Leftovers — like whatever's in that green jar near the back of the third shelf — can be a dreaded fridge-horror specter past their prime as soon as they hit the Tupperware. But oh, those beautiful exceptions! Beef bourguignon, lamb stew, posole, chili — there are lots of soups, stews and slow-cooked braises that really do taste better after they've had a cooling stay in the fridge followed by reheating and second-day service.
Why is that? "How good leftovers taste has a lot to do with the structure of the food matrix and its flavors," explains Kantha Shelke, an Institute of Food Technologists spokeswoman, food chemist and rheologist who, among other things, specializes in the aging of ingredients: "Food matrices that don't change much over one or two days — such as soups and stews — will generally taste just as good or even better with storage."
That's especially true if a dish has lots of spices and strong-flavored elements such as garlic, onion, ginger or lemon grass — plus some fat. Day One, those strong-flavored components tend to stick out a bit too much. But Day Two, they mellow and meld, making the dish they're served in rounder and more pleasantly flavored.
Combined with meats, aromatics like garlic and onion also help slow spoilage and the occurrence of what flavor chemists call "WOFs" — those dreaded "warmed over flavors" that happen when meats oxidize.
Fats and collagens are also key to sustained good flavor. That's why lamb, beef and pork, which have plenty of both, do much better the second time around than chicken breasts or fish.
How a dish is cooked, cooled and reheated also affects how it will taste during encore performances. Take braised lamb shanks. They're seared first, combined with sauteed vegetables and then slow-cooked with stock in the even heat of an oven.
"If you were to just heat that hunk of meat in a slow cooker, it might come out tender but you wouldn't have the Maillard reactions that happen between sugars and amino acids to produce the darker, more flavorful and aromatic compounds we crave in a slow-cooked dish," Shelke explains. You also wouldn't have caramelization that adds even more color and aroma — all important for the second- and third-time-around flavors.
When cooled, starches, fats and fibers in a dish reabsorb flavor compounds, trapping them until the dish is reheated. Because those compounds are so volatile, rapid cooling with the lid on is the best way to keep more of them from flitting off into the atmosphere. And when reheating, prolonged high heat is a flavor-zapping no-no. Instead, reheat to a boil, then simmer until internal food temperatures reach a safe 165 degrees.
When reheating, you can also add things in. Chicago chef Bill Kim of BellyQ, UrbanBelly and Belly Shack, says his favorite home leftover dish is his mother-in-law Lola's sancocho, a flavorful Puerto Rican soup of mixed meats with tomatoes, root vegetables, squash and plantains that Kim enlivens with Korean accents. The flavors deepen over time, making the soup base well-rounded. "But everybody always picks out the parts they like best, like the meats, when you first serve the soup," Kim says, "so after a day, I usually just cook more meat to add in."
He garnishes each bowl with a drizzle of Korean hot sauce, some fresh cilantro, avocado slices and fried plantain chips. "Garnishing is really important to add brightness and fresh flavor contrast to soups or stews that have mellowed out over time," he says. "You want that mellow roundness, but adding the right accents is what really makes it sing."
Leftovers and food safety
You want to get the most bang out of your food buck by making good use of leftovers, but cooling and reheating brings some food-safety risk. To stay safe, follow these simple storage and heating rules:
Immediately refrigerate cooked foods that have not been consumed within 2 hours of preparation
Divide cooked foods into smaller containers to allow for rapid cooling and also to facilitate rapid reheating of smaller portions
Use a thermometer to ensure leftovers have been heated to a safe temperature, above 165 degrees in the center
Bring sauces, soups and gravies to a boil before re-serving
Never reheat leftovers in crock pots, slow cookers or chafing dishes
Source: Institute of Food Technologists
Prep: 45 minutes
Cook: 2 hours, 20 minutes
Makes: 8 quarts, about 12 servings