- Maple syrup is a delicious treat, enjoyed by people all over the world, but have you wondered how it's made?

For thousands of years, people have been harvesting this watery sap of maple trees during early spring and transforming it into something wonderful.

This is all at the beginning of the process that turns the sugary liquid in the xylem of the maple tree into the sticky goodness that we put on pancakes, waffles and even fried chicken.

While the methods of harvesting and processing sap have changed over the centuries, two things have remained consistent.

The time of harvesting and the science driving the transformation of sap into maple syrup.

In this episode of "Compact Science", we'll explore the sweet science behind our favorite breakfast condiment.

(upbeat music) We are very lucky in this region to have maple trees, specifically sugar maples, red maples and black maples.

During the spring, we extract maple sap from these trees and use that to create maple syrup.

Maple syrup was originally made by the Indigenous people of what is now northeastern North America, including parts of Canada and the United States.

To this day, maple sap and syrup is considered good medicine to many Indigenous people, and is even included in traditional ceremonies and stories.

Small scale maple syrup production still utilizes many of the harvesting and processing methods that the Indigenous peoples of North America developed thousands of years ago.

Today in the United States, Vermont is the largest producer of maple syrup, followed by New York and Maine.

(upbeat music) And have you ever seen the Canadian flag?

Maple syrup is so important to Canadians that the maple leaf can be found on their flag, coins and more.

It takes biology, physics and chemistry to explain the process of maple sugaring.

First, let's talk biology.

In the summer, the leaves of these maple trees make food in the form of sugar through the process of photosynthesis.

Instead of eating food like we do, they make their own.

Think of the things a plant needs to survive, water, sunlight and nutrients.

Using these three elements, trees and most other plants make their own food.

This sugar isn't just used for food.

It acts like antifreeze.

Water freezes at zero degrees Celsius, but it has to be a lot colder for the sugary, water-like sap to freeze.

This helps protect the plant.

During the cold winter.

This food is stored in the trunks and the roots of the maple tree before the winter.

Physics is what makes the sap flow.

Towards the end of the winter when the nights are below freezing and the days are above freezing, the freeze thaw cycle causes a change in pressure, which forces the sap to move.

During the day, the warmth of the sun heats up the sap inside the tree.

This causes the sap to rise as warm fluids rise.

At night when the temperature drops, so too does the sap.

Beneath the tree's bark you could find the tree's vascular tissue, parts of the tree that move water and nutrients up and down.

They're kind of like little tubes that run through the trunk.

These are called xylem and phloem Xylem take water and nutrients from the roots to the top of the tree.

This is where we get the sap that we turn into maple syrup.

Phloem goes the opposite way, bringing nutrients from the top to the tree's roots.

In the summer and autumn, these tubes bring the sugar from the leaves to the roots.

This flow is due to a process called capillary action.

Capillary action is when a liquid like sap moves through small spaces like the tiny tubes in the tree structure without the need for any external force.

It's almost like magic, but how do you get the maple sap out of the tree?

We can tap the tree to interrupt and divert the sap.

Toda y, I'm in the sugar bush at Buffalo Niagara Heritage Village with my friend Sara Miller.

Hi, Sara, how's it going?

- Great, how about you?

- Oh, living the dream, living the dream.

Tell me about the sugar bush.

- Here on site we have about 40 different maple trees that we tap every year for our maple season.

- What's so special about these maple trees?

- Maple trees are really cool because their sap has the highest sugar content, which means that we can tap them each year and make maple sugar as well as maple syrup.

- Does tapping the tree harm it at all?

- It does not, over the years, we've developed smaller and smaller tapholes, so that way the tree is not harmed and it heals itself for the next season.

- You just can't tap any maple tree, right?

- You cannot, no.

The maple tree has to be at least 12 inches in diameter, which equates to about 40 years old.

(person gasping) - This baby's older than me.

- Yes.

- Not much, but there it is.

(person laughing) And then you know many trees, they can continue to be tapped for like 100 years, is that right?

- They can, yes.

You can tap a maple tree over and over, and as the tree gets larger, you can add more taps to that tree as well.

- [Sarajane] Super cool, super cool.

(music whooshing) - [Sara Miller] Modern sugar makers tap their trees with tubes that will run tree to tree and often into the sugar house as well, and it makes the collection a lot easier.

- [Sarajane] So really souped up straws, right?

- [Sara Miller] Yes, run either by gravity or a lot of times they're vacuum run as well.

- Got to love modern technology.

It looks like we have a good one here.

That I think it's ready for a tap.

- I think you're right.

So the rule of thumb is you never want to get too close to your old tap marks, so you want to go about a hands width away.

So I have an old tap mark here as well as a tap mark here.

So I think we should be good to tap right about about here.

So we do it a little bit old fashioned here.

We have our old auger and bit here.

- [Sarajane] Okay, you got it?

- Yes, thank you.

So I will line it up with the tree.

Just slide my bucket a little bit.

All right.

And we only want to tap about an inch into the tree.

- Yeah, there's no need to go any deeper 'cause that's where you can get to these xylem.

That's where the business is.

That's where the sap is.

- And as you're tapping, once the bark starts changing color, you know you've reached your spot.

All right, so next I take my tap, with my hooks I'll be able to hook my bucket on and gently tap it into the tree.

(object tapping) All right, that feels secure.

So now we can hang our bucket and cover it with our lid to keep all the bugs and the rain out.

When we collect the sap from the buckets, it is primarily water, so it's clear.

It just has that slight little sugar content to it, so it's sweet to the taste, but you definitely don't want to pour it on your pancakes.

(sirens whirring) - Now let's talk about the physics and chemistry involved in making maple syrup.

When the sap is collected, it typically contains only about 2% sugar.

This means that a lot of water needs to be evaporated in order to concentrate the sugar and turn the sap into syrup.

To do this, the sap is boiled in large pots or pans.

As the water evaporates, the sugar becomes more concentrated and the boiling temperature increases.

This is where the physics comes in.

The water in the sap evaporates into steam while the sugars are left behind.

The longer the sap is boiled, the stronger and more concentrated the maple flavor is.

Today, some syrup producers use the process of reverse osmosis, which separates the water from the sap.

These special machines use pressure to basically push out the water, leaving the sugary syrup behind.

Chemically speaking, the sugar in the sap is mostly sucrose, which is the same type of sugar found in table sugar.

When the sap is boiled, the sucrose molecules break down into glucose and fructose, which are two other types of sugars.

This gives the syrup its characteristic sweet taste.

Don't underestimate how much work goes into a tasty stack of pancakes.

One gallon of maple syrup is made from 40 gallons of maple sap.

On average, a maple tree will make between nine and 13 gallons of sap per season.

So larger producers need a lot of healthy trees year after year.

From capillary action and xylem and phloem, to the physics and chemistry involved in boiling and concentrating the sap, there's a lot of science that goes into this sweet tree.

(upbeat music) Let's take a deeper look into how temperature can make liquids move.

We talked about how this is essential to the collection of maple sap, but here we could see it in action with this experiment.

Here we have a shallow dish of water and a candle.

I'm going to light the candle and then place this dome over the dish.

What do you think will happen?

(lighter clicking) All right, I'm going to put this on top, now flames are hot, what's it doing?

It's heating up all the air inside, but takes a little bit of time.

You'll start to notice something.

Take a look at the water line.

Ah, yes, it's happening.

Oh my goodness.

That is so fun, that's so fun.

Look, the water is rising up the side.

I love this.

It's rising up the sides, but why?

Just as the rising temperatures in the vascular tissues of the maple tree pushed the sap through the tree, here, the reduction in air pressure creates a vacuum, and hence, the water level rises.

So the next time you're upset about the freezing temperatures at the bus stop, remember, it is that without cold weather and some delicious chemical changes, we wouldn't have the delights of maple syrup.

(upbeat music) (object buzzing) We learned how the transformation of maple sap into delicious maple stickiness is a story of temperature dependent physical and chemical changes.

If you're interested in learning more about capillary action, check out our Compact Science Viewer Challenge.

We have a fun and colorful experiment that you can try at home.

I'm Sarajane Gomlak-Green, and you've been watching "Compact Science".

Until next time, stay curious.

(upbeat music) - [Narrator] Compact science is funded in part by the Joy Family Foundation and by the New York State Education Department.

- Today I'm in the sugar bus.

What, what?

I can't say words today, well, any day.

- You could probably fill this bucket within about eight hours.

- Okay, all right, well, I'll hang out here and I'll wait for it, so I'll let you know.

This means that a lot of water needs to be evaporated in order to concentrate the sugar and to concentrate, concentrate the, to concentrate.