Too hot? Too cold? Or just right: Swetha Sivakumar takes on serving temperatures

Why did we evolve to like piping-hot food, and what secrets is ice-cream hiding? Temperature tells us food is safe, and cold can hide a cupful of sugar.

When dal boils, its temperature is close to 100 degrees Celsius. The temperature in the human mouth is about 37 degrees Celsius. While the dal has cooled a bit by the time it is served, the gulf in temperatures is still a large one. Most hot meals, in fact, tend to be served at temperatures of about 60 degrees Celsius.

(Adobe Stock)

Why do we like food this hot? And how does the body cope?

Well, there are some hacks we employ without even knowing it.

Pay attention the next time you take a bite of something that is still steaming, and note how you involuntarily suck in a vortex of air first. This is a reflex that helps cool food before it touches the palate or tongue.

A second hack is perspiration. As hot food causes temperatures to rise in parts of the body, perspiration kicks in to cool us down. This is often accompanied by a runny nose and watery eyes, in a phenomenon known as gustatory sweating.

This is something I fondly recall my dad experiencing often. Even in the sweltering Chennai summer, he loved his hot rasam-rice for lunch. Sweating profusely, and frequently wiping his face with a towel he brought to lunch for that very purpose, he would relish each meal fresh off the stove.

Cold dulls the tastebuds, which is why ice-cream, when melted, tastes so sugary. (Shutterstock)

Rather than navigate such spikes in temperature, why did we not simply evolve to prefer our food cooled? Well, most of our hot meals starts to lose a little something as they cool. That something is aroma.

Aroma molecules are tiny, airborne particles that drift off a dish and into the nose and mouth, where they are detected by olfactory receptors. The hotter the dish, the more aroma molecules are diffused — because heat gives the particles themselves more energy for movement, plus the particles’ primary vehicle is steam.

Aromas play a key role in our experience of flavour. Which means a hot meal that has cooled is, as my father always argued, simply not the same dish.

There is a second reason we evolved to prefer hot meals: heat is an indicator that food is safe. Bacteria flourish in temperatures of 4 to 60 degrees Celsius. Heat an item to more than 60 degrees Celsius and bacteria start to die. (This is also why most items at a buffet are kept either hot or cold.)

Finally, there is the factor of mouthfeel. Food often doesn’t “feel right” when it’s gone cold, and that’s because its textures have started to change. Most starches start to noticeably retrograde below 55 degrees Celsius. As they eject their water content and bond more closely, rice gets gluggy, potatoes turn into a lump, and chapatis and naans get stiff and dry. Even dal, which contains a fair amount of starch, starts to congeal. Fats, meanwhile, start to solidify. Melted cheese begins to cake; meats may turn rubbery.

There are, of course, foods that taste fine at room temperature, such as sandwiches, wraps and chaat. But these rely heavily on textures and crunch, without which they would “taste” more like mush and be less enjoyable.

Now a slight tangent, and a handy tip for those with a sweet tooth. Cold dulls the tastebuds, and so our perception of sweetness is lowered when we eat dessert. For this reason, kheer served hot needs a lot less sugar than ice-cream. And ice-cream, when melted, tastes so very sugary.

So, if you’re looking for healthier dessert options, start with a temperature check. Opt for warm over cold.

Bon appetit.

(To reach Swetha Sivakumar with questions or feedback, email upgrademyfood@gmail.com)