This is some of the fluffiest bread you can  possibly make.

It is beautiful, sweet, soft, and   stale resistant.

So how do you make something so  delightful?

Starch.

It all comes down to starch.

Inside tiny granules of starch are crystalline  and amorphous regions of polysaccharides,   and if you push water deep into those structures  and break them apart, you can get this.

Okay, I'm losing it with bread.

This  is Japanese milk bread.

It is soft,   fluffy and made with a very specific chemical  process in which you heat or scald a portion of   the flour first.

It's also not supposed  to go stale easily because of magic.

Or   chemistry or whatever, but more on that  later.

We're going to put that chemistry   to the test by making three different loaves  under different conditions.

I am so excited   just to eat a ton of delicious bread.

I've  just been looking at this bread for a day.

But before I cut into it, we will first take  a closer look at one of the key bread making   ingredients, flour.

What the heck is in flour?

I  mean, it's a powder that looks incredibly boring,   but there's actually a lot that is happening  in this package.

It's about 10 to 12% proteins,   a small smattering of assorted  polysaccharides and lipids,   and then usually about 70 to 75% starch,  and that is what we care about today.

Starch.

So starch is a polysaccharide.

Poly  meaning many and saccharide meaning sugar.

So this is starch and it's made up of lots  of glucose molecules all strung together.

Starch molecules usually come in two forms,  either amylose, which is a long linear chain,   or amylopectin, which is a branched  molecule.

Amylopectin is typically   a much bigger molecule than amylose  because of all of the linked chains.

Starch is the main way that  plants store energy.

At the end   of photosynthesis a lot of the produced  glucose molecules are stored as starch,   and that starch forms starch granules that vary  in size and shape between plants.

The largest   amounts are often found in seeds, roots  and tubers.

Things like potatoes and yams.

I don't really know what I expected to happen  there.

This is not good.

Do not recommend.

But you'd think with the amount of stored  sugars in a potato, that it would be sweet.

But it's not because all of those glucose  molecules are strung together into starch,   not free as sugar.

But enzymes in our body  called amylases can break the amylose and   amylopectin molecules down to make them sweet  and to free up all that sucrose, glucose.

There are lots of amylases in our saliva, so  if I let this sit in my mouth for a while,   it should eventually start to taste sweet.

I don't recommend it though.

You can also   do this with saltines, but somebody in our  household ate all the saltines and left an   empty box.

So that demo's going to come later.

Anyways, as I mentioned, besides tubers, seeds   often store a lot of starch for developing plants.

So when you grind down wheat seeds to make flour,   a lot of that flour is starch.

If you zoom  in on starch granules, they have really cool   structures.

Starch granules grow from the outside,  adding layers on top of layers, so they end up   having growth rings like a tree.

Fun fact, some  experiments have shown that in cereal plants,   which are unfortunately not Froot Loop trees, but  rather things like wheat, rye, oats, and barley,   the starch granules grow in day-night cycles.

So they grow in the day when there's sunlight   and then they stop at night creating a ring  each time.

So if you keep a cereal plant like   wheat growing in simulated continual daylight, its  starch granules won't have rings.

That's so cool.

Within the granules, there are crystalline  regions with an ordered structure as well   as amorphous.

Within the granules, there  are crystalline regions with an ordered   structure as well as amorphous regions  without.

The crystalline zone is compact.

This is attributed to double helices  forming between amylopectin molecules,   binding them closely together.

The amorphous  regions, on the other hand, are more likely due   to interactions between amylose and amylopectin,  hence they're less ordered configuration.

So here's why this matters.

Starch granules are  typically insoluble in water below 60 degrees   Celsius.

Now you can put them in water and  they will swell up a bit due to the diffusion   and adsorption of water into the amorphous  regions, but if you dry them back out again,   they'll return to their previous form.

But something magical happens above 60   degrees Celsius.

So this is a roux.

It's a  combination of heated wheat flour and fat,   and here I've used butter, that's used in lots  of different cuisines to thicken things like   soups and sauces, and it's also used to make  the very best mac and cheese.

Fight me on that.

If you heat starch like this, it'll start  to swell and form a gel or paste, and this   is an irreversible process.

Even after cooling  down, it's going to remain a gel or paste.

This   happens because water molecules from the fat get  in between the starch molecules, first entering   the amorphous regions that we talked about.

This  pushes the molecules apart and actually transmits   disruptive forces into the crystalline regions  as well, breaking some of the starch molecules   free from the rest of the starch granule.

This turns it all sticky and usefully gloopy.

Now, if the water content is above 60%,  this process is called gelatinization.

If it's below this, it's called melting or also  referred to as a dual transition regime.

Regime?

Regime.

But we have lost   the bread thread.

What does this have to do  with my fluffy bread?

Well, breads like this   have histories in both China and Japan, and they  use heated flour starters to get their textures.

Tangzhong, the Chinese iteration of this, is made  by simmering water, milk, and flour together.

Yudane, which originated in Japan, is made instead  by pouring boiling water over the flour and then   mixing them together and letting it sit before you  make the rest of the bread.

Now, in both cases,   it is not all of the flour, but just a small  portion that is added to the later dough mixture.

By adding these small portions of preheated  starch, the resulting bread should be fluffier   and softer due to the starch gelatinization.

Sure, I could just tell you this, but I could also   explain with bread.

So here comes the delicious  experiment.

I'm going to make the same recipe   at least three ways.

One with no Tangzhong, one  with 6%, and one with 12%.

Why these ratios?

Well,   because I had a recipe and that made the math  easiest.

We're going to do six, which is what the   recipe recommended, and then zero and then double  it, make it 12.

Math.

Then if I'm really crazy,   I only have three loaf pans, but we might make  some other loaves too just to see how it goes.

Doing the roux, or scalding or Yudane,  or Tangzhong process like this before   baking gives that starch time to gelatinize  before you start actually making the bread,   rather than just waiting for it to  happen during the baking process   itself.

The gelatinization process is gradual  and happens as the temperature slowly rises.

For example, in wheat flour, the gelatinization  typically starts around 60 degrees Celsius and   continues until about 85 degrees Celsius.

Doing this process in a controlled fashion   before baking ensures that a greater proportion  of the starch is going to undergo gelatinization   than might just during baking itself,  ensuring a nice softer bread texture.

Now, this technique is used in multiple  different kinds of bread, including milk bread,   but also pane grano arso, or burnt wheat bread  in Italy.

This gelatinization is the same reason   why you boil bagels before cooking them.

That  hot water gelatinizes the starch on the outside   of the bagel, giving it a different texture  to the non-gelatinized starch on the inside.

Just blew your mind didn't I?

Okay, so we're around 160 Fahrenheit.

Elaine, you can put what that is in Celsius on the  screen.

But yeah, we're really thickening up here.

Okay, so this is my 12%.

I'm at a step where I  got to punch it down and roll it out and all that,   but it's the most appealing to look  at and it rose the most.

So I'm kind   of liking it, but it is a little sticky.

Elaine, I think this is just for you because   there's no way that ACS is going to be cool with  this.

This is not a cooking channel.

Oh, shoot.

Now there's a research paper that looks at how  the structure of bread changes as you change the   percentage of Yudane.

As the percentage increased,  so too did the saccharide and water content of the   bread.

However, at the same time, volume and gas  retention went down.

This is likely because the   gelatinization impacts the gluten structure  in the bread, and so it's probably a little   less structurally sound and can't quite  hold up as big of a structure.

However,   a less sturdy bread also means a softer bread.

So let's see.

Now I get to show you the bread   that I made and then I get to try it.

I'm  very, very, very excited about this.

Okay,   so this is the bread just made using non  gelatinized flour.

It looks fine from the   outside.

It does not have a lot of give, but I  also don't want to crush it.

So like bread, bread.

This is the bread made using the recommended  amount of pregelatinized starch.

It's a little   bit softer.

I can feel that, but actually  it looks pretty similar from the outside.

This one, my final one, is the bread that I  made using double the amount of pregelatinized   starch.

Couple things you might notice.

It's got  a valley in it.

I think two things happened.

One,   it might be too soft to support a structure.

Fair,  interesting.

Two, I forgot... Well, I noticed I   had to play with the liquid ratios a little bit  to get this to be something even close to a dough   because just putting in the recommended amount  of milk plus the recommended amount of the   pregelatinized starch, it was too much liquid.

So then I had to add a little bit more flour,   but I think there just might have been  too much liquid.

This was a wet dough.

It's a little dense.

It's got a crumb, but  we got some nice air bubbles in there.

I'd   eat this bread.

I will eat this bread.

Let's  be real.

I'm going to eat all these breads.

Yeah, I think that's a little softer.

Might be   placebo effect.

No, it's a softer bread.

Sad bread number three, oh, it is raw at   the bottom.

Great British Bake Off would yell  at me for this.

It's very soft though.

I wonder   if this guy baked longer would've been  okay.

All right.

This is bread number one.

You toast that, you put some butter and  honey on it.

Oh my god, it's a nice bread.

This is my appropriately pre gelatinized bread.

I  do think it's softer.

I don't know that it's that   much sweeter.

No side by side there is maybe  a little sweetness difference there.

Okay,   I'm bought in.

I like it.

Let's try my sad bread.

That one is so fluffy, so soft.

Can't believe I'm saying this.

I got to do this again, and I got  to do this one and I got to bake   it longer.

The portion of the bread  that is baked is so soft and so nice.

All of them are delicious.

The one I want  to keep eating though is the mutant one.

But there's another special thing about this  bread.

It's not supposed to go stale.

When   bread cools down, the starch molecules inside of  them start to set with water molecules gradually   pushed away from the starch.

The bread becomes  soft and chewy rather than gel-like and this is   a good thing and it's called retrogradation.

But  after it sits for a long time, the retrogradation   continues and the starch fractions reassociate  in different forms and rates creating crystalline   and amorphous zones.

This can affect the texture  of the bread causing it to harden and go stale.

Except that's not quite the case in this  bread.

When that starch pregelatinized in the   Yudane before baking, it becomes more prone to  breakdown during the baking process by amylases   found in the flour.

This means that there are more  sugars present, giving it a sweeter taste, but it   also means that the average length of the starch  molecules becomes shorter.

Since retrogradation   requires starches of a minimum length to  happen, Yudane bread tends to have shorter   chains on average than other bread.

This means  it experiences less retrogradation and staling.

Additionally, in many breads, fat molecules in  the dough interact with the gelatinized molecules,   creating a kind of support structure that  also delays this staling or retrogradation.

More gelatinized molecules in the Tangzhong or  Yudane bread means more opportunities for this   interaction and fresher bread longer.

So through the power of video magic,   we're going to fast-forward a few  days and then see how I feel about   how stale these loaves are then.

Time travel.

Before I get into testing the staleness of bread.

Learning the science of how starch behaves in  the kitchen to make this video has absolutely   changed the way that I think about using starch  in cooking, and I think is going to change the way   that I cook forever.

It has changed the way  that I think about adding starch to sauces,   to thicken them.

It has changed the way that I  think about why if you put mashed potatoes in   the blender, they're going to get all gluey.

Why  when I was boiling beans for dinner last night,   the water was all bubbly and stiff  bubbles that were sticking together.

It has changed how I cook in the last week.

Okay, let's judge bread staleness.

This is   my very scientific poke test.

It's stiff  now.

It's very, there's not a lot of give,   especially around the edges.

We got a stiff  bread.

This is the one with the pregelatinized   starch and there is a noticeable difference.

It is a little stiffer around the edges,   but the center is just much softer.

Oh, our  poor said weirdo loaf.

This doesn't seem fair.

It was raw on the bottom.

I'm sorry loaf of  bread.

Oh, major difference.

This one, stiff   bread on both sides.

This one is still softer.

Much more give in the pre gelatinized bread.

Taste test.

Yeah, I think that's stale.

I'll  eat anything.

I'm the worst person to do this   test.

So yeah, it's a little stale, but it's  fine.

This one is our pre gelatinized bread.

Yeah, it's definitely still softer.

I'd say  it's probably still past its prime as well,   but it's been a week since I baked them.

Had I  only baked one and had I not been specifically   saving them, I probably would've eaten all this  bread by now.

I think it would have remained   not stale within the period of time in which I  would've happily eaten a whole loaf of bread.

Now if you have any kind of bread that goes stale,  you actually can reheat it in the microwave and   that will temporarily cause gelatinization  to occur.

Again, rebonding starch molecules   with water and temporarily creating a softer  texture.

But once it cools back down again,   it's going to be stale.

You can also try  and prevent staling in any bread in how   you store it.

Retrogradation happens faster at  cooler temperatures, so putting your bread in   the fridge is actually going to make it go stale  faster.

But it will not retrograde when frozen.

So   your best bet is to actually put your bread in the  freezer and you just toast it up when you want it.

But no matter how you slice it, and  I will not apologize for this pun,   you got to try some bread with  gelatinized starches.

It is delicious.

Can we also put a disclaimer at some point in  this video that this is a chemistry channel   and not a cooking channel?

You should not  take my advice on how to make this bread.