Science behind taste, flavours: How we perceive food, develop palate

So, what’s in a taste? You tell us, because personal definitions are palates apart. Taste, as we are going to learn, is more than just the sweet, salty, bitter, sour that we’ve been told our tongues perceive.Taste is a combination of how a food smells, looks, feels, and sounds. It has to do with nurture and nature as well. Krish Ashok has been so fascinated by the science of taste and flavour that he wrote a whole book on it -- Masala Lab, the science of Indian cooking. He calls it a science nerd's exploration of Indian cooking.Sweet, salt, bitter, sour… we’ve been told since eighth-grade biology class that different parts of the tongue detect different tastes. The tip of the tongue detects sweetness for instance, the back bitterness.Ashok, an expert on the science behind flavours, says taste-bud specialisation is more well-distributed than we’ve been taught, meaning each part of the tongue specialising in one taste can sense other tastes as well.The tip of the tongue, which we thought was dedicated to tasting only sweet, can also taste bitterness. It’s perhaps how the bitter aftertaste came to be.“We have five kinds of taste buds in our tongue,” Ashok says. “The first one is sweetness, which detects all kinds of sugars. This is important because it's the brain's way of detecting oh, here's some high-calorie food. So if you eat this, I want you to eat lots of it. We are all addicted to sweetness as a result of these taste buds. The second is saltiness. Saltiness is important because our body requires a certain amount of sodium in order for it to function. It is required for the heart, it is also required for sort of neurotransmission of messages between neurons and so on. So saltiness is absolutely essential, so we detect a certain level of saltiness in our food. “Sourness comes from our ability to detect acids,” he says. “This is the presence of hydrogen and hydronium ions, If you will. And then you have the detection of bitterness, which essentially comes from having to detect poisons. So a lot of the bitter detection taste buds tend to be at the back of your tongue. This is so that before you swallow food you end up detecting if there are any poisons. Poisons tend to be bitter alkaloids. A class of chemicals that are the most common kinds of poisons that plants produce tend to be bitter, so bitterness evolved as a mechanism to detect poisons. “Just so we're clear,” he adds, “not everything that is bitter is bad for you, but most poisons tend to be bitter. And the last one and the most recently discovered is umami. Umami is a set of taste buds on your tongue that detect a very specific amino acid. Amino acids are building blocks of proteins and umami taste buds detect something called glutamic acid. The taste sensation of umami is sort of meaty and savory. And it is often associated with the consumption of meat, red meat particularly, and also shellfish like shrimp, prawns, crabs and so on. It is also a critical component of MSG or monosodium glutamate, which is simply the sodium salt of glutamic acid.” Not just nose: Importance of smellA flavour is clearly a complex blend of sensory data. It is believed that our sense of smell is responsible for 80 per cent of what we taste. When our noses are blocked, food tends to taste bland. Our sense of smell also gets stronger the hungrier we are.Ashok, in his exploration of the science of flavor, looked at two types of smell -- orthonasal olfaction and retronasal olfaction and the impact they have on flavor and taste. Orthonasal olfaction is what your nose detects from sniffing: a rose, an orange, roast chicken and so on. Retronasal olfaction is the perception of odours that emanate from the oral cavity during eating and drinking, and contributes largely to the sense of taste.“The perception of flavor is a very multidimensional experience,” Ashok says. “In fact, taste as you detect with your taste buds on the tongue is no more than 20 per cent of the overall element of flavor perception. The large bulk of flavor perception happens in the nose. Beyond smell and taste, we also have a mouth field so we have the trigeminal nervous system in the mouth that is able to detect various things such as the sensation of heat, the sensation of low or high pH, various kinds of viscosities, and so on. “We're able to detect different kinds of textures in food,” Ashok says. “It's all of these signals in addition to in fact the sound of, say, a crunching potato chip, the sight of a brown and grilled piece of chicken as you're about to eat it. All these signals go to the brain and the part of the brain that deals with it is the same part of the brain that deals with memory and nostalgia. This is why all food experiences are deeply personal and completely non objective.” What happens when you eat“When you start chewing food the saliva starts breaking down some of the complex molecules, and particularly when fats start getting broken down the spice aromas and the volatile molecules that are dissolved, the fats get released and they travel to the back of your mouth and then upwards through your vintube back into your nasal cavity when you smell them,” Ashok says. “In fact, the experience of the aroma of food before you eat it is a very tiny component of the larger experience of aroma as part of the flavor of something. In fact, many things smell funny before you eat it, but taste delicious after you eat it. Cheese is an example. Grilled eggplant is another example. Even fish is an example. ”Let’s go below the surface a bit to the sub-threshold of tastes. The science behind how tastes work in tandem to amplify each other. Basically, the scientific reason for why your grandma always added a pinch of salt to kheer. Or why jaggery is preferred when making Indian sweets, because of its slightly salty taste. Yes, there is a scientific explanation to it…“Each of our senses of taste are also connected with each other,” Ashok says. “For instance, a very tiny amount of sugar. In fact, sugar that is even below our perceptible threshold for sweetness can actually improve savory dishes. This is why a seasoned chef will add a tiny pinch of sugar even when making curries and gravies. Likewise, a seasoned chef will also use a tiny amount of salt when making desserts. Because the tiniest presence of salt, even though it does not taste perceptively salty, has the effect of enhancing sweetness and every other flavor for that matter. So you do have these kinds of combinations. Sweetness also arrests bitterness, for example sourness can sometimes amplify bitterness in some situations.“Temperature too impacts how we perceive taste. That’s why some foods are best hot, others cold, and some at room temperature.“Our sense of taste is also very temperature-dependent,” Ashok says. “The lower the temperature, the less effective our taste buds are at detecting tastes. This is why coffee that is cooled down to room temperature is often very bitter, whereas coffee that's really hot does not taste as bitter because at very high temperatures our taste buds don't work well either. Likewise, ice cream that is just out of the freezer seems to taste just right, but the moment it melts the ice cream becomes cloyingly and unbearably sweet. Because at that temperature our taste buds actually work better. ”Cooking secrets: How to hack your palateOkay, so now let’s get to cooking. Just how much salt and sugar are ideal for a dish?“Different societies and different cultures have different levels of tolerance for salt and sugar, so there is no way to identify a specific amount of salt and sugar in a dish,” Ashok says. “For instance, Indians generally tend to like food far saltier than Americans or Europeans do. We also are able to tolerate a higher degree of sweetness in our deserts as well. But you can generally assume that anywhere between 1 per cent to 2 per cent by weight of the dish is roughly the right range for salt. You may want to adjust on the lower side or the higher side depending on the person's tastes. The other interesting thing about salt is that we often use iodised salt. This was part of a 1960s and ’70s mechanism to reduce hypothyroidism and goiter in society. It was an easy way to get people to not have iodine deficiencies. But today, as long as your diet includes iodine from many other sources, you can be choosy about what kind of salt you use. So I would recommend using iodised salt when you're making gravies, but when you're deep-frying food sodium iodide has a tendency to burn and cause sort of bitter taste, so if you're deep frying something like a pakoda I would urge you to avoid the use of iodised salt. ”We’ve got the science of sweet and salt, but hey, we are the land of spice, and no podcast on flavour is going to be complete without understanding the science behind spice. “The chili plant is remarkable in that its way of defending against animals from eating it is by producing an interesting molecule called capsaicin that is able to fool our trigeminal nervous system sensors into thinking that you have actually consumed something that is high temperature, meaning hot,” Ashok explains. “That's why we use the word hot for the sensation of chilies because it is literally fooling your brain into thinking you have consumed something really, really hot. It fits into the sensor that detects high temperature and it therefore sends the brain into panic mode, which then sends a lot of sweat. A lot more blood circulation into the place, into your mouth, into your face, and so on. You start sweating all in an attempt to bring your temperature down, except that this is all a phantom sensation. Pretty soon the brain realises, oh, this is really a fake sensation. And over time it will adjust and increase your capacity and tolerance for capsaicin, so people who eat food with a lot of chilis can generally continue to consume food with even more chilies, right? So the brain also generates a small amount of endorphins because it assumes you might be in pain and the brain’s way of dealing with pain is to give you a little bit of pleasure so as to balance out that pain. This is why people who like hot and spicy food are addicted to hot and spicy food, because that little bit of phantom pain actually gives you real pleasure.”Audio production: Prateek Kapoor