Cucumbers zucchini

Hey, why aren't cucumbers zucchini? I mean,

They look like the exact same thing.

They just taste kind of different.

I mean, really different, actually. And why do I like cucumbers so much, even though they just kind of taste like water, or do they? Why are cucumbers covered in tiny spikes? Are cucumbers actually cool in temperature or is that just a figure of speech? Does some cucumber varieties really make you burp? And of course the most pressing question of all, why do some cucumber varieties explode? This is real.

They're called squirting cucumbers. The jokes write themselves. But first things first. Why is it that cucumber is not a zucchini or some other kind of squash? Well, simply, it's because cucumbers and squash aren't that closely related. I mean, they are related, but cucumbers are much more closely related to melons, certain kinds of melons.

Indeed, you could call cucumber a kind of melon if you wanted to. I mean, melon is not a scientific term. It means whatever we say it means. Cucumber and cantaloupe here are both members of the genus Cucumis — they're botanical siblings. Like other melons, cucumber is a berry that grows from the ovary at the base of a flower as all fruits do. Probably the only reason we consider it a vegetable and not a fruit is that its sugar content is pretty low, plus we usually eat it when it's green and unripe. Leave it on the vine too long and it turns yellow, like lots of melons do. I'm calling cucumber a melon.

If that seems weird to you, look at this cucumber I grew in the garden. Look at that spot of skin that's starting to dry. Under the microscope, looks like cantaloupe skin, doesn't it? Like other melons in the genus Cucumis, cucumbers are climbers. They climb up and grab a hold of structures with these little tendrils. Tendrils are these awesome twisting arms that reach around any hard surface they encounter, due to an asymmetric contraction of a ribbon of fiber inside them. The tendrils pull the vine up toward the nourishing light. Squash, like this zucchini I'm growing, these are vines too, and they're from the same family as the cucumber, Cucurbitaceae, but cucumbers are more closely related to some melons. And like melons, cucumbers have an unusually high water content, about 96% water this guy is, and that's a solid adaptation because cucumbers are from India.

All members of the Cucumis genus are from very, very hot places where water is precious. One function of the store of water is probably to help get the baby seeds in here growing, even in very parched conditions. This very high water content leads to the perception that cucumbers are just crunchy water with no higher purpose than to be a substrate for dressing. True, they're not super nutritious. They have some vitamin K, fiber, that's about it. But like other melons, cucumber does have a distinct flavor. If you really want to taste it, make cucumber water, one of my favorite things. Steep some cucumber slices in cold water for at least an hour.

This I left sitting overnight and wow, with nothing there to compete, I can really taste it, plain as day. Cucumber aldehyde. What is cucumber aldehyde? It's this.

I have it in a little bottle

At a 0.1% solution, highly diluted, and yet even still i can smell it without even opening up the lid.

Just because it's highly diluted in cucumbers doesn't mean it's a weak flavor. It is not a weak flavor. Our friend Harry Sherwood sent this to me — London perfumer and PhD candidate in philosophy of perception. Cucumber aldehyde.

It's an aldehyde because it contains this oxidized alcohol group down here. "And it's just the most cucumbery part of cucumber. It's just so cute. And wet. And cold, somehow." . Yeah. We'll get to the cold thing in just a minute. This cucumber aldehyde is also found in watermelon because cucumbers are melons.

It's also found in bread crust. If you've ever thought that there was kind of a bready note to cucumbers, you weren't making that up. So it tastes oily and green and cool, but that might just be an association that we have. It's not anything chemesthetic going on. Menthol in peppermint and the capsaicin in chilies, they actually stimulate our temperature sensors. That's chemesthesis. If there's something like that going on in cucumber, scientists have yet to put their finger on it.

Here's a 2021 paper out of Malaysia where they put different combinations of stuff on people's skin and ask them to rate how cooling it felt. The winner was a combination of peppermint oil, cucumber extract, and aloe vera, but the authors here don't offer any chemical explanation for cucumbers' inclusion. Nonetheless, East and South Asian cultures associate cucumber with coolness much in the same way that we do in the west. In English, we have an expression, "cool as a cucumber.". One explanation could simply be water. Water has an extremely high specific heat capacity, meaning it takes a lot of energy to make it warmer. Plus it's pretty conductive. So if water is cooler than you, you feel the heat of your body conducting away into the water.

That's cooling. Since cucumber and other melons are simply wetter than most other solid foods we eat, this may be why they feel cool to us. There is a common unsourced claim on the internet that cucumbers are often cooler inside than the ambient temperatures around them. I've had this at room temperature for a while and let's just take its temperature. And inside, it is, well, it's room temperature, but imagine how cool it would be if we had kept this in the fridge. It'd be cool, and it would stay cool for longer than other foods because of all of the water with its high specific heat capacity. The soothing sensation of cucumber is counteracted somewhat by the spikes on the surface. Really quite sharp and hard, must be removed before eating.

These spikes are trichomes, according to this 2018 paper out of China. They're much more prominent on baby cucumbers like this little guy. The trichomes rise out of epidermal cells, skin cells, and they're quite soft at this stage. But as the fruit matures, the trichomes dry out and harden. You can see this one under the microscope is still a little green and soft, but eventually they all look like this, super dry and hard and sharp. In some cucumber varieties, the trichome has a glandular function. They excrete elements of a protective cuticle for the cucumbers surface, but all trichomes probably function as structural protection. They're just big spikes that keep away insects and other animals who would eat the fruit.

If you have no idea what spikes I'm talking about, that's probably because you've only ever seen these at the grocery store, cucumbers that have been washed and effectively polished to break off those little trichomes.

The problem with washing all kinds of

Fruits is that it blasts away the natural waxy coating that fruits have to protect themselves from drying out.

So processors have to replace that with actual wax, beeswax, maybe even petroleum wax. This guy from the store has definitely been waxed. Every food safety authority says these waxes are safe, just kind of gross, but they're assuming you're going to peal this at least a little bit. The skin on this typical American variety is quite thick to bite through. Not so on this so-called English cucumber. This has a thin skin.

You really don't have to peel, which is why the processors wrap it in plastic instead of waxing it. You can just roll the plastic off and eat it. The seeds inside are also smaller and less noticeable. So these varieties are often marketed as being seedless. Many of these slender seedless varieties from Europe and Asia are often marketed as being burpless. That's an unappealing word. What do they mean by burpless? Well, some people seem to get stomach irritation from cucumbers, and sometimes this manifests as gas buildup in the upper digestive system and belching to release it. Commonly, this is attributed to bitter compounds in cucumbers known as cucurbitacins.

Cucurbitacins are definitely real. They are definitely bitter, most concentrated in the endocarp right around the seeds. But do they really make you burp? So far, the only person who seems to have systematically investigated this burning question is Dr. Todd C. Wehner at North Carolina State University. Very small study. He recruited six judges to eat lots of different cucumbers across two growing seasons and to record their burps. Those judges who'd never had this problem in their lives before reported no excess burping.

Those judges who have noticed this problem before did report more burping when they ate standard American varieties, as opposed to the burpless Asian varieties. But the findings also cast doubt on the notion that cucurbitacins are to blame. No one really knows what causes the cucumber burps. We know a bit more about what causes cucumber explosions. I give you Ecballium elaterium, the squirting cucumber of Eurasia. Nobody eats this. The cucurbitacins are so concentrated here that it's incredibly bitter and indeed toxic to eat, but who wants to eat it when you can watch it for entertainment? This is some awesome old BBC nature footage that I licensed. When the fruit is ripe, a huge amount of osmotic pressure builds up inside.

A thin wall of tissue breaks. The fruit drops from the stem, and the seeds come squirting out. It obviously evolved as a means of seed dispersal, and it's apparently quite effective. This is regarded as an invasive weed, real gushers. It's a shame we can't eat those, but we can eat other small varieties of cucumber. And that's good because they're useful for pickles. Pickling cucumbers are usually small and have an even roundness, an even thickness around them that makes them pickle at all the same rate. These small ones do tend to be bitter, lots of cucurbitacins, but that's not such a problem with pickling.

Xinyue Fan explained why in her 2021 master's thesis at North Carolina State. She did some awesome experiments and proved those bitter cucurbitacins are majorly reduced by fermentation and acidification. She speculates those bitter compounds might get metabolized into other things. They might also simply get drawn out into the brine and diluted, but regardless, that's why you can make pickles with little bitter cucumbers. And I am grateful for that, because pickling cucumbers have given us kosher dills, quite possibly the greatest single contribution of New York Jewish cuisine. And that's really saying something, but how these are made, we'll have to investigate another day. In the meantime, go eat a fresh melon because you know, it's a melon. Even the over rip yellow ones can be nice, as long as they're not too bitter. Check out the pretty color inside. Tastes a little sour, but I mean, it's a fruit, it's a melon, it's a cucumber...