We’ve all been there… peering into our refrigerator on a hungover Sunday morning, only to happily realize there is still a slice or two of pizza left from the late-night binge feast a few hours earlier. In that moment of desperation, any sustenance is welcome, but that cold pizza definitely doesn’t taste the same as it did the night before. The ingredients are all the same – pepperoni, cheese, jalapeños and olives – but something seems to be missing. It doesn’t seem to make any sense.
Why does the temperature make that much of a difference when it comes to the flavor of food?
Short Answer: Human beings evolved to prefer hot food to cold, as it was an evolutionary advantage that saved time for more important things, allowed us to derive more energy and nutrients, and protected us from illness. Chemically speaking, our taste perception increases with warm foods, as opposed to cold ones, based on boosted activity of the microscopic channels in our taste buds.
From Cold Eaters to Hot Foodies
A few million years ago, before human beings discovered fire, the only available food was cold, just like every other animal on the planet. Eating our food raw was the only option, but around 2 million years ago, Homo erectus made the miraculous discovery of fire and everything in our evolutionary trajectory changed. Suddenly, early hominid species were able to build fires to cook their food, ward off predators, ensure that they got full nights of sleep, and drove the early development of our impressive brains.
This was one of the first major efforts by humankind to outsource certain biological responsibilities – namely chewing and digesting cold food – which freed up a huge amount of time. Essentially, it takes a lot more work for the body to digest cold food, since it relies solely on saliva and gastric juices to occur. Hot food is basically pre-digested, due to the exothermic reaction of fire.
The production of heat, and its application to food, causes chemical reactions and changes to the food, changing the basic nature of meats, grains and vegetables to make them much easier to digest. Think of a cow, with its multiple stomachs, where regurgitated food must pass back into the mouth to be further chewed in order to be full digested. Heating up our food allowed us to spend our energy, both mental and physical, in the pursuit of greater things. In fact, our bodies can’t even handle a diet of purely raw meat anymore; we don’t have strong enough stomach acids, an evolutionary fact that has occurred at some point over the past 2 million years.
By heating food, we increase the caloric availability of our food, from which we derive our energy. Studies have shown that humans are able to get roughly 30% more energy from cooked wheats and grains and 90% more from cooked legumes and starches because our digestive tracts can immediately begin sucking out calories and nutrients from that cooked food.
Aside from being easier to digest, cooking food can eliminate far more food-borne illnesses, and is more pleasant to our senses. When you heat up food, the molecules become more volatile, flying off the food in the form of aromas, which keep us coming back for more. Our senses of smell, therefore, has evolved to encourage us to eat foods that are healthier for us, particularly those that smell and taste better when they are cooked, such as meats, vegetables, beans, etc.
However, that doesn’t full explain the sense of taste, specifically why cooked foods tend to taste better than cold foods.
Our Talented Tongues
A great deal of research has gone into taste and smell, because food manufacturers want to understand everything they can about what flavors and tastes appeal to consumers. They also want to determine ways to mask unpleasant flavors, and that all comes down to the taste receptors in our tongue.
As it turns out, the tiny channels in our taste buds, which send electrical signals to the brain related to taste, tend to function at a higher level when temperatures are higher. Foods and fluids have more powerful astringent, umami, sour and sweet flavors in our mouth when they are warm, which can work both ways – for flavors that are both good and bad. The main exception to this is bitterness, which appears to be more powerful when something is cold.
For example, people prefer their coffee hot because the beverage’s bitter flavor can be better masked when the coffee is warmed up. On the other hand, when considering something like ice cream, the sweet taste is only activated when the ice cream begins to melt in our mouth, not when we simply lick the top of an ice-cold carton of mint chocolate chip. Those tiny receptor channels in our tongue, which pass along messages about flavor, do not function as well when the substance is cold.
There are more than 10,000 taste buds, on average, on the human tongue, and each bud consists of between 50 and 100 cells, all of which can detect every type of taste – salty, sour, sweet, bitter and umami. Some foods are preferred cold, such as soda, while others are preferred hot, such as tea and cocoa. Clearly, hot food doesn’t necessarily mean that it is better, it just means that a certain flavor profile will be more intense. Obviously, cranberry juice, which already has quite a bit of an astringent flavor, wouldn’t be nearly as pleasant when it is warmed up and that flavor profile is increased even further.
Understanding more about this delicate balance, and the process of taste perception, helps food scientists develop new methods to mimic flavors and potentially improve the health of our dietary intake.
Over the course of evolutionary history, our taste buds have mainly developed to prefer warmer foods, in the search for more powerful and rewarding flavors. So, while that slice of cold pizza may be just what the doctor ordered on that hungover Sunday morning, the salty and savory flavors on that slice would be even more satisfying if you popped it in the oven first and gave your taste buds a real treat!