“There’s just something missing.” Many of us have said this while cooking. If you’ve ever searched for an elusive ingredient to lend depth and flavor to a dish, there’s a good chance that missing ingredient was acid. Like salt and pepper, but much more often overlooked, some form of acid is usually necessary to season food well. Acidity is one of the five main taste sensations we will ever have the pleasure to experience, so it makes sense to carefully consider it in our cooking.
In Ruhlman’s Twenty, chef Michael Ruhlman’s book about cooking technique, he says it’s difficult to describe exactly what acid imparts to food, but it’s something like “brightness.” Whereas seasoning with salt helps make a food taste more like itself, seasoning with acid can amplify the flavors in a dish, add depth and help bring everything into balance.
Acid to the Rescue
We have many choices when it comes to adding acid to a dish. The list that follows is by no means comprehensive. All we are trying to do here is kickstart our cooking brains into thinking a little bit more about sourness as an important element in our cooking palette. Keep in mind that just as we don’t necessarily want to taste salt itself in our food, we usually don’t want to notice the acidic ingredient by itself either. Be cautious of that heavy hand.
Citrus: The easiest way to lend a sour note to any food is to squeeze a wedge of citrus over the finished dish. Lemons, limes, oranges and grapefruit are known to be useful in taming the fishiness in many seafood dishes, but they also make a number of other foods sing. Just for starters, try citrus juices on grilled chicken and cooked vegetables; blended into homemade vinaigrette dressings; and stirred into mayonnaise and condiments.
Vinegar: Vinegar is a fundamental ingredient in many cooked sauces, but like citrus, it can also be used as a finishing flavor. Stir a dash of white wine vinegar into your next cream-based soup, or a dash of red wine vinegar into a vegetable purée, such as butternut squash soup. You might be surprised at the range of foods that are improved this way. Try it for yourself and soon you will likely find, as Pliny the Elder did in the first century, that “no other sauce serves so well to season food or to heighten a flavor.”
The quality of vinegar is more important than the type, Ruhlman says, so it’s better to spend money on an excellent bottle instead of on several fancy-flavored bottles. His favorite all-purpose seasoning vinegar is sherry vinegar, though he says red wine vinegar, white wine vinegar and cider vinegars are all useful. Hot sauce usually has a hefty dose of vinegar in it—a good choice if you want some heat with your acid.
Fermented dairy products: Buttermilk, crème fraîche, goat cheese, kefir, sour cream and yogurt are all useful acidic ingredients. Try them stirred into mashed root vegetables or cooked grains. A dollop of goat cheese can be lovely on top of a grilled steak or pork chop. Make an easy sauce of crème fraîche or sour cream blended with garlic and fresh herbs.
Fermented and pickled fruits and vegetables: Think outside the dill pickle jar. In Australia, it’s common to add slices of pickled beets to hamburgers, and they add a counterpoint of tangy flavor just as well as dill pickle slices. Sauerkraut goes well with most meats—not just sausages. Kimchi is tasty fluffed into brown rice or added to eggs. There is more variety in the world of fermented foods than you might ever have imagined, and their acidity makes other foods taste better. Learn about it in Sandor Katz’s dense but infinitely useful book, The Art of Fermentation.
Wine: Wine is another important acid in cooking, but rather than being added at the end of cooking, it usually needs to be cooked when included in a recipe. After browning meats and vegetables in a sauté pan, add a little bit of wine to deglaze the pan, scraping up all the sticky bits left in the pan, and let at least half of the wine simmer off. Use this as a sauce to dress whatever you had cooked in the same pan. To make the sauce a little more complex, swirl in some butter or cream at the end. You can also include wine in fantastic homemade soup stocks (red wine in beef stock; white wine in vegetable, chicken or seafood stock). As with vinegar, quality matters. Use wines for cooking that you enjoy drinking by themselves.
Acidic produce: All fruits and vegetables contain acid, though of course some are more potent than others. A few chopped tomatoes might be all your pot of beans needs to end up sufficiently brightened. A sweet-and-sour sauce made from cranberries obviously goes well with roasted turkey, and tangy pickled capers are famously good with smoked salmon. Also try stuffing roasted green tomatoes into your enchilada and taco mixtures, or adding some especially sour greens such as sorrel or mustard greens to a tossed salad. To take full advantage of the flavor potential of any produce, try to use it as close to harvest as possible. In On Food and Cooking, food scientist Harold McGee explains that just after harvest, plant cells quickly use up available acids and sugars. “This is why vegetables picked just before cooking are more full-flavored,” he says.
Coffee: Although it may be surprising on this list, coffee is indeed acidic. You can use freshly ground coffee in rubs for meats that will be roasted or grilled, or as an addition to sauces and stews, especially chili. Add a little bit of brewed coffee to dessert frostings to give them a more complex flavor. In all of these cases, it’s unlikely the eater will detect a coffee flavor. Instead they’ll just notice a little special something—that elusive missing ingredient that makes food memorable.