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It started with soup. Two companions were eating carrots and cilantro. One liked his very hot. The other warm. Why the difference in preference? And is there an objective optimal temperature for eating soup? I decided to investigate.
In part the temperature at which food served and consumed is governed by safety and health. The guidelines stipulate that hot foods should be cooked to a core temperature of 75°C and held at 63°C or higher to avoid bacteria. But putting that aside, how does temperature affect flavor?
“Flavor is taste and smell,” says Dr. Arielle Johnson, author of Flavorama: a guide to discovering the art and science of flavor (harpercollins). “As for smell, heat makes flavor molecules more volatile. This increases the number of molecules in the air and therefore the aroma, which intensifies the flavor. For maximum impact, you should release the aromas as close to eating as possible. That is why lemon juice is added to the sauce at the end of cooking. Taste and smell reinforce each other, which is why lemon on a plate tastes brighter when it also smells like lemon.”
“As for taste,” he continues, “at low and high temperatures, our perception of taste weakens. Foods warm around body temperature have more flavor. One important exception is spiciness: the higher the temperature, the spicier something tastes.”
Taste sensitivity is also a factor: where are you on the scale from super tasters to hypotasters? “If you’re a big taster, you may prefer very hot or very cold foods,” Johnson says, since flavors at extreme temperatures are attenuated. “The sweet spot for a hippocater might be warm.”
Confectioners, aware of how cold temperatures dull flavor, increase the sugar in ice cream. Following the same principle, Johnson finds fermented fish overpowering at room temperature but delicious cold: “If there’s a strong food you’d like to enjoy more, eat it fresh,” he advises.
Part of the pleasure of piping hot ramen is how the flavor changes as it cools: rich in aroma when hot, blooming flavor when cool. Sipping it helps cool the broth and pushes the aroma molecules toward the nose to enhance the flavor.
Nigella Lawson extols the virtue of warm (carrying the “memory of heat”, as she puts it) in dishes like her nutmeg-scented custard tart. Nik Sharma recommends heating his cherry black pepper pie because the higher temperature intensifies its spicy flavor. For most Chinese cooks, piping hot remains the standard for everything from sweet and sour soup to dumplings.
High heat is also an obsession among an older generation that grew up without central heating and worries about food poisoning. The meat is ordered well done for this reason. Anything pink is practically a death wish. The obsession with eating on hot plates surely comes from the same place. It sounds like a slightly old-fashioned way of dining from a time when frying dishes was routine. As Johnson explains, hot dishes are only necessary for foods that cool quickly and become dull. “Don’t heat stew dishes too hot because it’s better to let them cool,” he says.
Texture also influences. “If the ramen cools even a little, the broth starts to freeze and become sticky in your mouth. You know too much fat,” says Tim Anderson, whose latest book Hokkaido (Quadrille) celebrates a region famous for its ramen. The opposite happens with ice cream. As the fat liquefies and becomes silky on the palate, you experience what food scientist Harold McGee calls “the birth of creaminess.” Special mention deserves the hot and cold combinations such as apple pie and ice cream, where each bite offers a variety of temperature, aroma and flavor.
A key learning from Tom Jackson’s book Fresh pasta: reinventing the pasta salad (Hardie Grant) is how temperature affects the qualities of pasta. The higher the temperature, the more easily it absorbs liquid or oil. Depending on its size and shape, this determines whether it is necessary to rinse the cooked pasta (to lower its temperature and remove excess starch) before dressing it.
However, personal taste often trumps good sense. I like cold pasta despite Jackson’s warnings against it. Cold pizza and cold bolognese offer comparable pleasures, including the umami sweetness of cold cooked tomatoes. There’s also an unabashed pleasure in eating at the refrigerator door, when it’s just you and the food and the instant gratification.
Of course, the temperature at which we eat food can also be a matter of habit and convenience. Anderson may be a ramen fan, but when he eats packaged ramen at home, he prefers warm ramen over blanched so he can inhale it faster. “I’m hungry and I’m in a hurry,” he says. There’s also a lot to be said for her ritual of pairing steaming tomato soup with a grilled cheese sandwich: “I dip the sandwich into the soup and when I’ve eaten most of it, the soup is cold enough. to sip,” he says. The second law of thermodynamics is used excellently.