Senses Month: A Taste of Science

The Naked Scientists get their teeth into the science of taste.
17 April 2018
Presented by Chris Smith, Georgia Mills
Production by Izzie Clarke.




This month we’re exploring the science of our senses. So far we’ve heard how our ears work, looked the visual system in the eye, and this week, we’re getting our teeth into the science of taste. Plus news of a discovery that could re-write the story of human origins, how some antibiotics can also block viruses, and how ants keep infections at bay in their colonies.

In this episode

Hand outstretched

00:54 - Giving human origins the finger

The human history behind a newly discovered middle finger bone.

Giving human origins the finger
with Huw Groucutt, University of Oxford

The story of how - and when - the first anatomically modern humans migrated out of Africa and spread around world has been challenged by a new fossil discovery from Saudi Arabia. A bone from a middle finger, together with hundreds of stone tools, have been uncovered and dated to a time much earlier than scientists had believed that our ancestors first left the African continent. Georgia Mills spoke with study author Huw Groucutt from the University of Oxford.

Huw - The textbook view of human origins at the moment suggest that our species - homosapiens - evolved in Africa and that all non-Africans are descended from a migration out of Africa about 50 or 60 thousand years ago, probably following the coastline out of Africa. We know that about 100 thousand years ago there was a very short-lived localised expansion to the Levant, and this is mostly known from a few sites in, what is today, Northern Israel. But the idea is this is just sort of a flash in the pan, it’s very localised and really that’s irrelevant to the major story of how Eurasians came to be.

Georgia - What have your found then that challenges this notion?

Huw - We’ve been working in Saudi Arabia that’s part of a big project for almost 10 years now and, until very recently we knew almost nothing about the area. We found, over the last few years, lots of archaeological sites and lots of animal fossils, but we were always missing human fossils. We found a site called Alwosta, and there we found a human finger bone; it’s the middle bone of the middle finger and it’s dated to 90 thousand years ago. So, even though it’s only one fossil, it’s enough to identify the species. It’s our species, homosapiens, so it’s showing that we were in that area 90 thousand years ago.

Georgia - Right. So you’ve placed at least one human at a place where we didn’t previously believed there would have been humans at this time?

Huw - Yes, that’s right. It was a very different sort of environment to where we knew people were living. We knew they were in the forests on the sort of doorstep of Africa in the Levant, and now we know they were deep in the interior of Arabia. Although it’s only one fossil, we found hundreds of stone tools so we know there were quite a few people living at this site, and there were many other sites like it in the area.

Georgia - How did you date it, and how are you sure it’s human? I’m guessing if it’s just a finger bone it’s not a particularly obvious fossil, if that makes sense?

Huw - We got very lucky really. In this region there are two sorts of possibilities: us or neanderthals. It fortunately turns out that this bone is quite different in us and neanderthals. Our middle finger bone is more narrow and elongated, whereas a neanderthal bone is shorter and squatter. But, to really be sure, we did CT scanning to get a 3D model, and then we compared this using a technique called geometric morphometrics to the same bone from various humans, various extinct hominins, and even things like monkeys and chimpanzees, and this very clearly showed that the fossil aligned with homosapiens; it’s a very similar shape. If I hold it to my finger it’s exactly the same shape and size.

With the dating, we used a method called uranium series dating. When a bone is buried in the ground it absorbs uranium and, over time, this uranium decays into thorium, and we can measure the precise ratio of these two isotopes to determine the age; it decays in a predictable rate. This gave us a date of 88 thousand years ago and to confirm that date we used other techniques to date the sediments of the site and animal bones at the site as well. And all of these techniques agreed with each other that the fossil was about 90 thousand years, which was great because often different techniques are applied and the don’t agree with each other, so it gets complicated. So this is a very well dated fossil in a very well dated site.

Georgia - What does this tell us then; what can we now infer about human history?

Huw - I think the major change is that the sort of textbook views suggesting we left Africa about 50 or 60 thousand years ago was based on the idea that we couldn’t leave Africa until there’d been some kind hi-tech sort of revolution - a human revolution and there are different forms of this. But, for example, some people argue that we needed bows and arrows or complex symbolic material culture to survive in Eurasia, which seems sort of odd but that was a common view. What we found is that we were spreading much earlier, using very simple kinds of material culture.

So our migration wasn’t based on some kind technological breakthrough, it was based much more on patterns of climate change. We know, periodically, North East Africa and Arabia witnessed very extreme climate change. Basically, monsoonal rains moved far inland and this transformed the area so there were lakes, and rivers, and grasslands, and abundant animals, and it was this transformed landscape that early humans could follow. So it changes the narrative from a kind of human revolution to one based much more on the environment and climate.



06:45 - Some antibiotics can help fight viruses

A new study has shown that an antibiotic kills bacteria AND prevents viruses from growing.

Some antibiotics can help fight viruses
with Akiko Iwasaki, Yale School of Medicine

“Common colds need common sense, NOT antibiotics,” or so the saying goes; this is because colds are caused by viruses, which don’t respond to antibiotics,  Or so we thought! Now a new study has shown that some classes of antibiotic agent - as well as killing bacteria - can put our cells into an antiviral state, preventing viruses from growing. And if we can work out how, this might help us to develop new forms of antiviral drug. Izzie Clarke spoke to Akiko Iwasaki from Yale School of Medicine who made the discovery...

Akiko - We often use antibiotics to treat bacterial infections that don’t resolve so, for instance, a doctor might prescribe antibiotics for a bacterial infection in the throat or something that is a festering wound in the skin, and a variety of other things. And it was known that antibiotics are very specific to bacteria and they’re really designed to kill specific bacterial groups. However, our finding shows that certain types of antibiotics, known as the aminoglycosides, can trigger antiviral responses in mice, and we’ve tested the effect of antibiotics in a variety of viruses including herpes simplex virus, which is a causative agent for genital herpes. We tested this against influenza virus infection, which is the cause of flu, and Zika virus which can be transmitted through sexual contact as well. In all cases, an application of neomycin prior to viral infection protected the mice against these viruses.

Izzie - That’s amazing! So basically, you’ve applied a type of antibiotic which is, in its name, more liked to tackling bacteria but you’ve seen this antiviral response in a wide range of viruses. So how exactly does this work and how did you come across this?

Akiko - We took the antibiotics, the neomycin, and put it onto the skin of the mice just as you would do with neosporin that you would buy from pharmacies where you would apply the cream onto the skin. We took a similar approach where we apply the neomycin onto the vaginal cavity or, in some cases, we applied it through the nose for infections like influenza virus so it wasn’t swallowed by the mice. As soon as the neomycin was applied to the skin, what happens is that the host cells, which in this case is the skin cells, take up antibiotics and induce signals to allow leukocytes, which are these white blood cells that are circulating in the blood, to come into that area. These leukocytes then take up the antibiotics in the skin and start producing factors known as type 1 interferons. These interferons can then bind to neighbouring cells to promote protections against viral infections.

Izzie - Would we see this response in just any type of antibiotic?

Akiko - No, that’s not correct. We actually tested several antibiotics and found that only one of them had this antiviral effect. We really don’t want to promote overuse and misuse of antibiotics because that can give rise to bacteria that are resistant to antibiotics, and that’s a huge problem in the medical field.

Izzie - Yeah, absolutely! Obviously this is true in mice; what about humans? How strong is this effect of neomycin?

Akiko - Yes. We would love to know what happens in humans. We haven’t applied neomycin in human skin to see what happens, but we’ve added the antibiotics on human cells in tissue culture and show similar kinds of interferon production from human cells suggesting perhaps similar kinds of effects can be seen in humans.

Izzie - Wow! So why is this important and what does it mean for the future?

Akiko - In the future, what we’d like to do is to use our findings to find new drugs that can be used against viruses. As I mentioned earlier, we are not promoting the use of antibiotics for all viral infections. However, if we can understand the molecules involved in inducing this antiviral state, we can actually make new drugs that can selectively kill viruses without affecting the bacteria, and that would be great to do.


12:16 - Changing Data Protection laws

How are online companies using our information?

Changing Data Protection laws
with Richard Clayton, Cambridge University Computer Laboratory

Now, we’re following the ongoing story of social media and our data use; Facebook CEO Mark Zuckerberg has been answering some very tough questions recently from US politicians in the wake of the announcement that information about millions of Facebook users was passed to a third party, Cambridge Analytica; this has got many of us thinking about how much companies like Facebook know about us, and how they are using that information. Part of the problem stems from the fact that the law has been slow to keep up with the pace of technology. But, on the 25th of May 2018, the European Union are going to introduce a raft of new data protection measures, called the General Data Protection Regulation or GDPR that will address some of these issues. Richard Clayton is a security researcher in the Cambridge University Computer Laboratory.

Richard - Facebook is basically an advertising company; they exist to make money, like all companies. They make money by putting adverts in front of people and they make more money if the adverts go in front of people who are interested in the topics of the adverts. And if people click on them, if people buy the products which are advertised and the more you know about people on your platform the better you can place the adverts.

Chris - One person pointed out - I think one of the US politicians who was questioning Mark Zuckerberg - pointed out that actually the reach of Facebook extends well beyond Facebook’s own website doesn’t it, because there are all these ‘like’ buttons all over the internet? On the Naked Scientists, for example, we could but we haven’t, but we could have a button saying ‘I like this,’ and that would tell Facebook that a person on that page likes that particular piece of content, which means Facebook is harvesting information about people from well beyond the scope of its own online realm.

Richard - Yes, indeed. And also many apps or many websites let you sign in using your Facebook credentials and, again, Facebook learns the information which comes from there. And indeed, certainly in the past, it’s been the position that if people signed in with Facebook then where you’d signed into was able to see information about the people who had then arrived on their particular site.

Chris - And the EU’s new approach to data protection, which is coming in shortly, will that have teeth and will it make a difference to this sort of behaviour?

Richard - It certainly has teeth and it has made a lot of companies concentrate very hard on whether or not they’re going to meet the new rules. Because fines under the GDPR can be up to 20 million Euros or 4% of global turnover, whichever is higher. And if you’re Facebook with an enormous global turnover, an eye watering amount of money which they risk if they don’t correctly behave under the new legislation.

Chris - One other interesting thing I noticed in reading the terms of the legislation is that it extends beyond the shores of Europe. So even if you’re not in the EU, if you are a company anywhere handling data from an EU citizen you’re potentially liable to that act.

Richard - It is even wider than that. Because it applies not just to EU citizens but anybody who happens to be in Europe. So, if you’re an American and you come to Europe you will suddenly get EU rights, which you would not have if you stayed in the United States and, effectively, that means that people are treating this as a global law.

Chris - It sounds like a jolly good thing doesn’t it? But what’s to stop someone going to a country that does not respect EU values, EU law, for instance Russia? There are various entities which are now based in Russia online, and they do that because they know they’re beyond the reach of various laws and so on.

Richard - That’s obviously a problem. But large companies tend to be multinational, so even if there are no engineers in the EU, then there may well be a sales operation here and therefore there’s money or there’s people that you can grab. We’ve seen in the case of people breaking laws like anti-spam legislation, that we can scoop them up at the airport when they go on holiday to Barcelona.

Chris - Even though the EU acts within Europe, are other countries, notwithstanding some that don’t want to, but are other countries signed up to this? So if a person in America does something which breeches EU rules, can the EU reach over to America and get them, or South America, or Australia?

Richard - Possibly not unless the come here. But, equally, the problem the EU sees is people behaving within the EU, and then the large multinationals, the household names, are that they produce appropriate systems and it’s quite clear that they’re going to. They’re doing a lot of engineering at the moment in order to make sure they meet the May deadline and you will get all sort of new rights. You’ll see new permission things popping up on screens; you’ll see that you can do new things like export all of your data.

Chris - But surely, if I’m a hacker and I break into your company and you’ve got a million peoples data on your computer, I steal it, I’m not going to give a toss about what the EU says I’ll just use that data anyway, but you will get the bill. So isn’t this kind of penalising the guys who are trying to do the right thing, even though there’s some people who don’t want to do the right thing, have actually done the wrong thing?

Richard - Not really. It’s penalising the people who’ve kept your data insecurely in such a way that people can break in and steal it. And the threat of the very large fines means that people are actually going to concentrate on this in an appropriate way.


Down to Earth: From Space to Selfies
with Stuart Higgins

What happens when the science and technology of space comes Down to Earth? Dr Stuart Higgins explores how the space race spawned the selfie…

Stuart - Welcome to Down to Earth from the Naked Scientists.The mini-series that explores the spinoffs from space technology that are being used in life on Earth. I’m Dr Stuart Higgins…

This episode, we’re talking about how the need to make better cameras for spacecraft gave us camera phones and selfies.

In the 1990s at the Jet Propulsion Laboratory in California, physicist and engineer Eric Fossum and his team were working on the problem of digital cameras for satellites. For years, satellites had been beaming back some of the most spectacular images of our universe, but the current technology was proving problematic.

At the time, early digital cameras used charge-coupled devices, other wise known as CCDs. In a CCD, each pixel is effectively a tiny square of  the material silicon. A voltage of light to the silicon pushes out charges leaving a charge free region at the surface. If a photon of light strikes this area, it generates an electrical charge. By varying the voltage between adjacent regions, this packet of charge is passed along the row of pixels until eventually it’s read by a circuit that converts the charges into a digital signal, which is used to make the digital image.

Whilst this technology is great for its high sensitivity, it was causing space scientists problems. The sensors used a lot of power and were sensitive to radiation that could cause ‘noise’ in the images. The scientists wanted a way to reduce the required power supply and radiation shielding to make the spacecraft lighter and, therefore, easier to get into space.

So Eric and his team set about developing a new technology called Active Pixel Sensors. Rather than passing the chargers from each pixel along a line, every pixel in an active pixel sensor has a tiny circuit that’s built into the back of it, which converts the light directly into a digital signal. These digital signals could be read out in parallel more quickly than in a CCD, and the overall circuit needs less power to operate.

The sensors could also be manufactured using the same production lines as silicon microprocessors enabling cheap production. Cheap, low power image sensors were initially used in webcams, but it was the advent of the camera phone that really allowed them to take off. The technology was spun out into a company led by engineer and entrepreneur Sabrina Khomeini, one of the team from the Jet Propulsion Laboratory.

It’s been licensed to major image sensor manufacturers in advance to the point where a smartphone in our pockets can now produce broadcast quality video and images. The ability to readily take photos has revolutionised the modern world, perhaps epitomised by the Oxford Dictionary’s 2013 word of the year - ‘selfie’.

So that’s how developing better cameras to put on satellites for space exploration led to the low cost, low power image sensors that are used in many of our modern devices.

20:59 - Ant-y Infection Control

How do insects stop infection from spreading?

Ant-y Infection Control
with Chris Pull, Royal Holloway University

This winter in the northern hemisphere hospitals and care homes have faced one of their worst flu seasons ever in terms of numbers. Transmission of respiratory illnesses tends to occur more readily in these sorts of places because there’s a high density of people so it’s easy for them to pass infections amongst themselves. But there are other classes of animals that also live in very high density and yet they’ve developed ingenious infection control strategies to ensure that this doesn’t happen to them. Chris Smith spoke to Chris Pull from Royal Holloway University who has been looking at what ants do.

Chris P - We know that social insects, so that’s ants, bees, wasps and termites, have evolved collective disease defences to try and control epidemics in their colonies, but a lot of the work so far has looked at how they prevent infections. So, for example, they groom another and they use antimicrobial disinfectants to prevent individuals which come into contact with pathogens from actually contracting an infection.

But what we wanted to know is how they actually prevent successful infections from spreading, so in cases where these sort of first line defences fail to prevent disease, what can a colony do to prevent the infection spreading to others?

Chris S - How do they know that they have an outbreak situation in the first place?

Chris P - What we’ve been able to show through our research using chemical analysis is that they can actually smell when another individual is sick. We’ve shown that sick individuals when they have an infection, and when you also inject them with an immune elicitor, increased cuticular hydrocarbons and this attracts the attention of ants in the colony and triggers a response.

Chris S - So this is like ant BO isn’t it, these cuticular hydrocarbons, that they can sniff on each other?

Chris P - Yes, exactly. They use them typically to tell if you are a member of the colony or not. We’ve been able to show now that they also change the immune response to infection and that can tell others who are sick.

Chris S - What is the situation when they pick up that this chemical trace or chemical signature of disease is there, how do they respond?

Chris P - It’s quite interesting that they have this multi-component behaviour. We were looking at infections in pupa, and the pupae are the developmental stage in between a larvae and and adult ant. They’re going through metamorphosis and they’re encased in these silk cocoons and what we found is that upon detecting an infection, the ants will break open this silk cocoon and then they start biting the infected pupa, and then they spray poison which is made up of formic acid and acetic acid from a gland at the end of their abdomen. This ensures that the fungus or pathogen growing inside the infected brood can’t grow anymore, so the acid seems to kill this fungus which is inside the body of the pupa. It seems like they do all this because the poison itself can’t penetrate into the body of the pupa unless the cocoon is removed, and unless they make these holes in the body of the pupa itself.

Chris S - Can you demonstrate that this really does mitigate or curtail the spread? So, in other words, if you were to abolish this behaviour it would be curtains for the colony?

Chris P - Yeah. We’ve actually been able to show by mimicking a situation where they fail to detect and destroy these infections. We simply kept ants with an infectious pupa; 40% of these groups of ants contracted the infection and became infectious themselves. You can imagine that in a full colony setup, that could very quickly lead to a huge mass breakout of this disease. But by performing these behaviours we saw that there was zero disease transmission.

Chris S - Do other social insects that have similar problems deal with it the same way or do they have a different strategy?

Chris P - We do see different strategies. In honey bees, because they live in these hives then they forage on the wing, what they can do is simply take the diseased brood out of the nest, fly away a few hundred metres and just drop it somewhere in the vegetation. Because they forage on plants and they forage for wide distances around the colony, the chances that they re-encounter those infectious corpse are really low.

The termites on the other hand, what they do is eat their dead. They live encased in these sort of pieces of wood which are rotting away and for them it’s hard to remove things from the wood because they live inside it, so what they tend to do is to eat their diseased individuals. But, at the end of the day they all use more or less a similar strategy, so they’re all trying to detect very early these infections and either remove or to destroy or to eat them before they have the chance to become infectious.

Chris S - That’s quite an undertaking strategy isn’t it, actually eating your dead? But how do you think this evolved in the first place because it’s quite a complicated behaviour isn’t it? It involves the ability to do chemical detection and recognition and then to have evolved a strategy that is itself successful in mitigating the threat.

Chris P - Yeah. We think that these behaviours have evolved because social insect colonies are like a superorganism, so they behave and the reproduce like a single organism in itself. In a way then, they’re very similar to a multicellular body like a frog or a human being and, in the same way when a human has an infected cell in its body you have this immune reaction to remove that infected cell. We see then common processes in multicellular organisms and these super-organismal insect societies. And we think that common evolutionary processes were at play during the evolution of both multicellular organisms and superorganisms and be able to detect and remove elements, which might harm the entire organism in itself were necessary prerequisites, or at least were necessary to evolve in order to ensure that you have the survival of the whole over its parts.

Biting into vegetable

How do we sense taste?
with Rebecca Ford, University of Nottingham

How does our tongue recognise a taste we like, like yummy chocolate, or dislike? Georgia Mills was joined by Rebecca Ford, an Assistant Professor of Sensory Science at the University of Nottingham.

Rebecca - It’s not surprise that it’s all happening in your mouth, but it probably will be quite surprising to you that there only just five basic tastes. For example, with your chocolate it will be the sweetness and the bitterness that are probably the most apparent. And if you look at your tongue in the mirror you can see lots of little tiny bumps along your tongue. The less red in colour to the rest of your tongue you’ve got a lot of them at the very tongue tip, the anterior part of the tongue, and these papillae, they house taste buds.

The taste buds are the term that we commonly know of and within those taste buds we have lots of taste receptor cells. As you chew your chocolate the tastants, so the sweetness from sugars and the bitter compounds they become dissolved in the saliva as you chew. These different compounds, they enter the taste pore of the taste bud on the tongue. There’s a little taste pore so as they get dissolved in the saliva they have to enter that taste pore, and then there’s a cascade of different reactions then that happens within the taste cell itself. It then sends a neural impulse up the nerves and then finally to the brain, to the gustatory cortex. The gustatory is the scientific name for taste essentially.

Georgia - Right. So there’s the things we can see when we go yuhh in front of the mirror and they house these taste bud, which then themselves house these little cells which respond to the various five tastes?

Rebecca - That’s exactly right.

Georgia - So what’s the difference between tasting something you like or you don’t like?

Rebecca - We’re actually all born with innate preferences to sense out things that are nutritive and non-nutritive; for example things that might be poisonous. But essentially, as we grow up and we learn these different things, what we like and what we dislike is very much about the brain. We detect things in the mouth but our brain then interprets those responses in terms of what we like and what we dislike.

Georgia - You mentioned the tasting part is very much happening on the tongue but the nose is involved as well, so what role does smell play?

Rebecca - It’s so important actually, and more important than people probably realise. It’s what we call taste-aroma interactions and normally, when you’re consuming some food you very very rarely will just have taste in isolation unless you were just adding a teaspoon of sugar into water, for example.

If we take the example of a strawberry. As you consume that strawberry, as you’re chewing it, you’re getting sugars released, you’re getting acids being released and they’re a sense of course in the mouth. But what’s happening at exactly the same time as you’re chewing, the aroma compounds are becoming airborne and they’re getting transported up to your olfactory bulb, which is very high up in your nose, at the base of your brain. The olfactory bulb senses the different aromas, and this is all happening at exactly the same time so your brain tells you it’s all happening in your mouth - it’s something that’s calle oral referral.

This is one of the reasons why when you’ve got a cold, nothing tastes quite right because it’s all happening in the brain. It’s exactly the same thing when you have one of those beautiful smelling fruit teas. they smell absolutely amazing  they’ve got this lovely strawberry aroma; when you drink it it’s just not quite right, and that’s because the sugar and the acids aren’t there.

Georgia - I’ve always wondered that. Fruit tea always smells so good and then you taste it it’s just a bit bland, isn’t it?

Rebecca - Of course, you’ve got all the aroma there, you’ve just not got the taste. So they’re so important; they go hand in hand.

Georgia - How do we tell one taste from another?

Rebecca - The majority of the evidence shows that each taste receptor cell is specifically tuned so it has one taste receptor on it’s membrane. Some are capable of detecting sweetness, those that are capable of detecting bitterness, umami, salty and sourness. So contrary to what you might have been taught at school where there are distinct parts of the tongue that are responsible for responding to different tastes, that is completely incorrect.

Within each of our taste buds we have taste receptor cells that are specifically tuned to each one of the tastes, but we have all of those taste receptor cells within a taste bud, and so essentially there isn’t that localisation that we were taught when we were at school. That was just down to a miscommunication of information unfortunately, from a paper that was published that was miscommunicating some findings.

Georgia - I remember that taste map well, and thinking it was a bit strange when you tasted sweets at different spots on your tongue and thinking this doesn’t seem quite right.

What’s in something to make your tongue respond and say this is bitter? Is it a different chemical, is it the shape of them; what’s different about them?

Rebecca - Exactly, it’s different chemical compounds; for example caffeine that’s in coffee, quinine that’s in tonic water, and then we have things like (10.39) acids that are  in beer. They are different chemical compounds and we have different bitter receptors all capable of receiving that information from those different chemical compounds, and then sending those signals to the brain telling us that it’s a bitter compound.

Whereas we tend to use tastes that are termed to describe everything that we are experiencing in our mouth when we consume things, which is a very complex scenario of lots of different signals that are being sent to the brain concurrently. We have taste being one of them; we have all those aromas that we were talking about being sent to the olfactory bulb in the nose. We also have all these texture receptors that are innovated all over the tongue and soft palate as well. They’re sending lots of different signals about the creaminess, the thickness, maybe the spiciness. And, of course, we have temperature receptors as well that give us information about the temperature of  the food or drink.

Georgia - Those five tastes you mentioned: bitter, salty, sweet, sour and umami - umami’s a brilliant word. But are those the only five tastes there are, is that everything?

Rebecca - At the moment… yes. But for something to be classified as a taste it’s got to be distinct from the other tastes, so it’s got to have stimuli that’s responsible from a taste that’s very different to the others. There’s got to be taste receptors that are able to send a signal to the brain, and there’s got to be perceptual independence from all the other taste qualities. So it’s got to be clearly identifiable essentially and all of those five basic tastes tick all of those boxes.

Now there are some other ones that have got a lot of evidence to suggest that they would be candidates for the sixth basic taste; for example fatty acids, carbohydrates, and this wonderful sounding taste that we know called kokumi.

Georgia - And another great word?

Rebecca - It is. And that really is an example of something that people describe as kind of a rich taste. It’s almost the way people describe it as like a mouth film, but it’s not very easily defined. And because it’s not clearly identifiable, that’s one of the reasons why we’re struggling at the moment to have enough data to say that it really ticks all of those boxes. Fatty acids, carbohydrates again, none of them quite meet all this criterial  although there’s a lot of scientific evidence that ticks some of those boxes.

A cup on its side, with coffee beans spilling out of it

34:33 - The evolution and genetics of taste

How has our taste developed over evolutionary time?

The evolution and genetics of taste
with Andrea Smith, University College London

How has our taste developed and evolved over time? And can we attribute our taste preferences to our genes? Chris Smith spoke to UCL’s Andrea Smith looks at how our genes and the environment we live in affect our food and drink preferences. So how might genes influence the process?

Andrea - It links back to the humans’ evolutionary origins where, when the human was still in prehistoric times, it was important for the human to taste and sense the environment where, ultimately, the ability to taste was acting as the perfect survival strategy. So being able to identify sweet tastes were incredibly important as they indicated food that is safe and will give you energy quickly. On the other hand, being able to taste bitter foods, and having evolved the taste receptors that identify bitter foods would indicate the foods that are poisonous and potentially harmful. And being able to detect them quickly would also select the individuals that could survive and procreate.

Chris - Indeed! Because lots of the chemicals, these plant alkaloids, that we try to avoid because they taste horrible are the ones that are poisonous. Things like deadly nightshade, the taste would not be good. But then again, there are some examples where we actually end up quite liking things that we should be averse to, shouldn’t we like caffeine is another plant alkaloid it’s there to poison insects, but we’re hooked on the stuff?

Andrea - And it’s every bitter! If you taste coffee for the first time it’s very very bitter and people don’t like it. But the interesting thing about when you drink coffee, over time we can learn to associate the kind of invigorating effect of caffeine and bitterness to feeling alert and we learn to like it.

Chris - Certainly I’ve learned to like it. I can endorse that comment. Given that in the modern era we don’t have the problem of not knowing where our next calorie’s coming from; we have supermarkets. We also tend to have someone watching out what we should and shouldn’t eat and we educate kids what to avoid and so on. Why do we still have these strong drivers towards what we do and don’t like?

Andrea - We unfortunately cannot change our DNA, so what we have been given and our universal ability to taste is still within us. And it’s also important to think about the fact that we have our DNA which has given us our receptors now in our environment. But there are many other influences that also shape what we like and do not like, so there are other sensors. In our environment right now, we do not only rely on our taste preferences and there are also genetic differences in sight and the pleasure pathways in our brain that still shape this behaviour. In our environment right now where we are being targeted by all these delicious foods, we’re essentially in this crazy environment where we are being exploited and our genetic tendency to like sweet and fatty foods is just completely expressed.

Chris - Do you know the genes which govern our intake in this way? And are there any populations who eat stuff which, compared with other populations, you’d think wow, they like that, why on Earth do they like that and you can pin their appeal for certain foodstuffs on a genetic cause?

Andrea - It’s more complex, unfortunately, than just having one single gene that regulates your food intake. It’s this whole storm of genetic differences, and a whole range of taste receptors that influence our behaviours. I think when you compare populations, it’s really important to think about what the foods and drinks are that people are exposed to, and their parents are exposed to, that explain these differences more that actually the genetics when you compare over time or between different cultures.

Chris - Andrea: personally, as I’ve got a bit older there are certain things that I detested when I was little and I actually quite like now I’ve got older. Now that can’t be genetic because I might be evolving a bit but I’m not evolving that quickly, so there must be more to this than just genes what we do and don’t like as we age?

Andrea - Indeed! Everybody is born with this underlying universal ability to taste, but it emphasises that our lifestyle behaviours and our environment also overrules and displaces these genetic influences over time. I think just touching back on the coffee, for example, which is a very bitter taste and most people when they first taste coffee really dislike bitterness. But, over time, when  they realise that drinking coffee gives you this feeling of being alert and having a lot of energy, you associate it with feeling great and you learn to love that bitterness.

Chris - So you think that, basically, you’re genes endow you with a sort of template of things you generically do and don’t like but then, as we go through life and we have life experiences, we can paint on that blank sheet, that blank canvas, if you like and so there are some things where we’ll override the genetic guidance because we’ve discovered it might be incompatible with what our genes are saying, but it’s quite nice?

Andrea - Yeah, exactly!

Chris - Any particular other examples you bring to mind - a personal one?

Andrea - Alcohol is also another typical example which a lot of people when they first drink alcohol it doesn’t taste great. I remember drinking beer or wine for the first time and I hated it and I thought I would never like it. But then, when you associate it for example also to a social situation - having a laugh with your friends - you start to really appreciate the flavour as well over time.

Chris - I don’t know, I never had any problem with that. Perhaps that explains a lot. But it also explains why we have some of the most expensive wines you can have sitting in the studio and we’re going to taste some later on.

Sweets in a jar

40:47 - Creating flavours in the lab

How do companies create the flavours we find in food?

Creating flavours in the lab
with Aalbert Remijn, Taste Flavourings

When it comes to eating food, chances are you’ll find yourself surrounded by flavours, especially when you’re having sweeties like I like to do. But how do companies create them in a lab? Izzie Clarke has been finding out.

Izzie - As a child I loved Roald Dahl's Charlie and the Chocolate Factory, and genuinely believed that it was only a matter of time for Willy Wonka's three course dinner chewing gum to hit the shelves and, obviously, I’m still waiting. So whilst a trip to Willy Wonka’s chocolate factory isn’t quite possible, Cambridge have their very own flavour factory. Aalbert Reming, the Managing Director of Taste Flavourings boiled their work down for me…

Aalbert - Flavours are mimicking real nature; we always use the example as a strawberry. In a strawberry there are certain chemical molecules that determine that the strawberry tastes what it is. It can either be a green one, it can be a very sweet one, it can be a ripe one and those molecules, that chemistry, basically we try to mimic in our industry so that people always have a strawberry flavoured product that always tastes the same. The flavours can be natural and non-natural or artificial.

What makes flavours natural is definition. We’re strongly regulated by the EU on what we can call natural and what is not. So some flavours are developed as natural flavours and use certain molecules which are natural and thereby become a natural flavour and other flavours don’t.

Izzie - Laid out in front of me were jars and jars of clear liquids, each a different flavour that Aalbert’s company use to create sweets, drinks, cakes, ice cream - you name it.

Aalbert - We’ve got a raspberry…

Izzie - All of my five a day!

Aalbert - Exactly, exactly.

Izzie - But, in addition to fruit, the team also create what they call ‘brown flavours.’ We’re talking coffee, toffee, butterscotch and my favourite - tiramisu.

Aalbert - Clearly, this has got coffee notes in and it’s got chocolate notes in.

Izzie - Oh my gosh, I’m definitely smelling coffee, and I’m definitely getting the sort of punch of an alcoholic element.

Aalbert - You can either start from scratch on these flavours or you can take a coffee flavour that you’ve already got, a chocolate flavour that you’ve already got, and start mixing things together, adding bits, and that’s the creative process that our flavourists use to make these flavours. Flavours deal with your smell. If you pinch your nose you don’t taste anything people say but, basically, what it is is the flavours that are volatile, there are molecules that kind of go airborne and go into your olfactory gland in the top of your nose basically don’t get perceived and, therefore, you don’t taste anything.

Izzie - We decided to put this whole smell/taste relation to the test.

Aalbert - Quite a lot of the flavour is ‘locked up,’ so to speak, in this gummy, so if you lick it and then you smell again, then you’ll find that you get a bit more odour off it than just smelling a dry sweet where most of the flavour is actually sitting on the inside.

Izzie - Let’s give this a go.... I actually can’t work it out. It’s citrus-y I think.

I’ll go straight in. Oh, it’s orange. It’s like a sweet orange. Mmm, it’s very yummy though.

Whilst I tucked into a few more sweets, Aalbert explained that they also come across a few challenging and rather bizarre flavour requests…

Aalbert - We’ve recently done an avocado. How do you describe an avocado: it’s a bit green, it’s a bit fatty and how do you mimic tha if somebody wants to stick it in a boiled sweet?

We’ve done a rancid flavour, so basically to make something taste a bit more rancid that is going off. I think it went into mayonnaise. I think, our customer who’s putting it in a mayonnaise wants that because their customers want it like that.

Izzie - Everyone’s taste is unique... I suppose. But how can flavour companies monitor what goes into their creations, and what if something isn’t quite right? It was off to the lab…

Are you able to talk me through this rather noisy equipment right here?  What is making that rather large hum?

Aalbert - The hum is a vacuum pump that creates a vacuum under which these mixtures get analysed; where we can run through flavour samples. The equipment breaks it down and refers what it finds to a database which gives us a rough idea on what’s in it, and at what quantities to make sure that we have included all the components that should be in. As soon as something comes out of the factory we run it through the machine, we pick up the previous batch of that product and we compare, so that’s one of the steps that we use to make sure that flavours are always correct and always in line with the previous sample.

Izzie - Aalbert is holding this tiny little tube; it looks a bit like an injection actually. And is that just so you can control these really tiny droplets that then get put into this rather large machine next to us now?

Aalbert - Yeah. The content of this injector is 10 microlitres.

Izzie - How much product would go into say one of these boiled sweets that we’ve seen?

Aalbert - That depends how strong the flavour is but also how strongly flavoured the customer wants it to be. Generally between 1 and 3 grams per thousand, so 1 kilo makes a ton of sweets.

Izzie - Gosh, so that’s not very much at all!

Aalbert - It’s not very much, no. It’s definitely the finishing touch. It’s definitely not part of the bulk of the food, it’s very small dose rates.

Izzie - Once the flavour has been analysed and given the all-clear, it’s then taken to the application lab, which is where these flavours in their liquid form are then put into something like a cake or gum. But when it comes to creating the perfect sweets it’s test, test, and retest…

Aalbert - We have more labs here. Things do change as they are applied in the end product. The end product, which are called the ‘matrix,’ does something to flavours. It can either enhance it or it might implode and it might disappear. It might not be powerful enough.

To give you an example: when we make hard boiled sweets, the boiling process does something to the flavour because the flavour is volatile because it needs to be volatile otherwise you don’t smell it, so you don’t taste it. So it gives us a better idea that maybe that will led to some further adjustments that we need to make.

Izzie - On the subject of sweets, sugar tax is something that comes up quite often, so is there a way that you could possibly make a sweet actually sweeter but not with as much sugar perhaps?

Aalbert - We’re talking here about the Holy Grail - sweet without sugar, fat without fat, salt without salt. With flavours they can definitely boost certain properties but you will never be able to mimic the mouthfeel of sugar, which in sweets is maybe as high as 80/90%, or in a drink where it is as high as 10%. So yes, you can tweek things, you can enhance things, but you can never replace it and you will always need the real thing too.

Glasses of Wine

48:09 - Cheers to the Science of Wine

The Naked Scientists pop some bottles... All in the name of science!

Cheers to the Science of Wine
with Clare Bryant, University of Cambridge

"A rich fruity body with hints of vanilla and a smooth chocolate texture layered over a long finish…” For many, wine tasting and wine appreciation sounds like a foreign language. But there are many different grape varieties, the climate where wine-making grapes grow makes a huge difference, and even the microbes that live in the soil around the roots of the vine also affect the flavour. To explore how and whether we really can pick up on these subtle and rather delicate vinicultural nuances, Chris Smith and Georgia Mills were joined by Clare Bryant, who as well as being an expert on how the immune system works, is also a wine specialist and surprise, surprise, she brought some beautiful samples with her.  So what’s actually going in the mouth when we taste wine?

Clare - We’re experiencing a very large, complex chemical reaction. There are about 400 aromas in wine, so that’s the nasal part of the procedure. In each wine there’s at least 27 different organic acids, 23 different types of alcohol, 80 acids in aldehydes, six in sugars, and a long list of vitamins and minerals to name but a few.

TASTE #1: The battle of the Chardonnays - Exploring “Mouthfeel”

Chris - You’re going to demonstrate some of the principles that are at play when we put wine in our mouth. You’ve got three little tests for us to do; what’s the first one?

Clare - The first one is to taste the difference between a taut and a fat wine.

Chris - Taut and fat?

Clare - Yes. Taute and fat.

Chris - Educated?

Clare - What I’m talking about is richness. Some wines taste rich than others and this is nicely illustrated with Chardonnay. Chardonnay’s a white wine grape, widely grown around the world. It is also very good at taking on the flavours of barrels and oak and various other things. So richness in Chardonnay can involve some or all of the following processes including the oak. Oak’s very important, it gives vanilla, toasty oak, that kind of flavour.  There’s also a malolactic fermentation, which is a secondary fermentation after the primary event which softens the acid. And it’s also yeast aging, which is where the residual yeast particles sort of self-implode, and they release some sugars and amino acids and that also causes richness as well.

Our first wine is a taut, modern Chardonnay. It’s from Margaret River.

Chris - Western Australia.

Clare - Western Australia indeed.

Chris - You’re decanting out little tastette for each of us - a little soupcon for Georgia and I to try.

Clare - If you smell the Chardonnay first of all you’ll…

Georgia - Oh, it’s very smokey.

Clare - It is smokey, yes. It is smokey; there is some oak in this wine. And you can smell a bit of citrus, you can smell some nutty oak, you can smell potentially the smokey struck match so that’s a good effort. And then if you taste it… You’ll find a lemon citrus and then moving over to a bit of dried stone fruit: pear, grapefruit, melon, fig.

Georgia - Mmm, it doesn’t quite taste how it smells. If it tasted like it smelt I think you’d be a bit... cough, cough, cough.

Clare - Yeah, correct.

Then you take the second version which comes from South Africa, so this is a Lanzerac Chardonnay from Stellenbosch.

Chris - It’s much less smelly; there’s much less to smell about this one.

Clare - That’s interesting.

Georgia - Stronger flavour as well.

Clare - It does, yeah.

Chris - It’s much stronger. It’s a bigger; it’s a fatter isn’t it?

Clare - It is.

Chris - It fills your mouth more.

Clare - That’s the point. It’s a fatter more oaked wine.

Chris - Is that the oak that’s done that, that’s given it that vanilla.

Clare - It is quite a big hit.

Chris - There’s a big vanilla hit there and it is fruity, but it’s interesting it smells less.

Clare - Yeah, it’s a more restrained smell.

Chris - So adding oak gives you those stronger flavours?

Clare - Yeah, and it’s a more heavily oaked wine than he first wine we tasted.

Georgia - Why doesn’t the strength of the smell match the strength of the flavour?

Clare - It doesn’t always do that. Sometimes it also depends upon how long you’ve had the wine in the glass, the age of the wine. There’s a variety of factors that influence the nose. That’s interesting because in my opinion South Africa are making some of the great Chardonnays in the world.

Chris - That won’t please the Aussies! The second wine?

TASTE #2: Comparing Rieslings - Aging of wine

Clare - The second one is we’re looking at bottle ageing. What happens is that the wine continues to react from birth to being in the bottle and this is really nicely illustrated by Riesling, which is another white wine grape. It’s generally light in alcohol and has a refreshing, high fruity natural acidity but, as it ages, it has the ability to take on petrol notes.

Chris - Really!

Clare - Like we put in the car.

Chris - I’ve hear this. What’s the octane rating of this.

Clare - Well not very high. It’s treated with trimethyl dihydronaphthalene and that…

Chris - But that’s in mothballs, isn’t it naphthalene?

Clare - Yes, absolutely. And it comes from some precursors that undergo acid hydrolysis. And the presence of these precursors really determines the wine’s ability to age and so a good Riesling will have these compounds to do this.

The first one is a young Riesling. It’s the Magpie Estate Rag and Bone Riesling made in 2017 so it is young. It’s got a lovely perfume nose if you smell it.

Georgia - It’s peachy.

Clare - It is. It’s limey…

Chris - You’ve got a very good nose Georgia, you should be into wine tasting.

Clare - You should.

Georgia - I am!

Chris - Not just amateur in your living room. Yes, you’re right.

Clare - Yeah, perfumed, limey, red apple nose, hence the pineapple.

Chris - That’s a nice wine. But you’re saying that’s a young wine?

Clare - That’s a young wine.

Chris - It’s not been in the bottle very long?

Clare - No. 2017. It’s a nice lively fruit, good acidity.

Chris - We’ll compare that with?

Clare - This is Peter Lierman Wigan Eden Valley Riesling; it was made in 2011. And if we give it a sniff…

Georgia - It really does smell of petrol. That’s so weird!

Clare - It really does. It’s even more kerosene than petrol actually.

Georgia - If I put a match in this, would it explode?

Clare - I’ve never tried that actually.

Chris - If I’m honest though, having tasted this I prefer the young one.

Clare - Yeah, that’s interesting.

Chris - Do people tend to break down into two camps.

Clare - Yeah it does divide people.

Chris - Why has sitting in the bottle done that?

Clare - It’s just literally an acid degradation of the keratin precursors, which then leads these precursors to take on the chemical that then gives you the sort of petrol-ly, diesel-ly type smell.

Chris - So there is this ongoing chemical process in the bottle?

Clare - Ongoing chemical process, yeah.

Chris - Is there a sort of rule of thumb as to when a good time to drink a wine is? Do we know how different wines age because sometimes it’s going to work, sometimes, it’s not going to work to keep them longer isn’t it?

Clare - It’s complicated. You can predict according to how wine is made and this is something that a lot of the winemakers specialise in. They’ll give you drinking dates and it very much depends upon the wine, the winemaker and the vineyard.

Chris - Shall we do our final test?

TASTE #3: Food Pairing: Red wine plus blue cheese

Clare - This time we’re looking at the combination of wine and food. We have a red wine: it’s a Ripasso Valpolicella. It’s an interesting wine because you partially dry the grapes first, then they ferment, and then they undergo a second fermentation.

Chris - Why should that make a difference the drying them?

Clare - The drying them increases the sugar.

Chris - Right.

Clare - So you get a sweeter wine and this has a sort of perfumed rich nose with some cherry and oak. And if you taste it… you get a kind of chocolate, spicy, bittery type taste.

Chris - Mmm. It’s certainly got the spice there.

Clare - You can taste the sugar as well.

Chris - Mmm. Peppery.

Clare - And now you take a piece of cheese.

Chris - We’re being proffered some Shropshire blue cheese.

Georgia - Oh no, blue cheese.

Chris - I actually really like blue cheese. It’s not a bad one.

Clare - And now try the wine again.

Georgia - Ooh!

Chris - Mmm. The wine is enhanced - the combination.

Clare - Umm the combination.

Georgia - It’s become sweeter, yeah.

Clare - It brings out the sweetness and it brings out the difference in the flavour and that’s because there’s two different effects going on. When you take the cheese: it’s fatty, it coats your mouth, it lubricates your mouth. Whereas the wine because of the tannings in the wine, they cause an astringency, and what that effectively is is the tanning molecules bind to the proteins in your mouth. This then makes your mouth feel dry and kind of puckers up your tongue and puckers up your cheeks, and reduces the lubricant proteins that are present in saliva. We’re having a combination of the oily lubricant with the astringency of the wine, you’re then arriving at a new balance, so you change the flavour of everything in your mouth at the time.


Catfish: Super-Taster of the Underwater World
with John Caprio, Louisiana State University

As it’s sense month, we’re celebrating the super sensors of the animal world! Here’s John Caprio from Louisiana State University who’s fished out a  case for super-tasters of the underwater realm... the Catfish!

John - Just looking at a catfish with its long, whisker-like growths and lack of body scales, you would never guess that it has a super power, the ability to actually taste its environment.

From its whiskers, which have the highest density, to its tail, the catfish is coated in taste buds, unlike a human whose taste buds are limited to inside its mouth.

A catfish is able to locate desirable food sources while avoiding bad-tasting materials in the water, even determining the direction of its food, all because it is a living, “swimming tongue.”
Izzie - Could you imagine being covered in taste buds? It’s the perfect super power if you’re walking around a bakery… Not so great if you’re in a public toilet though. So where can we find these swimming tongues?

John -  “Catfish” include approximately 3,000 species of true bony fish that possess characteristic protrusions from their head, termed whiskers, feelers or barbels.

Although some catfish live in saltwater, the majority of species are found in freshwater.

Some catfish have large eyes and live in clear waters whereas others have small, beady eyes, are bottom-dwelling & live in murky waters.

Adult catfish, depending upon the species, can be a few centimeters up to a few meters in length and many are quite tasty to humans.
Izzie - But, they’d probably taste the danger before you’d even got your fishing net out! But how do catfish taste their prey, before they’ve even caught it…? Back to John

John - A hungry catfish that is searching for dinner is attracted to amino acids, the building blocks of proteins. Those chemicals are naturally released by aquatic organisms, dissolve in the water and indicate the presence of nearby food.

With its taste bud-covered body, catfish can amazingly detect one part amino acid in a billion parts of water----which rivals the sensitivity of a shark nose!

By contrast, a human tongue is at least 100,000 times less sensitive to amino acids and to many other foods.

If we had to search for our meals using only our taste buds, we’d be hungry all the time.

The “swimming tongue” that is the catfish, meanwhile, would be eating well…unless, of course, its food happened to come with a fish hook!


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