Raw, Cooked and Canned Tomatoes Are Three Different Ingredients

A February tomato is pale, firm, faintly sweet and smells of almost nothing. A can of tomatoes sitting on the shelf beside it was picked in August, ripe, and processed within hours.

Which is why the apparent snobbery runs the other way from how people expect. In a cooked dish, the can is very often the better ingredient, and insisting on fresh is the mistake. The reverse is also true: a good August tomato eaten raw is a thing no can will ever approach. They are different ingredients and the error is treating them as grades of the same one.

What ripeness actually builds, and what cold destroys

A tomato develops its aroma compounds late, on the plant, in the last days of ripening. There are dozens of them and they are volatile, which is the whole reason a ripe tomato smells like something across a room.

Two things remove them. Picking early, which is what a tomato that has to survive a truck requires — it will soften and redden off the vine but it will not build the aroma it never had time to make. And cold: below about 55°F the enzymes that produce those compounds shut down, and after a few days they do not restart. A refrigerated tomato is permanently blander, and letting it come back to room temperature does not bring the smell back.

So: whole tomatoes on the counter, never the refrigerator. A cut one goes in the cold because at that point spoilage outranks aroma, and it should be used the next day.

Canned tomatoes are a cooked product and that is the point

Canning heats the tomatoes, which destroys most of those delicate raw aromatics and concentrates the things that survive heat: acidity, sweetness, and glutamate.

That glutamate is the reason canned tomatoes punch above their weight in savory cooking. Tomatoes are naturally high in it, and heat concentrates it further, which is why a tomato base tastes meaty in a way the arithmetic of its ingredients does not explain, and why tomato with parmesan or with anchovy is so much louder than either alone.

It also means a can is already partway through the cooking. A sauce from a can needs less time than a sauce from fresh, because the breakdown has begun.

The formats are not interchangeable

Whole peeled is the most useful and the most honest, because you can see what you are getting. Crush them by hand and you control the texture, and the ones that are hard or pale are visible rather than hidden.

Crushed is whole tomatoes plus purée, which means part of the can is already cooked down and it will thicken faster. Convenient; slightly less control.

Diced usually contains calcium chloride to keep the cubes from falling apart, which works exactly as advertised and is occasionally the wrong thing: the calcium firms the pectin, the same way acid firms it in a bean, so diced tomatoes stay in pieces no matter how long you simmer them. Good for a chili you want chunky, bad for a smooth sauce.

Purée and passata are smooth and already strained. Fast, and missing the texture that makes a sauce interesting.

Paste is a different thing entirely: tomatoes reduced to a fraction of their volume, which makes it the most concentrated savory ingredient in an ordinary cupboard. Fried in oil until it darkens and smells nutty, it is one of the fastest ways to put a floor under a dish, and frying it rather than stirring it in is most of the difference.

Cooking tomatoes takes longer than people give them

A tomato sauce simmered for fifteen minutes tastes sharp and raw and faintly tinny. The same sauce at forty-five minutes tastes round and sweet, and nothing was added.

Several things are happening over that time. Water is leaving, which concentrates everything. The harsh volatile acids are driving off while the less volatile ones stay, which shifts the balance from sharp to savory. And the sugars and amino acids are slowly browning, which is where the depth comes from.

The instinct when a sauce tastes sharp is to add sugar. Sometimes that is right, and more often the answer is twenty more minutes, because the sharpness is a timing symptom rather than a sweetness deficit. A pinch of baking soda neutralizes some acid if you are genuinely out of time, at the cost of some brightness.

And a tomato sauce takes salt late, because it reduces. Salted at the start, a sauce that loses a third of its volume arrives too salty with nothing to do about it.

The skins and seeds question

Skins are tough and they roll up into unpleasant little tubes in a long-cooked sauce. For anything smooth, peel — blanch thirty seconds and the skin slips, which is one of the five jobs blanching does.

Seeds and the gel around them are where a large share of the glutamate and the acidity live. The habit of seeding tomatoes for a sauce throws away flavor to avoid a little extra liquid, and the liquid can simply be cooked off. Seed them for a salsa or a salad where water on the plate matters. Keep them for anything cooked.

Roasting is the best thing to do with a mediocre fresh tomato

A disappointing tomato has the sugar and the acid and not much aroma. Roasting concentrates what is there and manufactures new flavor through browning, which is a genuine rescue rather than a consolation.

Halved, cut side up, a little oil and salt, 325°F for an hour or more. They collapse, darken at the edges, and taste more like a tomato than they did raw.

This is also the answer to the August problem of everything ripening at once. Roasted tomatoes keep a week in the refrigerator under oil and freeze well, and they are a better use of a glut than a sauce nobody got around to canning.

Which tomato for what, briefly

Raw, as itself: in season, from somewhere near you, at room temperature, with salt and oil and nothing else. Salt it ten minutes ahead so it draws out some juice and seasons through.

A quick sauce: good canned whole peeled, crushed by hand, forty minutes.

A long braise or a soup: canned, plus a spoonful of paste fried in the oil first.

A chunky chili or a stew: canned diced, where the calcium chloride is doing you a favor.

Anything out of season where the tomato has to taste of something: the can, every time, and cherry tomatoes as the one fresh exception, since they ripen more reliably and lose less on the journey.

The general rule is the one worth keeping. Out of season, the can beats the fruit, and there is no loyalty owed to the fresh one just because it is fresh.

Part of Recipes & Technique.