Having grown up in a South Eastern European country, where fruits are abundant and make up probably about half of our diet during the summer, I’m used to many different kinds of fruit. However, a banana was probably the most exotic fruit that I came across until the age of about sixteen. So, I was pretty intrigued when a couple of months ago a friend of mine bought a mango for us to try. We googled ‘how to eat a mango’, cut it into those cute hedgehogs like they do and tasted it. But, since neither of us had ever tried this fruit before, we didn’t realise that it wasn’t ripe, so the taste was far from nice. Except for the part just around the pit it was like chewing on pine needles. Since then I have learned how to pick more or less ripe mangos and developed quite a taste for them but, I still can’t help noticing a hint of pine in the flavour. Every time this makes me ask myself, what is it that makes two plants that are so different in terms of their habitat and their taxonomic position taste or smell similar?
To get to the bottom of this lets start by looking at how the sense of taste operates and how it is linked to the sense of smell. The flavour of our food is determined by these two senses
combined: try holding your nose whilst eating, you’ll find even familiar foods don’t taste right. Our tongue, the roof, sides and the back of our mouth are covered with taste buds – small receptors sensitive to so called flavorants. The receptors that allow us to detect and recognise odors are somewhat similar to these taste receptors. The two systems rely on chemoreception, which means that the receptors involved are able to capture the chemical compounds that make up a certain smell or taste and transform this information into a nerve impulses in the brain. Information regarding both taste and smell combine in your brain allowing you to enjoy a multi-sensory flavour experience.
Now back to the mango/pine problem. I decided to start my investigation by finding out what chemicals produce the familiar smell of pine. A quick trip to the nearest pharmacy and a scan through the ingredients of pine-scented essential oils revealed that the main components were: α-pinene, β-pinene, limonene, myrcene, camphene cadinene with very little variation from one brand to another. These compounds belong to a larger group known as terpenes, or more precisely monoterpenes, which are most commonly, but not exclusively, found in the resin of coniferous trees.
More than thirty different chemicals make up the flavour of mango and, surprisingly enough, α-pinene, β-pinene, limonene, myrcene and camphene are among them. So, five out of six compounds that are found in pine needles are also found in mango pulp.
Due to their strong smell, high viscosity and antiseptic properties, terpenes act as a repellent that drives away herbivores and insects, thus protecting the plant from predation. The native land for mangos is South and South East Asia and, while there are several varieties of pines that grow in the same part of the world, these plants are only distantly related. Pines are gymnosperms – even though they produce seeds, they develop neither a flower nor a fruit. Mangos on the other hand are flowering plants. From an evolutionary point of view they are considered to be more advanced than gymnosperms since they have flowers that facilitate pollination and their seed is protected by a fruit. Flowering plants diverged from gymnosperms more that 200 million years ago. So how did such different plants develop such a similar defense mechanism?
The first thing that pops to mind is convergent evolution. It is very common in nature for different animals which occupy very different habitats and never even come near each other to develop similar adaptations when faced with a similar obstacle. A classic example is the structure of an eye of vertebrates (e.g. mammals) and cephalopods (e.g. octopus): both these groups have independently developed camera eyes astonishingly similar in their structure and way of functioning. Therefore, an efficient system is very likely to develop in parallel across unrelated species.
So, in the case of pines and mangos, terpenes provide not only a reliable defense against predators but also a mind-bending taste anomaly.
Guest Post by: Daria Chirirta.
Originally from Moldova, I am currently in my second year at university in France, Université Jean Monnet , St Etienne, studying Biology. My scientific interests include Molecular Biology and Genetics, in which I am hoping to pursue a Master’s degree. Other than that I enjoy learning and speaking foreign languages, knitting and cinema.