When cooks read “season to taste,” they reach for the salt shaker. That’s not a bad start: A judicious sprinkling with salt will awaken many a dull dish. But just as a little salt unlocks flavor, so can a few drops of acidity.
Add a shot of vinegar to a stew of white beans and shrimp and notice how the earthy flavor of the beans gains definition and complexity.
Do the same with pureed winter squash and a dish dominated by rich and sweet now has a round, full-fruit character.
Though the results may be similar, salt and acidity work differently. Salt is a flavor potentiator — it works chemically to make other flavors taste like themselves. Acidity as a seasoning gives a dish backbone or structure, which allows other flavors to stand out.
It doesn’t take much. As with salt, you don’t want to taste the seasoning itself; you just want the effect it has on other flavors.
Sometimes only a couple of drops of lemon juice will be all that it takes.
Many cooks understand this. After all, what would a salad taste like dressed only with oil? It’s the vinegar that makes vinaigrette.
And think of the way a squirt of lemon elevates the flavor of broiled or grilled fish.
How many times have you deglazed a roasting pan with red wine? It’s not just the fruit flavor you’re after but the acidity, too. Cooking down tomatoes in a sauce or soup has the same effect.
If you’ve heard about a “gastrique” served with a dish, it’s basically a syrup of boiled vinegar and sugar. Traditionally, it is used to season dishes of meat combined with fruit. Used clumsily, it’s a fancy version of sweet-and-sour sauce.
I wouldn’t think of cooking vegetables without acidity — a squirt of lemon for sauteed broccoli, a hit of red wine vinegar for summertime ratatouille. And almost every time I cook fruit, there’s bound to be a jolt of citrus to balance the sweetness.
But all acids are not created alike. Any well-stocked pantry should have several to choose from.
Start with citrus fruit: Lemons are the most common and the most useful because they are harvested so early that they don’t have much flavor besides their tartness. Meyer lemons, which are harvested fully ripe, are an exception. Oranges have a sweeter sourness than lemons, and limes are tart but have a bracing herbaceous quality.
Then there is vinegar or, more appropriately, vinegars. Every pantry ought to have several. It’s funny how cooks who brag about $30-a-bottle extra-virgin olive oil will make do with cheap vinegar.
Good vinegars offer more variety and typically can be found for less than $15 a bottle.
The mainstay acid should be a good- quality red-wine vinegar, one that tastes like an extremely tart but otherwise well- made red wine.
Good white-wine vinegars are harder to make at home because they oxidize quickly. But the standard restaurant supply model made by Vilux is perfectly acceptable. Or use champagne vinegar, which is sharp with a subtle sweetness. Rice vinegar is also sweet, but with a rounder texture.
Balsamic vinegar is known for its sweetness, but in a burnt-sugar-caramel way that doesn’t fit most culinary purposes (and certainly not salads). It is useful in marinades, though, or brushed on a piece of meat before grilling. Sherry vinegar has a distinctive nutty, winelike quality and great depth of flavor.
Finally, don’t overlook that old American standby, apple cider vinegar. Good ones have terrific fruit character. Look for unfiltered or unpasteurized.
Acidity also works in surprising ways. Adding a little sour can smooth out bitter flavors. The other night, I made a soup from greens I’d harvested from my garden. Because dandelions predominated in the mix, the soup had a bitterness. Adding a little sherry vinegar rounded out the flavors, adding a quality that was almost sweet.
Be careful when adding acidity because acids are not just flavors, they’re chemicals.
The most obvious negative effect of acidity is that it discolors green vegetables, turning them olive drab (it changes the chemical structure of the chlorophyll pigment).
Acidity will also affect the texture of protein, “cooking” it without heat. If left to marinate too long, it will break down the structure and create a mealy texture.
Along the same lines, if a sauce is too acidic it will curdle cream. Also, acids will delay the softening of dried beans if added too early in the cooking process.
At the same time, there are occasions when acids are used for their chemical properties, with no flavor effect at all. The most notable is using sour ingredients in pastries, such as pie crusts, cakes or even pancakes. You usually don’t add enough to change the flavor, just enough to weaken the flour’s gluten, creating a more tender texture.
Would you have guessed that a little squeeze of something sour could accomplish so much?
