to be very clear about what those rules are and equally clear about where the numbers come from, because the numbers are not mine to invent.

Boiling-water canning of tomatoes is a genuinely accessible thing to do at home — the equipment is a tall pot with a rack, jars with new lids, a jar lifter, and a funnel. Before you start, get the whole set in one go rather than discovering at the wrong moment that you have no way to lift a boiling jar out of a boiling pot; a water-bath canning kit covers the lifter, funnel, rack, and bubble tool together. The lifter in particular is not a luxury. Improvising it with tongs is how people end up with a broken jar in a full pot of boiling water and a burnt forearm.

That is an affiliate link. If you buy through it, HowTo: Food Edition earns a small commission and your price does not change. Nothing about the safety guidance below depends on which kit you own.

The acid rule, which is not optional. Tomatoes sit right at the boundary of the acidity that makes a sealed jar safe, and the varieties in your crate may sit on the wrong side of it. Every jar of home-canned tomatoes must be acidified, whatever the variety and whatever the recipe. The standard direction is two tablespoons of bottled lemon juice or half a teaspoon of citric acid per quart jar, and half those quantities — one tablespoon of bottled lemon juice or a quarter teaspoon of citric acid — per pint. Bottled, not fresh, because fresh lemons vary and the guidance was written around a standardised product.

The addition rule. Do not add garlic, onions, peppers, celery, mushrooms, or oil to tomatoes destined for a boiling-water canner. Every one of those is a low-acid ingredient and adding them makes the jar a low-acid product, which requires a tested pressure-canning process instead. Can the tomatoes plain. Build the sauce on the evening you open the jar.

The processing rule. I am not printing a processing time, and I would be suspicious of any writer who did without asking where you live. The correct time depends on the product, the jar size, whether you pack hot or raw, and your altitude. Take the current tested time for your exact combination from a home food preservation authority — the National Center for Home Food Preservation, or your national or regional extension service — and follow it to the minute.

Read this before you fill a single jar

Clostridium botulinum forms spores that survive boiling. In a sealed jar there is no oxygen, and in a low-acid environment those spores can germinate and produce a toxin that you cannot see, smell, or taste. Acidity below roughly pH 4.6 prevents that growth, which is the entire reason the lemon juice is not a flavouring and not a suggestion.

This also means: no inversion sealing, no oven canning, no dishwasher canning, and no adjusting a processing time because the jars looked done. A seal is not proof of a safe process. If a jar bulges, leaks, fizzes, smells wrong, or looks cloudy when you open it months later, dispose of it without tasting it.

For current tested recipes and processing times, use a home food preservation authority such as the National Center for Home Food Preservation or your regional extension service. Nothing on this page replaces a tested recipe.

The questions I am always asked in August

Do I really have to add lemon juice to canned tomatoes?

Yes, and it is the one instruction in this piece that is not negotiable. Tomatoes sit right on the borderline of the acidity that keeps a sealed jar safe, and modern varieties vary. Every current home-canning authority directs you to acidify every jar of tomatoes regardless of the variety or the method. It is a small quantity, it does not make the tomatoes taste of lemon once cooked, and it is the difference between a preserved food and a gamble.

Can I use fresh lemons instead of bottled juice?

No. Fresh lemons vary considerably in acidity from fruit to fruit and season to season, and the guidance is written around bottled juice precisely because it is standardised. Bottled lemon juice or powdered citric acid. This is one of the very few occasions on which I will tell you to reach for the bottled thing.

Can I add garlic, onion, peppers, or olive oil before canning?

Not in a boiling-water canner. Those are all low-acid ingredients and adding them turns your acidified tomatoes back into a low-acid product, which needs a tested pressure-canning process instead. Make the sauce plain, and add the garlic and the oil in the pan on the night you open the jar — which, incidentally, is when they taste better anyway.

How long do I process the jars for?

That depends on the product, the jar size, whether the tomatoes are packed raw or hot, and your altitude, which is why I am deliberately not printing a number here. Look up the current tested time for your exact situation from a home food preservation authority such as the National Center for Home Food Preservation or your national or regional extension service, and follow it exactly. A processing time is not a guideline you adjust to taste.

My grandmother turned the jars upside down and they sealed fine.

They sealed. Sealing and processing are different things, and a seal formed by residual heat is not evidence that the contents reached a safe temperature throughout. Inversion sealing, oven canning, and dishwasher canning have all been out of the guidance for decades. Your grandmother was lucky, and I say that with genuine affection for her.

What if I open a jar and something looks wrong?

A bulging lid, a broken seal, a jar that spurts or fizzes when opened, cloudiness, mould, or any off smell — do not taste it to check. Not a fingertip, not a corner. Dispose of it without tasting. This is the only preserving rule with no recovery attached to it, which is why it is the last thing I will say to you about jars.

Colophon

Written by Gusto in August, with a crate on the floor and a decision to make · safety guidance follows current home food preservation authorities, not my own preferences.

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