Molly asks via Twitter:
I’d like to start this answer by stating that, yes, I completely know it’s a rhetorical question. However. Just because it’s not expecting an answer, doesn’t mean it doesn’t deserve to be answered. It’s one of the more obscure pleasures in life, answering rhetorical questions. At least, it is for me.
Despite what we may have learned in elementary school, the whole taste apparatus is enormously complicated. We have the tongue, which is, by and large, pretty simple. As near as I can tell, its main goal is to ensure that what we are about to eat is not going to kill us. We know it does four or five things really well: sweet, salty, bitter, sour, and possibly umami. Oh, and spicy. That’s six things. And mustardy-hot. Seven. Seven things.
Most of the things in the above list are either important to keep us alive: sugar is a really good source of energy, salt is one of the fundamental mechanisms keeping the body alive, and sour is a good indication of vitamin C, which keeps the scurvy at bay. Bitter things are often poisonous, so it’s nice to catch those early. And umami… there’s some controversy as to whether umami is as fundamental as the other four. Probably it’s a good indication of protein, but I need to sit down with some good umami research before I’m fully clear on the whats and the whys.
As for the two hot sensations, those aren’t our fault. That’s the fault of the plants that produce them. They produce chemicals that try to keep us from eating them. However, as I’ve said before, we are a strange and contrarian race, and we will happily go out of our way for pain if we’re pretty sure that it either won’t kill us or, if it will kill us, it will have been worth it. So while originally it was evolutionarily prudent for those plants to make themselves inedible, nowadays it’s really useful for them to be enjoyed by us, as we’ll plant and cultivate them forever as long as they set our mouths ablaze. Who knows, perhaps that was the plan all along.
Where it starts to get complicated is that most of what we consider to be “flavor” bypasses the tongue entirely. Volatile Organic Compounds (VOCs), which is Science Speak for “things we can smell”, float into our nasal cavities and attach to miscellaneous chemical receptors, which cause all of the scents and flavors which aren’t on the list above to be interpreted.
Thus far, we have two systems at work: one which requires the food or drink to physically touch the tongue, and the other that is much happier if the food is far away from it, just taking what floats on the air. Now consider that, as we are exposed to certain tastes and smells, our senses become overwhelmed. The receptors for those flavors run out of energy to tell us about them, which is why air freshener manufacturers are going through such efforts to alternate smells and the like, so that you can keep smelling the freshener over time. It’s also why people can hold jobs in a Yankee Candle store for any amount of time without either killing themselves or stuffing their noses full of spray-foam. So, by and large, it’s a useful apparatus, but it does complicate the tasting mechanisms.
And, although this doesn’t really indicate our complete exploration of the mechanisms of taste and smell, I will add but one more mechanism: heat. Cold things don’t go through the air very well, and they slow down chemical reactions, such as the ones that tell your central nervous system that you are testing something. Hot things both make chemical reactions go faster, and they allow more Volatile Organic Compounds (smelly things) to float up into your sinus cavities.
Test the Science
Test my theory by mixing up a few drinks and grabbing a straw (this test is best done with friends, of course, and some great hors d’oeuvres). Or, break out the blender and try the milkshake test (below).
|Frozen Hot Chocolate||Frozen Affogato Shake with Espresso Granita||Honeydew-Cucumber Shake with Cucumber Granita|
With all of that, let’s think straws vs. no straws. If you were drinking, say, a milkshake without a straw, then you get a big clump all at once. There’s not a lot of room in your mouth, and so not much air circulation. Also, the milkshake is pretty cold, so you won’t get much going on by way of nerve impulses or VOCs.
If you drank the same milkshake with a straw, then you would just get a little at a time. That small amount of milkshake hits your tongue, which heats the relatively small amount of milkshake rather than being instantly frozen by it. The warmed milkshake lets off VOCs, and also your tongue can maintain its tasty chemical reactions. That, combined with all the air that’s flowing through your system as part of the mechanism of sucking liquid through a straw, you have a lot more flavor happening.
And that, in a nutshell, is why some things taste better through a straw.