by John Knight, PhD
Chemical Curiosities is an audio companion to John Knight’s Substack, featuring pieces that explore the molecules behind everyday life, with a touch of organic chemistry. From historical pigments and natural dyes to the chemistry of smells, flavors, and unusual phenomena, each episode reveals a small but fascinating piece of the chemical world. https://johnknightphd.substack.com/ <br/><br/><a href="https://johnknightphd.substack.com?utm_medium=podcast">johnknightphd.substack.com</a>
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August 10, 2026
<p>The Myth of Bananas and Bees</p><p>Imagine you’re watching a movie. On the screen, some kids are walking down the sidewalk in a typical American neighborhood. They’re eating bananas, and, like all suburban kids on summer vacation, they’re laughing and having fun. Little do they know that there’s danger! </p><p>Unfortunately, there’s a large honey bee colony tucked up in a nearby tree cavity. At first the bees are calm, but as soon as the kids walk under the tree with half-eaten bananas in their hands, things quickly change. The bees become agitated. Something makes them angry. Suddenly, one of the kids hears a buzz and a sudden sharp pain in an arm. Before the children can even react, bees are swarming all around them. The stings come in quick succession. Panicked screams fill the air. </p><p>From across the street, a kind, elderly lady hears the commotion and comes outside to see what’s going on. Her face is at first confused, but it quickly turns to absolute fear when she sees what’s happened. Her loud cry is all you hear as the scene fades to black. It sounds like something right out of a horror movie.</p><p>You might think it’s crazy, but there’s a popular myth about bananas and bees. Supposedly, if you eat or hold a ripe banana near a beehive, chemicals in the bananas will drive the bees into an aggressive frenzy. A local beekeeper might even give you a warning to never eat bananas around honey bees! Of course, it’s not really accurate. But there is a kernel of truth. I’m John Knight, by the way, and this is where I dig into the chemistry hiding in ordinary things. As always, full transcript and visuals are in the full post on my Substack.</p><p>The molecule behind it all is called <a target="_blank" href="https://en.wikipedia.org/wiki/Isoamyl_acetate"><strong>isoamyl acetate</strong></a>. It’s found in ripening fruits and special styles of beer. It even plays a role in how honey bees spread the alarm. Holding a banana near a beehive won’t switch the colony into “Attack!” mode, though. Bees are too sophisticated to rely on a single molecular trigger common in nature. Instead, they respond to context, just like we do!</p><p><p><strong>Love the intersection of nature, history, and chemistry?</strong> Subscribe for free to join me as I unpack the molecules shaping our world from beehive security to the smell of the ocean.</p></p><p>Enter Isoamyl Acetate </p><p>Before I continue, let’s take a moment to explain what isoamyl acetate is. First, it’s an <a target="_blank" href="https://en.wikipedia.org/wiki/Ester">ester</a>, and it belongs to the family of organic molecules famous for providing rich, fruity, and floral aromas. Without esters, the world would be a pretty boring place!</p><p>Like all esters, isoamyl acetate is made from two components: a five-carbon molecule called isoamyl alcohol and acetic acid - that’s the acid found in vinegar, by the way. In its pure form, this volatile ester smells remarkably like banana candy and, to some people, like ripe pears. It’s found throughout nature, too. The human nose can even detect it at tiny concentrations in the parts-per-million (ppm) range. I included a chemical structure in the full post on Substack if you’re interested.</p><p>So, sure, it smells nice, but what does this molecule have to do with bees? To answer that question, we first need to talk about the time of year when bees are the most sensitive to their environment. </p><p>The Late Summer Dearth</p><p>That time is late summer and early fall. Depending on your location, August or September, for example. At this point, the honey bee colony is at peak population. Their comb is filled with honey for the winter season. But now food is scarce. The blooms of spring and summer are long gone. Depending on the area, there might be nothing to bring into the hive until March or April. This is called the late summer <a target="_blank" href="https://www.merriam-webster.com/dictionary/dearth"><strong>dearth</strong></a>. </p><p>To survive, the colony needs to prioritize. The population begins declining. The queen lays eggs for winter bees. Instead of being bred for work in the warm season and living 4 to 6 weeks, these bees will be bred for endurance, surviving up to six months thanks to their higher stores of fat and protein. They will be the bees that take the colony into the new year with the queen. Those summer workers? They won’t make it past the fall.</p><p>Until winter arrives, though, the colony fiercely protects its honey.</p><p>Suddenly, what was acceptable earlier in the year is now prohibited. Everything is scrutinized. In the spring, a drifting bee might find its way into another hive without issue. Now, the guards shut her out. Things might even get physical. Protecting the colony and its honey is a matter of survival. And the threats have never been greater: robber bees, wasps/hornets, and honey-hungry animals can easily destroy a smaller or weaker colony before winter even arrives. </p><p>Not surprisingly, this is a common time of year for bee stings. The bees are on high alert, and even beekeepers notice the change. A colony that was calm and easy to manage in the spring is now aggravated and temperamental. </p><p>These environmental changes also change how bees respond to the chemical signals they receive. </p><p>A 40-Compound Battle Cry</p><p>Imagine there’s a colony of bees in a tree, except this time, a group of foreign bees shows up at the entrance. These are called robber bees. They aren’t there to pay a visit or say hello. They are there to ransack the place. The specialized guard bees instantly respond, blocking their path. Wings and hair are pulled. Physical fights break out. As a guard bee drives her stinger into an intruder, a chemical flare goes off. </p><p>Honey bees have a special gland near the base of their stinger called the <a target="_blank" href="https://en.wikipedia.org/wiki/Koschevnikov_gland">Koschevnikov gland</a>. When a bee stings, this organ releases a complex cocktail of over forty compounds into the air. Isoamyl acetate is one of the most abundant and most active of these chemicals. It creates a sort of beacon, invisible to the eye, but easily detected by other bees, marking the victim for the rest of the colony’s guards. What this mixture does to the bee’s brain, though, is where things get really interesting. </p><p>When other guard bees sense this defensive concoction, the chemistry in their brain begins to change. Neurotransmitters like <a target="_blank" href="https://en.wikipedia.org/wiki/Dopamine">dopamine</a> and <a target="_blank" href="https://en.wikipedia.org/wiki/Serotonin">serotonin</a> spike, driving up aggression and lowering the threshold for attack. At the same time, a kind of endogenous opioid response occurs - that’s just a fancy way of saying the bee’s body produces its own natural painkiller. By dulling any sensations of pain, the guard has an advantage in a fight to the death to protect the hive. </p><p>And the mixture is important. The bees don’t respond to just isoamyl acetate. They respond to a mixture containing isoamyl acetate. The context is important!</p><p>As a side note, anything that blocks these chemical signals will help keep the bees calm. Beekeepers often use smoke when inspecting their colonies, and this smoke effectively prevents them from “hearing” any alarm.</p><p>It Used to Smell Like Pears</p><p>At this point, I think it’s important to mention that scientists only discovered the role of isoamyl acetate and other honey bee alarm pheromones in 1962. We’ve known about the ester for significantly longer, though. In fact, chemists have been synthesizing it for various purposes since the mid-19th century, back when it was all but impossible to isolate it from nature. They did this by reacting acetic acid with fusel oil - the unpleasant, toxic leftover from alcohol distillation. What they created was distinctly sweet and fruity. </p><p>And that brings us to the other thing that isoamyl acetate is so strongly linked to: bananas. The connection between the fruit and the isoamyl acetate is ingrained in our modern minds. I’m willing to bet that if I had a vial of pure isoamyl acetate and removed the cap, you’d immediately think of bananas or banana-flavored candy upon smelling it. But the ester hasn’t always been so strongly linked to bananas, especially when few people had any idea what bananas smelled or tasted like. </p><p>In 1851, the public actually got its first “taste” of synthetic isoamyl acetate at the Crystal Palace Exhibition in London. Here, it was shown off as a flavoring agent called “pear drops.” That’s right, I said pears! One of the judges at the exhibition actually noted that the flavoring agent reminded him of <a target="_blank" href="https://www.rhs.org.uk/plants/65237/pyrus-communis-jargonelle-d/details">Jargonelle</a> pears, an aromatic variety of European pear growing in the British Isles. For many years afterwards, chemists linked isoamyl acetate’s smell to pears, and consumers in Europe would first buy it as Jargonelle pear flavoring. </p><p>Things changed after synthetic isoamyl acetate entered the American market, however. American consumers, it turns out, weren’t very familiar with Jargonelle pears - they were a British pear, after all. Coincidentally, Americans became a bit crazed over an exotic tropical fruit called the banana. Bananas were very rare, and most Americans had never seen, let alone tasted, one. But they had heard of it! So, chemical suppliers in America began marketing isoamyl acetate as a kind of “banana essence.” And thus, the connection was made. </p><p>For Americans, this molecule has always been linked to bananas. Good luck convincing anyone that it smells like another fruit! </p><p>Where Else Does It Hide?</p><p>If you’re someone who is scared to death of bees and hates bananas, you still have likely met isoamyl acetate before. It’s a common component in other fruits like apples, peaches, and guavas. Even tomatoes have a small amount of the ester! One of the most striking, non-food examples, though, would be alcoholic drinks.</p><p>In Bavaria, Germany, beers made from malted wheat are common. A famous example is the <a target="_blank" href="https://en.wikipedia.org/wiki/Wheat_beer"><strong>hefeweizen</strong></a>, a straw-colored, cloudy-looking beer with a thick head of foam and a somewhat spicy aroma. And it also smells like bananas thanks to isoamyl acetate. How does that even happen? Do they just add it to the finished beer? It turns out that it’s natural. Yeast often produce esters when they ferment sugars. They basically make it the same way extract producers do today. A certain variety of yeast will, <a target="_blank" href="https://knowledge.escarpmentlabs.com/article/340-controlling-esters-in-wit-and-weizen-yeasts">under the right conditions</a>, favor some esters over others, though. Add just the right amount of yeast and keep the fermentation temperature warmer, for example, and a brewer can create a beer that smells a bit like banana candy.</p><p>A classic hefeweizen, of course, isn’t supposed to taste like a banana grenade exploded in the bottle. It takes some effort to find the right balance of classic wheat beer notes, spice, and banana. Many homebrewers have been disappointed by beers that either had no banana at all or too much. </p><p>Isoamyl acetate also shows up in other drinks. It can play a small but important background role in the aroma and flavor of drinks like wine, whisky, and even sake. It’s seemingly everywhere!</p><p>The “Lost Banana” Legend</p><p>Now, there’s one more myth I want to address about isoamyl acetate and bananas. People have realized for a long time that banana flavoring doesn’t smell or taste exactly like real bananas, so some have tried to explain the discrepancy. There’s a popular internet myth that banana flavoring is different because it was based on a “lost” banana variety that was common until the 1950s. </p><p>Today’s supermarket produce sections contain <a target="_blank" href="https://en.wikipedia.org/wiki/Cavendish_banana"><strong>Cavendish bananas</strong></a>. The Cavendish is cheap, easy to grow, and safe to transport. But it wasn’t always the dominant banana. Back in the early 20th century, another banana was king of produce: the <a target="_blank" href="https://en.wikipedia.org/wiki/Gros_Michel"><strong>Gros Michel banana</strong></a><strong> </strong>(also known as ‘Big Mike’). It was sweeter and denser than today’s banana. The aroma was floral and less complex, as well. Unfortunately, a fungal disease called <a target="_blank" href="https://en.wikipedia.org/wiki/Panama_disease#">Panama Disease </a>nearly wiped out this variety. It’s not extinct, but you’ll be hard-pressed to find anything but a Cavendish unless you live in particular regions. </p><p>Many people believe that the Gros Michel banana is the source of “banana flavoring.” It’s a romantic idea: a long-lost variety of fruit whose only remnant is the flavor of banana Laffy Taffy or circus peanuts, but it’s completely false. Gros Michel bananas do, in fact, have higher levels of isoamyl acetate than Cavendish bananas, with fewer competing aromas to hide it. To a human nose, isoamyl acetate seems to take center stage! Cavendish bananas, by comparison, seem “busier.” They contain other aromatic compounds such as <a target="_blank" href="https://en.wikipedia.org/wiki/Eugenol">eugenol</a>, which adds a distinct, spicy clove note that masks the isoamyl acetate. The boring, everyday Cavendish actually has more interesting chemistry!</p><p>In the end, the reason a Gros Michel banana tastes more like banana candy is a coincidence. It has more isoamyl acetate, but chemists were producing and selling “Banana Flavoring” before most people had even seen a banana.</p><p>It’s All About Context</p><p>Regardless of whether we’re talking about bananas of the past, yellow Laffy Taffy, or a cloudy German hefeweizen, we’ve learned to associate a molecule like isoamyl acetate with fruit and sweetness. But we are not the only ones who pay attention to this ester. How a creature interprets it comes down to context.</p><p>To a honey bee, isoamyl acetate isn’t about flavor at all. It’s part of a signal to rally the troops, so to speak, to protect the colony. In a different context, all by itself, it’s just another ambient ester found throughout nature. If a bee responds to a ripe banana, it probably thinks it’s found a food source. </p><p>One molecule. Seven carbons. It’s more than a synthetic molecule in a vial. It makes fruit enticing, adds nostalgia to your candy, and gives a wheat beer a special touch. For one species, it’s part of a rallying cry. For another, it’s just a byproduct of living life. </p><p>That’s the amazing context in which chemistry exists. How we experience that chemistry is just as important as what that chemistry is. Think about that next time you’re eating a banana or enjoying some honey!</p><p>I hope you found something interesting from this. If you want the transcript for everything I’ve said along with some visuals, check out the full post on my Substack. Thanks for listening, and I’ll catch you next time!</p><p><strong>References and Notes</strong></p> <br/><br/>This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit <a href="https://johnknightphd.substack.com?utm_medium=podcast&utm_campaign=CTA_1">johnknightphd.substack.com</a>
July 14, 2026
<p>Two Experiences, One Molecule</p><p>Picture this. You’re sitting at a picnic table on a hot summer’s day. Your friend hands you a cold beer - something light and refreshing. The perfect “lawnmower beer.” You pop the cap, bring it to your mouth, and your nose is immediately hit with the smell of malted grain and a hint of sweet corn. It’s a great combination!</p><p>Next, imagine you’re standing in a friend’s kitchen. There’s a pot of cabbage on the stove. Unfortunately, your friend has overcooked the greens. Perhaps they got distracted; now the kitchen is filled with an unpleasant, pungent aroma that reminds you of, well, really bad cabbage. </p><p>Two different experiences. Two different scents. But both come from the same molecule!</p><p>That molecule is <a target="_blank" href="https://en.wikipedia.org/wiki/Dimethyl_sulfide"><strong>dimethyl sulfide (or DMS)</strong></a>. It’s the same molecule I featured in my recent post about the smell of the ocean. DMS goes way beyond the sea, however. Once you start looking for it, you can’t stop finding it! I’m John Knight, by the way, and this is where I dig into the chemistry hiding in ordinary things. As always, full transcript and visuals are on my Substack.</p><p><p>Like what you’re reading? Subscribe to learn more about the chemistry and science in ordinary, everyday things!</p></p><p>Culinary Chemistry</p><p>Here’s a fun fact. You’ve probably smelled DMS today. You almost certainly have eaten it this week. Multiple times, in fact. And I bet that you had no idea!</p><p>Here’s the basic mechanism: a lot of vegetables and fruits - beets, tomatoes, corn, asparagus, and berries - carry a special molecule, something called <a target="_blank" href="https://en.wikipedia.org/wiki/S-Methylmethionine"><strong>S-methylmethionine (or SMM)</strong></a>. We don’t really know for sure why many plants produce it. On its own, this molecule is colorless and odorless. If you heat it, though, or let it sit too long, it breaks down into DMS. Milk and cheese do something similar, too. It’s what happened in that pot of overcooked cabbage we mentioned earlier. </p><p>By cooking that cabbage too long, we’ve liberated the very same molecule that helps give the ocean its smell. </p><p>Some foods get their DMS differently, however. </p><p>If you read my article about the smell of the sea, you’ll remember where it comes from: phytoplankton make a protective compound, they die, and bacteria break that compound down. You might have an idea of where this is going. This whole process isn’t just limited to phytoplankton and bacteria, though. It happens in the sea creatures that live and feast on the plankton, too. </p><p>Those lovely oysters you ate over the weekend? They probably had a sweet, briny aroma and taste that comes from trace amounts of DMS. In fact, a little DMS is one of the things people love about seafood. Things can go a bit too far, though. If you don’t store that seafood properly or let bacteria have their way, too much DMS will be formed, and you’ll be sending that seafood back to the kitchen.</p><p>Oh, and for those of you who are into expensive delicacies, consider the truffle. No, I don’t mean the chocolate. I mean the rare, intensely earthy fungus that commands a high price. If you like the way they taste and smell, you can thank DMS! In fact, truffles owe their highly prized aroma to DMS, and truffle-hunting animals likely use DMS to help search for the fungus.</p><p>That’s it for the kitchen! Remember that beer from the beginning, though? The one that seemed so perfect on a hot summer’s day? It turns out that DMS isn’t just something that sneaks into your food. Sometimes, it’s exactly what you’re paying for. </p><p><strong>The Brewer and Winemaker’s Dilemma</strong></p><p>DMS, it turns out, is a big deal in beer brewing. This really isn’t surprising considering that beer is made from malted grain, which also contains SMM - just like those fruits and vegetables I mentioned earlier! For most beer styles, however, the presence of DMS is considered a flaw. Imagine if your beer had an unusual sweet aroma mixed with cooked cabbage and may even spoiled onions. Doesn’t sound too appealing, does it? DMS is especially an issue for beers made with lightly kilned malts that contain higher amounts of SMM. Brewers make an effort to remove it by boiling the unfermented wort to drive away any DMS and by controlling fermentation conditions. There are a few exceptions, however. Some of you have probably had a cream ale or a German-style pale lager that had a hint of sweet corn. That was no accident! In these styles, a little DMS is a positive thing. Brewers of these styles typically have to adjust their brewing technique to keep just the right amount of DMS in the finished beer.</p><p>Beer isn’t the only alcoholic drink where the amount of DMS can make or break the experience. Winemakers also have to worry about it. The difference for wine, however, is that most of this DMS is produced slowly over time. Just as before, a tiny amount of DMS can enhance the fruitiness and complexity of a wine. It keeps developing over time, though, even inside a sealed bottle. Store that bottle the wrong way or let the wine age too long, and you’ll probably end up thinking the winemakers kept their socks on before they stomped on the grapes. </p><p>So far, everything we’ve talked about is related to smell and taste - things that we humans try to manage like brewers boiling off DMS or winemakers hoping you store that bottle correctly. We’re not the only species that notice this molecule, however. For some animals, DMS is a matter of finding food or being fooled into doing something. </p><p><strong>The Marine Scent Trail</strong></p><p>If you’ve been near or on the ocean, you’ve seen it before: seabirds circling above the waves as if searching for something. They seem to know the best spots for foraging, as though they have some kind of hidden sight. It turns out they don’t - they just know how to use DMS as a cue! DMS levels tend to be higher in areas where zooplankton are actively grazing on phytoplankton, which also happen to be the best feeding grounds for some seabirds. And birds like the albatross and petrel are exceptionally good at detecting DMS.</p><p>In a way, nature has developed an elegant system: just follow the scent trail to dinner!</p><p>This ability does have a downside in our modern world, though. Remember how I mentioned earlier that DMS in the ocean is formed by phytoplankton, bacteria, and algae living their lives? They especially like to do this on floating plastic, creating a biofilm on the debris that also produces higher levels of DMS. Seabirds, in turn, are drawn to these areas to forage. Inevitably, they end up eating smaller pieces of plastic, which to them smell exactly like their normal food. This is a major driver of plastic consumption in animal species that hunt by smell, and it’s largely something we humans have caused. </p><p>Bringing It All Together</p><p>Here’s the interesting part, though. A seabird’s nose can’t tell the difference between the krill it normally eats and a floating piece of plastic that smells like that krill. We humans are no different. Our noses aren’t just sensitive to the presence of DMS. They’re sensitive to the concentration of DMS. Depending on what that concentration is, the signal we get could be a delicious dinner or something dangerous. We’ve evolved to associate high levels of DMS with danger because it’s a chemical marker for death, decay, and maybe toxicity. In tiny amounts, however, it can come across as a good thing!</p><p>Think about everything we’ve covered. A little DMS in a cream ale is refreshing. Too much, and the brewer might consider that batch ruined. A hint of it in a nice red wine comes across as fruity and complex. Age it too long, however, and you might have a bouquet of stewed fruits. It’s the difference between a perfect oyster and a sickly, spoiled one. Again, the molecule in question isn’t changing. It’s not reacting or interacting differently. The only thing changing is the concentration. </p><p>A Little Bit of Cosmic Chemistry</p><p>Let me tell you one more thing before I go. Earlier this year, the James Webb Space Telescope detected a faint signal on an exoplanet called <a target="_blank" href="https://en.wikipedia.org/wiki/K2-18b">K2-18b</a>. This planet is located over 124 light-years away and orbits a small red dwarf star in the constellation Leo. Why do I mention this? Because the signal detected appeared consistent with DMS, and we know how connected that molecule is with life.</p><p>Now, the result is tentative. Astrophysicists are still debating whether the signal is really DMS or an overlap of other signals. Maybe the signal is just from a mixture of common gases such as methane and carbon dioxide. But just the possibility it was due to DMS was enough to get people excited. It’s also a reminder, though, that DMS is not just a terrestrial molecule. We’ve detected it in space and <a target="_blank" href="https://www.science.org/content/article/what-presumed-sign-life-doing-dead-comet">even on comets</a>. It might be far more common in the universe than we originally thought. </p><p>Outro</p><p>And that’s dimethyl sulfide. It’s in your kitchen, on your dinner table, and in space. Think about it the next time you have a beer or your fancy friend serves truffles at dinner. If you want the transcript for this along with some visuals, check out the full post on my Substack. Thanks for listening, and I’ll catch you next time!</p><p><strong>References and Notes</strong></p> <br/><br/>This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit <a href="https://johnknightphd.substack.com?utm_medium=podcast&utm_campaign=CTA_1">johnknightphd.substack.com</a>
May 12, 2026
<p><strong>Full post can be read at: </strong><a target="_blank" href="https://johnknightphd.substack.com"><strong>https://johnknightphd.substack.com</strong></a><strong>/</strong><strong>Intro</strong></p><p>Imagine a beautiful spring morning. The trees are stunning with new, bright green growth and colorful blossoms. Songbirds fill the air with their melodies. Above, small white clouds drift by across the blue sky.</p><p>Now imagine feeling the warmth of a mug in your hands as you take in this scene. What’s in the cup? For some, it might be a nice cup of coffee. Others might prefer something herbal or fruity. Still others would drink tea - green tea perhaps!</p><p>And what if that green tea actually tasted like cherry blossoms?</p><p>Hello everyone! My name is John Knight. As a chemist and writer, my goal for these audio posts is to peel back the curtain on the chemistry of our modern world. Whether it’s the latest lab breakthrough or the hidden science in our daily lives, I’m here to help break down the science so that it’s clear without getting bogged down in a bunch of lab notes.</p><p>Before I tell you about a very special kind of tea, just a quick reminder: if you’re listening to the audio-only version, be sure to check out the full post on my Substack. There, you’ll find a transcript of everything I’m saying and important visuals, some of which can help you “see” the chemistry I will discuss.</p><p>And now, let’s talk about a tea that was rejected by the industrial tea world of Japan, although it tastes like one of the most Japanese things of all…</p><p><strong>The Fleeting Scent of Spring</strong></p><p><a target="_blank" href="https://en.wikipedia.org/wiki/Cherry_blossom">Cherry blossoms</a>, or <a target="_blank" href="https://en.wikipedia.org/wiki/Cherry_blossom">sakura</a> in Japanese, are deeply connected to the spring season. The trees are prized for their beautiful flowers that come in shades of white or pink. For many, they are a symbol of renewal and the end of winter. Tourists will often flock to areas with many cherry blossom trees. Just ask anyone who has traveled to Japan or Washington, D.C. at the beginning of spring!</p><p>These trees are also a symbol of impermanence. Because they only bloom for one or two weeks on average, their beauty is but temporary, much like spring itself.</p><p>In Japan, sakura are more than just ornamental flowers, however. They actually have a long history of being used in confectionery and seasonal food. Flavor-wise, they are often described as a combination of floral, vanilla, almond, and light cherry notes.</p><p>This might be confusing to some who have stood close to a cherry blossom tree. If you put your nose right up to a flower, you will probably smell nothing. They are perfectly edible, but you probably won’t taste anything, either. Instead, the flavor is locked up in the flower, and a little chemistry is required to release it.</p><p>So how does this work? The flowers are traditionally cured through a kind of pickling process. First, the flowers are washed, dried, and mixed with sea salt to remove moisture. This is followed by a thorough soaking in a vinegar made from plums. This not only preserves the flowers and gives them a vibrant pink color but also changes their flavor.</p><p>Sunlight and Sugar</p><p>Many plants produce compounds called glycosides, sugar-containing molecules that also contain a non-sugar component. In addition to regulating plant growth and stabilizing pigment molecules, glycosides are also used to store potentially toxic or unstable molecules meant to protect the plant. Plants also produce special enzymes that can break down these glycosides into their individual components when needed.</p><p>For cherry blossoms, one important glycoside is <strong>o-coumaric acid glucoside</strong>. That name might sound scary, but bear with me for a moment. Think of this glycoside as a large storage molecule with an important component safely secured inside. On the tree, this glycoside and its unlocking enzyme are never stored in the same place. After harvesting, washing, and curing, however, many of the cells in the flower are broken, allowing the enzyme and glycoside to interact. The enzyme then breaks the glycoside into two molecules: <a target="_blank" href="https://en.wikipedia.org/wiki/O-Coumaric_acid"><strong>o-coumaric acid</strong></a> and glucose. From there, the rest of the chemistry can happen relatively quickly. That coumaric acid is a rigid, elongated molecule containing what chemists call a trans double bond. Normally, this would be stable, but in this case, it’s not. Add just the right amount of energy into that double bond, and it can be converted into a cis double bond, bending the molecule toward itself. It turns out that ultraviolet light (UV) from the Sun provides the necessary energy to do this. Once the geometry changes, the molecule essentially folds in on itself, placing the atoms in the right position to react and form an important molecule called coumarin.</p><p>It’s coumarin that is primarily responsible for that sweet, vanilla-almond flavor and scent of sakura.</p><p>But what does all of this have to do with green tea? That’s a completely different type of plant! And traditional green tea doesn’t contain fermented flower petals…</p><p>It turns out that this process of making coumarin also occurs during tea production, albeit in very small amounts. For one particular variety, however, this isn’t the case.</p><p><strong>Japanese Green Tea</strong></p><p>Many people have a basic understanding of where tea comes from, though they may not be aware of the exact details. Most of the tea consumed in the world is made from the leaves of the tea tree (Camellia sinensis). That’s right - the tea tree is in the same family as all of those glossy, evergreen shrubs that produce bright, showy flowers from fall to spring every year. The processing of the leaves varies considerably from country to country and even region to region. For every producer that uses modern methods of harvesting and processing, it’s not difficult to find some who make tea using more traditional methods and maybe even entirely by hand.</p><p>Although China is the biggest producer of green tea in the world, Japan also produces its share. It’s also very distinct. When making green tea, it’s important to stop oxidation by enzymes in the leaves. Otherwise, you’ll end up making black tea or oolong tea. In many green tea-producing countries, this is done by pan-frying or even roasting the leaves on a hot surface. In Japan, the leaves are steamed. This gives a completely different flavor profile.</p><p>Where green teas from China might have mellow, nutty, floral, or even toasty notes, Japanese green teas are more vegetal, grassy, and full of umami flavor. Some producers intentionally shade the trees before harvest, which forces them to produce more flavorful compounds. Japanese producers also love to use machines. In fact, the entire process is mechanical. This is in stark contrast to other countries, where you can still find people harvesting and processing by hand.</p><p><strong>Japanese Tea Cultivars</strong></p><p>Now, I mentioned that most tea comes from a single type of tree, but there are many varieties of tea trees worldwide. These are often called cultivars. Think of them as the tea tree equivalent of wine grape varietals. In Japan, there are hundreds of cultivars, and the government has an official registry that recognizes over 130 of them.</p><p>Despite the large number of cultivars, however, most of the green tea in Japan - roughly 75% - comes from a single cultivar called Yabukita. It’s a mainstay known for its high yields, strong umami flavor, and, perhaps most importantly, its ability to be easily processed using machines. Resilience? It’s got that in spades! Yabukita grows in almost every tea-producing region of Japan, with only the warmest and coldest areas of the country limiting its reach. If you ever drink Japanese green tea, there’s a good chance it’s prepared from Yabukita.</p><p>Other cultivars exist with their own special characteristics. Saemidori trees mature early and produce a tea with lower bitterness. Okumidori, in contrast, grows better in colder parts of the country. Gokou is kind of like an umami bomb that is used to produce high-grade matcha and shaded teas. Many other cultivars are used to prepare relatively small amounts of tea.</p><p>The tea that I’m focused on today, though, was mostly forgotten about outside its home region. Instead, it’s a misfit. It was considered unsuitable for large-scale production with a flavor profile that didn’t fit the standard palate of the 20th century. This cultivar is Shizu-7132, and its tea has the flavor of cherry blossoms.</p><p><strong>Shizu-7132</strong></p><p>Back in the 1960s, researchers were trying to find a new cultivar that would supplant Yabukita as the go-to cultivar in tea production. They wanted more umami flavor, stronger aroma, and greater resistance to cold and disease. They didn’t rely on artificial breeding programs, though. Instead, they harvested seeds from Yabukita trees in local tea fields and planted them. Although several interesting varieties were found over the years, many had characteristics that made them less desirable in Japan’s highly mechanical tea production system.</p><p>Shizu-7132 was one of those experimental cultivars. Its strong, cherry blossom-like aroma and flavor were unique, but its leaves also proved problematic during production. Typically, steamed tea leaves are shaped into needles using rolling machines. This step helps break down the leaves and release more flavor compounds. The thicker stems of Shizu-7132 didn’t play well with rolling machines designed for standard cultivars like Yabukita.</p><p>The cultivar does have its mother’s strong resistance to frost and certain diseases, though. Researchers are uncertain what the father plant is. Some even speculate that the father was a foreign variety used to make black tea. This might explain where the “un-Japanese” flavor profile comes from.</p><p>Despite all its positive characteristics, Shizu-7132 was never officially registered. It didn’t fit the mold of what was considered desirable at the time. Sidelined, it was mostly relegated to local tea fields in Shizuoka. We owe its continued existence to the work of local tea farmers in that region.</p><p><strong>What Makes it Special</strong></p><p>Teas made from Shizu-7132 contain coumarin just like fermented cherry blossoms. In fact, the coumarin is produced in a very similar set of reactions during the tea-making process. The cultivar doesn’t just contain higher amounts of coumarin, though. It also contains other chemical compounds that make its tea special. First, Japanese green tea is famous for its <strong>umami</strong> flavor, and Shizu-7132 is no different here. It contains a relatively high amount of free <strong>amino acids, </strong>such as <a target="_blank" href="https://en.wikipedia.org/wiki/Theanine">L-theanine</a> and <a target="_blank" href="https://en.wikipedia.org/wiki/Glutamic_acid">L-glutamic acid</a>, that provide the savory, brothy flavor. They also help to balance the natural sweetness of the cherry blossom flavor and other components of the tea.</p><p>Shizu-7132 also contains relatively higher amounts of compounds that are common in other plants, such as <a target="_blank" href="https://en.wikipedia.org/wiki/Linalool"><strong>linalool</strong></a> and <a target="_blank" href="https://en.wikipedia.org/wiki/Benzyl_acetate"><strong>benzyl acetate</strong></a>. If you’re a fan of lavender or basil, you’ve definitely experienced linalool before. Benzyl acetate, easily found in jasmine flowers, is common in soaps and cosmetics. Both of these compounds contribute distinct floral notes to the tea, giving it a stronger springtime vibe. They won’t make the tea smell like jasmine or a bouquet, but they do add some complexity.</p><p>When combined, all of these compounds make for a unique cup of tea!</p><p><strong>The Taste of a Cup</strong></p><p>Now, anyone who really knows me can tell you how much I love tea and particularly Japanese green tea. I had heard about this sakura-like tea variety in the past, but it’s not something you’re going to find available in the United States or even in some tea shops in Japan. The tea is just not that common! This year, though, I had the chance to buy some directly from a Japanese tea maker. I quickly snagged one before it sold out. This tea is probably one of the most expensive I’ve bought ever, but the excitement of trying an unusual tea was too difficult to resist.</p><p>Japanese-style brewing is rather different than standard Western-style brewing. The leaf-to-water ratio is much higher, and the water temperatures are much lower. Shorter, multiple infusions are the norm. The goal is to extract the savory, umami-rich flavor and sweet notes with minimal bitterness.</p><p>For the tea I bought, I placed 5 g of leaves in a teapot and poured in 150 mL of water at 150 ℉ (that’s around 65 ℃). After one minute, I poured the tea into a cup. This first steeping was a little on the astringent side, but it wasn’t bitter. The cherry blossom flavor was present but on the light side. Overall, the tea was smooth and a bit mild.</p><p>The second steeping is where the sakura notes begin to shine. Usually, the second steeping is more intense than the first. The leaves are fully hydrated, and extraction can occur even in a short amount of time. In this case, another 150 mL of water at 150 ℉ didn’t disappoint. Where the first steeping had a lighter, more subtle cherry blossom flavor and aroma, the second was more like a punch in the face. Amazingly, it achieves this without artificial flavors or flower petals. It also has endurance. After four steepings, the sakura flavor is still there.</p><p>Overall, it was a unique tea to drink. It’s not something I would drink every day, but it was enjoyable!</p><p><strong>Closing</strong></p><p>Shizu-7132 is all the more interesting because it comes from a place that traditionally has valued consistency and efficiency. Compared with tea-producing regions around the world, Japanese green tea is definitely more standardized. And yet, here is a tea that is anything but consistent. Today, the consumption of traditional loose-leaf green tea in Japan is declining. As producers adapt and look for new markets outside of the country, atypical teas like Shizu-7132 are getting more attention. At times, it seems like foreigners know more about it than people living in Japan!</p><p>Thanks for joining me today to hear about the interesting history and chemistry of Shizu-7132. If you enjoyed listening to or reading this, please consider sharing it with those you know or subscribing to my Substack for future content. If you want to learn more about the chemistry of tea, feel free to leave a comment and let me know! Thanks for listening!</p><p></p> <br/><br/>This is a public episode. If you would like to discuss this with other subscribers or get access to bonus episodes, visit <a href="https://johnknightphd.substack.com?utm_medium=podcast&utm_campaign=CTA_1">johnknightphd.substack.com</a>
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Chemical Curiosities is an audio companion to John Knight’s Substack, featuring pieces that explore the molecules behind everyday life, with a touch of organic chemistry. From historical pigments and natural dyes to the chemistry of smells, flavors, and unusual phenomena, each episode reveals a small but fascinating piece of the chemical world.
https://johnknightphd.substack.com/ <br/><br/><a href="https://johnknightphd.substack.com?utm_medium=podcast">johnknightphd.substack.com</a>
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