WEBVTT - How Does Taste Work? 0:00:01.840 --> 0:00:07.600 Welcome to brain Stuff, a production of iHeartRadio, Hey brain Stuff, 0:00:07.680 --> 0:00:13.080 Lauren Vogelbam here. We learn about taste in grade school, 0:00:13.600 --> 0:00:16.200 and out of the five senses, it seems like one 0:00:16.280 --> 0:00:20.160 of the most simple. There are no cones, rods, or lenses. 0:00:20.440 --> 0:00:25.080 There are no timponic membranes or minuscule bones. Yet scientists 0:00:25.160 --> 0:00:28.880 know less about taste than they know about sight and hearing. 0:00:29.640 --> 0:00:34.479 So why is taste so mysterious? To start with? Taste 0:00:34.520 --> 0:00:37.720 is wrapped up in the greater issue of flavor. A 0:00:37.840 --> 0:00:41.200 taste is a chemical sense perceived by the specialized nerve 0:00:41.200 --> 0:00:44.640 receptors that make up our taste buds. Our perception of 0:00:44.680 --> 0:00:48.000 flavor is a fusion of multiple senses, not just taste, 0:00:48.120 --> 0:00:53.000 but also smell, touch, and temperature. In addition to taste buds, 0:00:53.040 --> 0:00:56.240 we have nerve cells throughout our oral and nasal cavities 0:00:56.240 --> 0:01:00.400 that detect molecules that give us a sense of heat, wellness, 0:01:00.480 --> 0:01:03.920 or dryness. For example, you know foods or drinks that 0:01:03.960 --> 0:01:08.280 are spicy, hot, minty, or puckery. It gets even more 0:01:08.319 --> 0:01:12.479 complicated because our interpretation of sensory data is always subjective, 0:01:12.800 --> 0:01:17.360 and flavors are perhaps more subjective than most Some people 0:01:17.400 --> 0:01:20.720 have inherited genetic traits that make certain foods that others 0:01:20.760 --> 0:01:26.080 find pleasant taste disgusting, like cilantro. Others have higher or 0:01:26.120 --> 0:01:29.920 lower concentrations of taste receptors than most of us, and 0:01:30.240 --> 0:01:33.480 as we all know, food tastes different to different people, 0:01:33.920 --> 0:01:37.800 we don't all enjoy the same flavors. Over the past 0:01:37.800 --> 0:01:42.000 couple decades, science has expanded its definition of taste. We 0:01:42.080 --> 0:01:47.920 now understand that we have at least five primary tastes sour, bitter, sweet, salty, 0:01:48.120 --> 0:01:53.320 and savory, with at least four more hypothesized. Science has 0:01:53.360 --> 0:01:57.120 also challenged the tongue map, that biology class staple that 0:01:57.440 --> 0:02:02.280 charts distinct regions of taste and is almost certainly bunk food. 0:02:02.320 --> 0:02:05.960 Scientists have even tampered with taste receptor cells, blocking or 0:02:06.000 --> 0:02:08.840 stimulating them in an effort to cut sugar and salt 0:02:08.840 --> 0:02:13.360 out of foods without sacrificing flavor. Today, let's talk about 0:02:13.360 --> 0:02:19.720 the physiology and psychology of taste and flavor. Taste begins 0:02:19.800 --> 0:02:24.079 with electrical impulses. Sure of food or drink is usually 0:02:24.080 --> 0:02:27.400 involved too, But as we've talked about before on the 0:02:27.400 --> 0:02:33.079 show Sensations, you know our bodily responses to stimuli like pressure, light, 0:02:33.320 --> 0:02:38.160 or chemical composition only become perceptions like touch, vision, or 0:02:38.200 --> 0:02:42.320 taste when they reach the brain. In our mouths and noses, 0:02:42.520 --> 0:02:46.800 certain chemical stimuli activate the chemo receptors responsible for our 0:02:46.840 --> 0:02:51.400 perceptions of taste and smell. Because both our reactions to 0:02:51.480 --> 0:02:54.280 the chemical makeup of an object. The two senses are 0:02:54.320 --> 0:02:57.840 closely related, though the chemo receptors involved with each tend 0:02:57.919 --> 0:03:02.880 to pick up on slightly different ranges of molecules. That's why, 0:03:02.960 --> 0:03:05.600 if you've ever been gunked up with a cold, the 0:03:05.639 --> 0:03:09.360 subtlety of food was probably muted. You weren't getting the 0:03:09.400 --> 0:03:14.000 full picture. In humans, the chema receptors that detect taste 0:03:14.120 --> 0:03:19.480 are called gustatory receptor cells. About fifty of these receptor cells, 0:03:19.600 --> 0:03:22.920 plus some basal and supporting cells, make up a single 0:03:23.080 --> 0:03:27.760 taste bud. The average adult has around ten thousand taste buds, 0:03:28.000 --> 0:03:30.920 and not just on your tongue. Some are spread elsewhere 0:03:30.960 --> 0:03:34.760 throughout your oral cavity. On your tongue, many of your 0:03:34.800 --> 0:03:38.240 taste buds are contained in what's called papilli. These are 0:03:38.320 --> 0:03:41.520 the small bumps that dot the tongue. There are three 0:03:41.560 --> 0:03:45.280 different types, arranging from smaller mushroom shaped bumps on the 0:03:45.320 --> 0:03:47.720 front of the tongue with only a few taste buds each, 0:03:48.080 --> 0:03:51.400 two larger, deep, goblet shaped bumps at the back of 0:03:51.440 --> 0:03:55.600 the tongue with hundreds of taste buds each. The papilli 0:03:55.680 --> 0:03:58.920 help you taste food and drink because they greatly increase 0:03:58.960 --> 0:04:01.840 the surface area of your tongue and therefore the number 0:04:01.840 --> 0:04:04.240 of taste buds that can fit on it. And they 0:04:04.240 --> 0:04:06.880 can help create friction between the tongue and food at 0:04:06.920 --> 0:04:10.600 breaking the food up. And they can help saliva wash 0:04:10.680 --> 0:04:13.880 over food and actually get particles of it to our 0:04:13.960 --> 0:04:17.800 taste buds. Each taste bud is a little bundle set 0:04:17.839 --> 0:04:20.120 into the surface of the tongue or the base of 0:04:20.120 --> 0:04:23.279 a papilla. A taste bud looks a little bit like 0:04:23.320 --> 0:04:26.039 a flower bud. Each of the petals that make it 0:04:26.120 --> 0:04:31.120 up is a gustatory receptor cell. These cells have spindily 0:04:31.200 --> 0:04:33.920 protrusions coming up to the tip of the taste bud 0:04:34.200 --> 0:04:39.560 called gustatory hairs. These taste hairs can brush up against 0:04:39.560 --> 0:04:41.320 bits of food that you eat with the help of 0:04:41.360 --> 0:04:45.320 your saliva. Proteins on the surface of the hairs will 0:04:45.360 --> 0:04:49.240 bind with particular types of molecules and stimulate the sensation 0:04:49.480 --> 0:04:53.520 of taste. The receptor cells are connected to nerve fibers 0:04:53.640 --> 0:04:57.279 that pass on electrical impulses to the gustatory area of 0:04:57.320 --> 0:05:02.640 the cerebral cortex. The brain then interprets the sensations as taste, 0:05:03.839 --> 0:05:07.680 together with other sensations like smell and maybe heat. If 0:05:07.680 --> 0:05:10.359 you just ate a chili pepper, your brain gives you 0:05:10.400 --> 0:05:14.920 a concept of flavor. There are a lot of compounds 0:05:14.920 --> 0:05:18.000 in foods and drinks that give them their nuanced flavors. 0:05:18.720 --> 0:05:23.240 For strawberries, researchers have isolated over three hundred compounds that 0:05:23.320 --> 0:05:27.400 affect our experience of smell and taste. For tomatoes, it's 0:05:27.520 --> 0:05:33.680 over four hundred. Until recently, scientists accepted four basic categories 0:05:33.720 --> 0:05:39.080 of tastes, sweet, salty, sour, and bitter. These categories are 0:05:39.120 --> 0:05:41.840 the building blocks of flavor and at the root of 0:05:42.000 --> 0:05:46.760 other tastes. Each primary taste triggers a particular taste receptor. 0:05:47.040 --> 0:05:51.440 The receptors can and do respond to multiple tastes. The 0:05:51.440 --> 0:05:56.640 four basic tastes went unchallenged for years. However, in the 0:05:56.680 --> 0:05:59.479 early nineteen hundreds, a Japanese chemist by the name of 0:05:59.520 --> 0:06:02.920 Kikune Keda set out to identify the compound in a 0:06:02.960 --> 0:06:06.760 common soup broth called kombu dashi that made it taste good. 0:06:07.960 --> 0:06:10.280 He was looking to find something that could be produced 0:06:10.440 --> 0:06:14.160 cheaply and easily that could add flavor to nutritious foods 0:06:14.320 --> 0:06:18.160 and thus entice people to eat better. He was also 0:06:18.240 --> 0:06:21.000 looking to make money, and wouldn't we all be lucky 0:06:21.040 --> 0:06:24.560 to make money doing something good for the world. In 0:06:24.640 --> 0:06:27.919 nineteen oh eight, he landed on the molecule glutamic acid 0:06:28.040 --> 0:06:31.320 as the key stuff in kambu or seek help that 0:06:31.440 --> 0:06:36.080 makes dashi so sippable. It's an amino acid, a building 0:06:36.080 --> 0:06:39.640 block of protein that we understand today occurs in lots 0:06:39.680 --> 0:06:43.400 of meats, cheeses, and vegetables, from steaks to parmesan to 0:06:43.520 --> 0:06:48.760 tomatoes and Kida. Further proposed that our detection of it 0:06:49.040 --> 0:06:52.480 is a fifth basic taste, a one that humans developed 0:06:52.480 --> 0:06:55.520 an affinity for because it occurs in these nutritious foods. 0:06:56.480 --> 0:07:00.280 In English would call this taste savory. But when Haita 0:07:00.440 --> 0:07:03.200 came up with a product that carries this taste, a 0:07:03.279 --> 0:07:07.160 salt format of glutamic acid called monosodium glutamate or MSG, 0:07:07.839 --> 0:07:11.880 he called the taste umami in his marketing materials, ubami 0:07:12.000 --> 0:07:16.640 being a colloquial term for tasty. Yes, the word umami 0:07:16.720 --> 0:07:21.360 is just an early nineteen hundred's marketing term. Kaida's research 0:07:21.480 --> 0:07:24.880 didn't really hit the Western world until the MSG company 0:07:24.920 --> 0:07:28.000 that he started began trying to expand outside of Asia 0:07:28.040 --> 0:07:32.040 in the nineteen eighties. By the way, MSG is fine 0:07:32.200 --> 0:07:35.120 for the vast majority of people to consume unless you're 0:07:35.120 --> 0:07:38.120 on a low salt diet. In general, if you feel 0:07:38.160 --> 0:07:40.400 a little weird after eating a dish that it's heavy in, 0:07:40.760 --> 0:07:46.440 you're probably just dehydrated that always drink water anyway. Researchers 0:07:46.600 --> 0:07:50.680 have since found the taste receptors responsible for sensing amino 0:07:50.760 --> 0:07:56.400 acids like glutamic acid, thus solidifying savory as a fifth taste. 0:07:57.680 --> 0:08:00.440 Now that the gate is open, however, other contend have 0:08:00.560 --> 0:08:05.200 entered the field. French researchers have identified a potential gustatory 0:08:05.240 --> 0:08:08.880 receptor for fat, so fatty might be a sixth taste. 0:08:10.040 --> 0:08:12.920 Other researchers have suggested that our basic tastes could further 0:08:12.960 --> 0:08:18.480 include metallic, watery and alkaline, the opposite of acidic. And 0:08:18.840 --> 0:08:22.080 just as scientists are re examining the basic tastes. They're 0:08:22.080 --> 0:08:26.840 also redefining the tongue map. The classic tongue map divided 0:08:26.840 --> 0:08:30.480 the tongue into regions of sensation bitter in the back, 0:08:30.760 --> 0:08:33.720 sour on the sides, salty on the front edge, and 0:08:33.800 --> 0:08:37.440 sweet at the tip. This concept also goes back to 0:08:37.440 --> 0:08:39.920 the early nineteen hundreds. A lot of work was being 0:08:39.920 --> 0:08:43.480 done in nutritional science at the time, but since then 0:08:43.880 --> 0:08:46.840 a research has determined that although the tongue does have 0:08:47.000 --> 0:08:51.480 varying degrees of sensitivity, some areas can perceive certain tastes 0:08:51.520 --> 0:08:54.680 better than others. There was no real truth to the 0:08:54.840 --> 0:09:00.600 strict tongue map. Furthermore, although taste receptors often react strongly 0:09:00.640 --> 0:09:05.200 to a single taste, most do respond to multiple taste stimulations. 0:09:06.160 --> 0:09:10.280 The primary tastes gave early humans clues about what food 0:09:10.440 --> 0:09:14.800 was good to eat and what was potentially harmful. Sweet 0:09:14.800 --> 0:09:19.720 foods had energy loaded carbohydrates. Salty foods had important vitamins 0:09:19.720 --> 0:09:24.000 and minerals. Savory foods had protein. Sour foods could be 0:09:24.040 --> 0:09:28.800 healthy like apples, or spoiled like rotten milk. Bitter things 0:09:28.800 --> 0:09:33.000 could be poisonous. And actually one bit of the tongue 0:09:33.000 --> 0:09:35.600 map was more accurate than the rest. The back of 0:09:35.640 --> 0:09:40.280 the tongue is particularly sensitive to better flavors. The raining 0:09:40.360 --> 0:09:43.760 hypothesis goes that this was useful and last ditch detection 0:09:44.000 --> 0:09:48.560 of toxic substances before we swallowed them. These days, the 0:09:48.640 --> 0:09:52.800 processed foods we eat are often painstakingly flavored by professional 0:09:52.960 --> 0:09:56.840 flavor chemists, so the tastes that we experience when we 0:09:56.880 --> 0:10:00.600 eat them are sometimes signifying nutritional value, but it isn't 0:10:00.640 --> 0:10:05.240 actually there, but we still crave and respond to our 0:10:05.400 --> 0:10:10.000 ancestral favorites. Of course, a person's taste is a lot 0:10:10.040 --> 0:10:14.800 more complicated than that. Physically, we perceive other flavors beyond 0:10:14.920 --> 0:10:19.920 the five ish primary tastes. Spicy foods can feel hot 0:10:20.120 --> 0:10:23.720 due to two different categories of compounds that both trigger 0:10:23.840 --> 0:10:26.320 the same nerve receptors in your mouth and knows that 0:10:26.400 --> 0:10:31.079 sense actual heat. They're chemically tricking your mouth into thinking 0:10:31.080 --> 0:10:35.600 that it's slightly on fire. Chili peppers and the capsaisin 0:10:35.679 --> 0:10:38.960 in them affect one type of nerve receptor. A plant 0:10:39.040 --> 0:10:42.959 in the mustard family, including masabi and other pungent things 0:10:43.000 --> 0:10:46.720 like cloves, garlic, cinnamon, and ginger, will activate a second 0:10:46.760 --> 0:10:50.320 type of heat receptor. This is also the receptor that 0:10:50.440 --> 0:10:55.839 registers the slight nasal burn of carbonation and sodas. Black 0:10:55.840 --> 0:10:59.719 pepper hits both of those Sesshuan peppercorn or any of 0:10:59.760 --> 0:11:03.360 the numbing hot dishes it's made with that activates both, 0:11:03.640 --> 0:11:06.360 plus yet another type of receptor, the same one that 0:11:06.400 --> 0:11:11.520 your body uses to sense what's basically tickles extremely light touches, 0:11:11.679 --> 0:11:14.920 like when a bug lands on you. It produces the 0:11:14.960 --> 0:11:17.640 same feeling as the pins and needles you get when 0:11:17.679 --> 0:11:20.280 a limb falls asleep, or when you hit your elbow 0:11:20.440 --> 0:11:25.600 just wrong, or feel a vibration, and so yes, tickle 0:11:25.880 --> 0:11:31.239 is a flavor. Evolutionarily, these plants probably developed these compounds 0:11:31.280 --> 0:11:35.120 to be unpleasant to mammals like us, and therefore to 0:11:35.280 --> 0:11:38.640 prevent us from eating that plant's fruit and thus crushing 0:11:38.720 --> 0:11:40.840 up its seeds before they have a chance to sprout 0:11:40.880 --> 0:11:45.560 and grow. But suckers, some of us humans decided that 0:11:45.600 --> 0:11:49.679 we enjoy those flavors or bitter tasting things like black 0:11:49.720 --> 0:11:54.640 coffee or artichokes. That's part of why, despite having figured 0:11:54.640 --> 0:11:57.080 out a lot about our taste buds and other flavor 0:11:57.120 --> 0:12:00.160 chema receptors, we still don't have a very good idea 0:12:00.240 --> 0:12:04.000 of how any given person's overall sense of taste works. 0:12:05.320 --> 0:12:08.880 Your brain doesn't just catalog the molecular makeup of a peanut, 0:12:08.920 --> 0:12:13.360 butter and jelly sandwich. It processes the smooth and soft 0:12:13.400 --> 0:12:17.640 and maybe crunchy textures and the cravable combination of salty, 0:12:17.760 --> 0:12:21.839 savory and sweet sensations, and maybe throws in a little 0:12:21.880 --> 0:12:24.800 nostalgia for a time that someone you love made a 0:12:24.840 --> 0:12:29.040 similar sandwich for you. The same sandwich eaten on two 0:12:29.120 --> 0:12:32.880 different days might even taste different, just based on your mood, 0:12:34.120 --> 0:12:38.679 like sometimes when you're upset, eating anything feels gross, and 0:12:38.880 --> 0:12:43.760 research has shown that hunger really can affect flavor. In 0:12:43.800 --> 0:12:46.520 a study from back in two thousand and four, groups 0:12:46.520 --> 0:12:49.640 of students who had not eaten in sixteen hours could 0:12:49.720 --> 0:12:53.720 perceive weaker sucrose and salt solutions than those who had 0:12:53.760 --> 0:12:58.200 eaten only an hour before. In order to perceive a taste, 0:12:58.280 --> 0:13:01.160 the students who had just eaten needed a sucros concentration 0:13:01.559 --> 0:13:05.559 fifty percent higher, and assault concentration doubled that of those 0:13:05.600 --> 0:13:09.640 who had not eaten. But apparently our poison detecting sense 0:13:09.720 --> 0:13:12.960 never rests. An empty stomach or full stomach had no 0:13:13.040 --> 0:13:18.200 effect on the perception of bitterness, speaking of it's time 0:13:18.200 --> 0:13:20.319 for me to go get a refill on my coffee, 0:13:20.800 --> 0:13:22.760 which I take with just a little bit of oatmelk. 0:13:23.360 --> 0:13:30.920 It's a matter of taste. Today's episode is based on 0:13:30.960 --> 0:13:33.760 the article how taste works on how stuffworks dot com, 0:13:33.800 --> 0:13:37.000 written by Sarah Dowdy. Brain Stuff is production of iHeartRadio 0:13:37.080 --> 0:13:39.520 in partnership with how stuffworks dot Com and is produced 0:13:39.520 --> 0:13:42.760 by Tyler Klain. Four more podcasts for my heart Radio, 0:13:43.120 --> 0:13:46.559 visit the iHeartRadio app, Apple Podcasts, or wherever you listen 0:13:46.600 --> 0:13:58.360 to your favorite shows.