- [Rob] Are you feeling curious?

- Yeah.

- Today on Curious Crew, keep your eyes peeled, we're exploring fruit science.

It's turning into cottage cheese.

You're gonna eat up this tasty episode.

Squeeze the day.

- [Narrator] Support for Curious Crew is provided by MSU Federal Credit Union.

From sweet peas to teens, MSUFCU offers you accounts that grow with children.

With financial education, gaming apps and events, MSUFSU provides the tools and resources to make learning about finances, fun and interactive.

Also by the Consumers Energy Foundation, dedicated to ensuring Michigan residents have access to world class educational resources.

More information is available at consumersenergy.com/foundation.

Consumers Energy Foundation, supporting education and building sustainable communities in Michigan's hometowns, and by viewers like you.

Thank you.

(upbeat music) (pencil scribbling) - Hi, I'm Rob Stevenson and this is?

- Curious Crew.

- Welcome to this show, everybody.

We always like to start every episode with a couple of discrepant events because discrepant events stimulate?

- Curiosity.

- That's exactly right.

And I've got some fun ones for you today.

You might have noticed on my table, I've got this glorious fruit bowl because I'm going to be making a fruit salad.

But before I do that, I think I need a little mood lighting.

So I've got a grapefruit right here.

(upbeat music) Ahh, now, I was thinking about this mandarin orange, and I'm gonna peel this, but I have a wondering for you as I peel this thing.

How many of you have played with water balloons before, my friends?

Of course.

Now, I've got a whole tank of water balloons here, except these water balloons only have air in them.

Now Rishabh, I've got a wondering for you.

I've got some mandarin orange rind right here.

What do you think might happen if I were to squeeze this rind over a water balloon?

- Would it pop?

- I don't know, (chuckling) but just to be on the safe side, safety first as always, I think we should give this a whirl.

Let's see what happens.

(balloons popping) - Oh.

Oh yes.

It's rind blowing.

Now, I've got another wondering for you.

Tauren, what might happen if I put this Mandarin orange inside a glass of water?

- Will it float?

- Let's find out.

Let's put it in there.

Aww, it floats.

Okay.

Now, how about the peeled Mandarin orange and another glass of water?

Tauren, What's gonna happen here?

- Maybe it'll sink.

- I always find this discrepant event especially appealing.

(drums) Ready?

Oh, it not only sink, it got wedged down in the cup.

That's gonna be fun to get out later.

Okay, now we've got some interesting discrepant events going on here and I'm gonna invite three of you to do a little scientific modeling to see if you can figure out how these things work, using evidence throughout the show to see if you can come up with an explanation.

Who wants to engage in a little modeling moment?

What do you guys think, who wants to try this?

Okay, Kah'reice, Carmela, Janellyn, you guys are gonna do this.

Now does somebody have a guess what we're gonna be talking about in this episode?

What do you think we're gonna be investigating today?

Ian, what do you think?

- Are we talking about oranges?

- (laughing) Even more than just oranges, we're gonna talk about fruit, fruit science.

It's going to be a fruit fiesta.

You're gonna wanna stick around, this episode is berry interesting.

(upbeat music) - Okay, let's see if we can figure this out.

- I know that there's citric acid in fruits, I wonder if that's what causes them to pop.

- That could be, but the rind also has something to do with keeping the orange afloat.

- Yeah, you know, the floating oranges reminded me of bobbing for apples.

Do you think if we removed the skin of the apples that they would sink?

(upbeat music) - [Rob] Having a fruit salad is a wonderful treat and we often put many kinds of fruit in them, but did you know that there are around 2,000 different kinds of fruit around the world?

Now, that fruit salad may be too big.

Scientists describe fruit as the plant part that has seeds, but there are a lot of differences.

Some are soft, juicy, and sweet, while others have harder shells and some are not even safe to eat.

You may even be surprised to know that things like tomatoes, peppers, pumpkins, cucumbers, and even green beans are technically fruits.

Fabulously fun fruit facts.

So, you know, when we think about fruit, there's actually a lot of chemistry involved in fruit.

And we're going to do a little investigation right now with lemons and pennies.

And first of all, Tauren, what happens to pennies once they start getting old?

- I think they start getting dull and lose their shine.

- So they get that tarnish on there.

Now, that is actually a chemical reaction.

Copper, when it's exposed to oxygen in the air, actually develops what's called copper oxide, which is a molecule that covers the top of the copper.

And that actually makes it really, really dull.

Now, we have been starting an investigation about 15 minutes ago, and we took some pennies, some tarnished pennies, kind of like the ones I have here on my plate, and we cut a little slit in the top of the lemon and pressed a tarnished penny inside.

We've left it there for about 15 minutes now.

Now, Rishabh, will you be kind enough to pull yours out and tell me, what does your penny look like now?

- So the part of the penny that I put in the lemon is now all shiny.

- Oh my gosh, it really is shiny.

Okay, I'm gonna pull mine out too.

Tauren, you can pull yours out too, see if you get that sort of result.

Oh yeah, mine's getting shinier too.

Oh wow, Tauren, yours is really shiny, oh my gosh.

Now, the amazing thing is something inside the lemon is removing that copper oxide.

So Tauren, do you have a guess what might be causing this change in the penny?

- Is it the citric acid?

- (bell dinging) That is exactly what it is.

The citric acid in the lemon is actually really good at dissolving copper oxide.

And so we can get rid of that top dull layer on the penny and all of a sudden we have a nice shiny penny again.

So, that's one way you can clean your pennies.

Now, there's something else I wanna show you about lemons and citric acid, and it has to do with what I've got on this plate over here.

I can do this with limes too.

The first thing you might notice is Dr.

Rob, you have a lot of things sticking out of those lemons.

So, I've got a little piece of copper stuck into this lemon, which goes over to a piece of zinc in the lemon behind it.

Then it goes again from copper to zinc copper, copper to zinc, so they're all connected.

Now, I have yet to connect these last two, but watch what happens when I put a piece of copper in this lemon and a piece of zinc in our final lemon.

We are going to see if we can convert chemical energy into electrical energy.

We start getting a reaction on the clock right there.

As soon as we put those probes inside, we start having electrons moving from the copper through the acid to the zinc.

So we actually are converting chemical energy into electrical energy.

Amazing.

I could almost say that's rather sublime fruit science.

You gotta love it.

When you think of fruits, citrus may be the ones that come to mind, but there are over 100 different kinds.

Most fruit that we eat are hybrids of the pomelo, mandarin orange, and citron, but citrus fruits do have other similarities.

They often have juicy segments, a flavorful zesty rind that surrounds them, and have a weak acid called citrus acid that helps preserve the fruit.

The fruit flavors differ though ranging from a dry flavorless citron to a sweet orange, to a bitter lemon or lime due to the greater amounts of citric acid.

Wow, that's sour.

So, if we're talking about fruit science, we have to talk about enzymes.

So Ian, what are enzymes?

- Aren't they things that speed up chemical reactions?

- That's exactly right, in living things, they can either bond molecules faster or break 'em apart faster.

Excellent.

Now, in fruits and in other living things, there is an enzyme called catalase, and catalase is a really powerful enzyme that can break down peroxides, turning it into water and oxygen.

Now, on my tray here, I actually have five little cups with hydrogen peroxide inside, so I wanna know which of these fruits has more catalase.

Now, Carmela, if a fruit has more catalase, what might happen when I put it into the peroxide?

- I think there's gonna be a really big reaction and a lot of bubbles are gonna appear.

- That's exactly right, 'cause it's gonna give off the product of oxygen.

Good job.

So, we're gonna try this, we're gonna drop each one in and see what happens.

I'm gonna take this little piece of avocado, this little piece of banana, the apple over here, some melon, it's actually a little cantaloupe, yum.

And some pineapple, we'll drop this in here.

Now, we'll come back and take a look at this again in just a moment, so it has some time to react.

Now, you also have started an experiment at home.

Carmela, can you tell us a little bit about the experiment you started?

- We cut one apple in half and covered one half of the apple with sugar and then left the other half blank.

- And what are you noticing when you look at those two halves of the apple now?

- The half that I put sugar on looks a lot more normal, but the other half is starting to get browner.

- Interesting.

Okay, and Ian, did you see something similar or do you have a different result?

- Yeah, it's the same thing for me.

My normal apple is brown like an apple would look like, but my sugary one, it looks perfectly fine as if nothing had changed.

- Now this whole browning effect is really interesting.

This is another enzyme actually, it's called PPO, it's got a really long name.

And when we combine it with other compounds in a fruit, when those get exposed to the oxygen and air, it starts forming a chemical reaction, forming melanin, which is the same pigment as in your skin, your hair, your eyes.

Now, we've seen how bananas brown really easily, you've seen how fruit when it gets damaged, bruises, or when we leave fruit cut on a plate, it starts to brown.

Now, I have four plates here, on one plate, all I did was cut the pieces and just left them there.

We're calling that the control.

And if you look at it, the banana has really started to turn, the apple is starting to turn brown.

The next two as I move towards me, the sugar and water, I covered both, one in sugar, one in water.

You're noticing what that does.

It's trying to slow down that reaction by minimizing how much oxygen can interact with those compounds and that enzyme.

But finally, if you want a great trick, check out the lemon juice, the lemon juice slows it down a lot.

It changes the pH of the enzyme and it can't work as well.

Now let's look back at this catalase over here.

Carmela was talking about bubbles, and in fact, there's one that really stands out as pretty bubbly.

That one is the avocado.

The avocado has a lot of catalese and banana would probably be coming in second.

The one that has the least amount is probably going to be the apple.

Enzymes are in all kinds of fruits.

Now you guys, you know the best way to make sure you prevent your fruit from browning?

Eat it when it's fresh.

Here are some tricks to make some fruits ripen faster or last longer.

To ripen avocados faster, wrap it in newspaper and place it in a brown bag with a banana.

This tip can speed up the ripening by five days.

Wanna keep the flavor of your tomatoes?

Try sTaureng them on a counter.

Yum.

Citrus fruits on the counter and kept out the sun will make them last longer.

Plus, they're beautiful to look at.

Bell peppers will stay crispier if stored in a paper bag.

And if you put foil or plastic wrap around the banana stems, the skin won't brown as fast.

Those tricks are pearfect.

(upbeat music) So, don't rocks rock you guys?

- Yeah!

- But we can't take 'em for granite.

Sorry.

(drums) - In the rocks episode, we took little bits of different colored crayon pieces.

- We're actually going to make a wax model of different kinds of rocks.

- Which represented the sediments of the rock cycle.

- So, what do we need to make sedimentary rock?

Ambrose, what do we need?

You need rock sediments and pressure.

That's exactly what we need.

- And put them in a syringe and layered the colors, and then we stuck the syringe down and pressed them together.

When we pulled it out, it was like a sedimentary rock.

- That was extreme pressure.

- I wasn't sure if the crayon pieces would stick together all that well, but it turned out really cool.

(upbeat music) - STEM challenge.

So, orange you having fun learning about fruit science today my friends?

- Yeah.

- So, we've got a fun STEM challenge for you.

The kids have been really hard at work, getting ready for this investigation.

In fact, what they had to do is they had to peel an orange, take the rind and then soak it in vinegar for two weeks in the refrigerator.

So, I know you guys have done that and they're now ready to continue their build.

They are making orange concentrated cleaner, and I think they're even going to dilute it.

Are you guys ready to start?

- Yeah.

- All right, let's do it.

(upbeat music) - There's lots of bubbles in the bottom of the bottle.

- Oh no, I spilled.

- I find it extremely fascinating that there could be chemicals in the orange that make it a cleaning solution.

- It smells good.

One thing that I noticed in this experiment was the very prominent smell of the cleaner.

- Now my hands smell like orange and all citrusy.

- Now, the spray is done.

- Oh cool.

(laughs) I thought it was really cool that I could create my own cleaner out of fruit and it was super fun.

- My table looks so much cleaner now.

- It works pretty well to be honest.

Whoa, my table's dirty.

- So you're all scrubbing.

You must be ready to report out.

So how's the cleaner working?

- Terrific.

- So I gotta let you in on the secret here, when we were soaking those orange peels, we were actually extracting limonene oil right out of the rind of the orange peel itself.

Now, limonene is a great oil that is actually a solvent.

Now, if you mix that with vinegar, which is already a good cleaner, you not only have a good solvent, but a good degreaser.

And I bet you notice the smell.

Did you guys like that?

- Yeah.

- Now, limonene gives that orange smell.

Interestingly, limonene also makes a lemony smell.

It all depends on what sort of compounds that you have there.

So, here we have a couple of other eco-friendly cleaners, one that you can use after getting your hands all greasy, working on a car, and this one that can polish lots of different surfaces.

But you, you made your own just with vinegar and limomene from oranges.

Not only can you have a clean space, but it smells terrific too.

We had great success making a fragrant cleaner with orange peels and vinegar.

You can also make a furniture polish out of lemons.

Just combine two parts vinegar, two parts olive oil, and one part fresh squeezed lemon juice.

A small amount will be plenty.

Now dip a clean rag in the solution and wipe it with the grain of the wood.

After a moment, wipe the same direction with a dry cloth soaking up the leftover cleaner.

Look at that, polished wood and a lemony scent.

So, one of my favorite things to do with good fruit is to make a fruit gelatin cup.

It's so much fun.

You can take hot water and sugar and gelatin and mix it with cold water.

And as it starts to chill, you can fold in some fruit.

You guys enjoy gelatin fruit cups?

- Yes.

- Yeah.

- What's your favorite flavor, Janellyn?

- I love pears in gelatin.

- Oh, that's awesome.

And how about you, Kah'riese?

- I'm more of a peach person.

- That's awesome.

So let me explain a little bit more about gelatin.

You know how gelatin is really jiggly and firm?

We need to understand why that happens.

Picture a plate of wet spaghetti noodles, okay.

This tangled mass of spaghetti noodles.

Now, collagen proteins work the same way, that gelatin, those proteins.

they get all tangled up and there's all these little pockets in it.

In those pockets, we can capture sugar and flavor and fruit and as it all sets up, all of that is held together.

Now, I've made some fruit cups here myself, but something's really unusual.

Kah'Riece, I wanna point out this one over here with the pineapple and I'm gonna give it a little shake and I want you to tell me, what are you noticing?

- It's a lot more watery than a normal jello.

- This one you could like drink.

And look at this one with the Kiwi.

Notice this one too.

But if I go to the other end where I've got some blueberry, notice, we've got a really great gelatin.

You might be thinking, okay, why did some of them set up, and these two over here did not?

Well, it has to do with an enzyme that's in these two fruits.

There's an enzyme called protease, and what happens is it actually acts like scissors and cuts those spaghetti noodles, those long collagen proteins.

It cuts them and cuts them and cuts them.

And you know what?

They're too short to firm anything up.

So, here's a trick, if you ever want to make your own gelatin cup, there's a few fruits to be careful of.

Pineapple is one, kiwi's another, mango, papaya, guava, fig, all of those have these protease enzyme, which will ruin your gelatin cup.

Now, there's something else I wanna show you, which is really interesting.

I've used the same protease enzyme from pineapple juice.

This is a container of milk and I've added just one teaspoon of pineapple juice.

And if you look closely, you might notice that that doesn't really look like milk anymore.

It's already starting to separate.

The protease enzyme in the pineapple juice is actually disrupting the emulsion of the milk and separating the casing out of what's called the mycels.

And you know what it's doing?

It's turning into cottage cheese.

Who knew pineapple juice could actually turn milk into cottage cheese?

Most people enjoy fresh fruit, but dried fruit is a great snack too.

Choose the fruits you'd like to include such as pineapples, bananas, apples, pears, peaches, plums, strawberries, mangoes, or berries.

First, peel the washed fruit, remove the seeds and cut them into thin slices.

You can either dunk them in lemon juice or sprinkle them with sugar.

Lay them on a baking pan with parchment and heat them in a 200 degree oven for three to five hours until the edges dry and they begin to shrivel.

Let them cool on rack and enjoy.

Yum.

That's one in a melon.

(upbeat music) (pencil scribbling) - Are you curious about careers in science?

Hi, I'm Genesis, and today I'm here with Nadia Berenstein.

Hi, Nadia, can you tell me where you are and what you do?

- Hi, Genesis.

I am in Brooklyn, New York, and I am a flavor historian.

- How is STEM involved in what you do?

- Well, technically I am a historian of science and I got interested in food and flavor really by studying the history of the science behind the ways that the food that we eat tastes the way that it does, and specifically the history of artificial flavors.

- What's your favorite flavor to research and why?

- Some of my favorite flavors to study are some of the earliest artificial flavors that you can still taste in the candy and soda pop that we consume today.

- Nadia Berenstein gave me a lot of food for thought when it comes to flavor history.

Explore your possibilities.

(upbeat music) (pencil scribbling) And now, back to Curious Crew.

(upbeat music) - So we know that some fruits have different enzymes or citric acid.

I've been thinking about the popping balloons in the STEM challenge.

- Me too.

The orange cleaner was a good solvent.

- Yeah, exactly.

And the natural oils from the rinds that Dr.

Rob squeezed might have been what caused the balloons to pop.

- So have you guys had fun learning about fruit science today?

- Yeah.

- Awesome.

Now it's time to return to these discrepant events to see if we can make sense of 'em.

And I know three of you have been having some fruitful discussion.

So, what have you guys figured out about the sinking citrus, Kah'Reice?

- We think that there might be air in the rind of the fruit, so after you peel it, it'll sink.

- The interesting thing about fruit and the skin, or the rind on top of that fruit, there's air pockets in there and this orange is a really good example, 'cause this is a really thick rind.

And so there's going to be a lot of air pockets making it really really porous.

Now, when we have the peel on, it adds to total mass.

This total mass, if we place it in water is actually less dense than water and so it's going to float.

As soon as we remove that peel though, we've removed some mass, we've removed those air pockets, and now this volume of fruit is actually gonna be more dense than the water.

Should we put it in one more time, you guys?

- Yeah.

- All right, keep your eyes peeled.

Here we go.

Oh yeah.

Wedged one more time.

Excellent.

So Carmela, what do we know about these popping balloons?

- Well, we think that when you squeeze the rind, the natural oil pops the balloon.

- Yeah, and because we know that limomene is a good solvent, it probably weakens the latex of the balloons, which makes them pop.

- Excellent.

So, we do know that limonene, as you mentioned, is a great solvent, and you're exactly right, it does weaken the latex of the balloon.

Now, you'll notice I chose water balloons, 'cause water balloons are already really thin.

I didn't use party balloons.

Should I try it one more time though?

Okay, as the old adage says, right, squeeze the day.

Let's see if we can have any sort of reaction on these balloons.

Isn't that amazing?

So now, if we did this same activity with a party balloon, I can take this off because I'm really not going to have much of an effect.

Party balloons, the latex is so thick, because the polymers are crosslinked, so this actually won't do anything.

Did any of you think it might have been the citric acid popping the balloons at first?

I thought so.

I thought so.

Now, if I have some citrus acid from this lemon juice and I put some right on a party balloon, it doesn't really do anything.

Now, if I have concentrated limonene and I put it on here, even a party balloon's gonna get popped.

One more thing I wanna show you.

That is our grapefruit candle.

You're probably wondering how I did that.

This is actually the other half of the grapefruit.

I cut it right around the center and I separated the two being careful to leave the stalk inside.

Then, by adding a little bit of olive oil in there, that stalk acts like a wick and it will draw the oil up, and you can actually light it as a candle.

You might wanna put it on a tile plate or something like this, 'cause it can get hot.

Isn't that interesting, you guys?

- Yeah.

Well, it looks like I can get back to my fruit salad.

Yummy, yummy.

So, remember my friends.

- Stay curious.

- And keep experimenting.

Get your curiosity guide and see more programs at wkar.org.

- [Narrator] Support for Curious Crew is provided by MSU Federal Credit Union.

From sweet peace to teens, MSU FCU offers you accounts that grow with children.

With financial education, gaming apps and events, MSU FCU provides the tools and resources to make learning about finances, fun and interactive.

Also by the Consumer's Energy Foundation, dedicated to ensuring Michigan residents have access to world class educational resources.

More information is available at consumersenergy.com/foundation.

Consumers Energy Foundation, supporting education and building sustainable communities in Michigan's hometowns, and by viewers like you.

Thank you.

- I might have some fruit references throughout our dialogue today.

This episode is berry interesting.

Orange you having fun learning about fruit science today, my friends?

Keep your eyes peeled.

Here we go.

This crew is one in a melon.

(laughing)