Okay.
In this video, I'm going to show you why the "Tangzhong method as you know it" sucks, well, sort of. I'm talking about the popular Tangzhong method with the ratio of one part flour to five parts water that is commonly shared online because I think, one, it’s actually confusing
something that's very simple. And two, it has some serious limitations
that result in you not being able to get the full benefit from the method,
as you'll see later. It's actually crazy how popular
this particular Tangzhong method has become, despite having no solid basis
for the ratio used. So to explain this, you need to know
that Tangzhong and the alternative that it's frequently compared to Youdane
are in essence the same thing. Yudane and Tangzhong
are simply the same characters pronounced differently in different languages
in Chinese, Tangzhong, and in Japanese, Yudane. But in English recipes Yudane is popularly used to refer to a water roux starter made with one part flour
to one part boiling water and Tangzhong commonly means a water roux
starter made in a pan with one part flour
to five parts of water. The difference in the ratio and the way
Yudane and Tangzhong are prepared, have led many to believe
that they are totally different. The thing is, in its country of origin,
Japan, Yudane has no such strict convention of
being one part flour to one part water. Yudane is simply refers
to the mixture of flour and water heated to produce gelatinous starch
with a variety of ratios. Take a look at this paper
published in 2015. This section on the preparation of heat
treated wheat starch. It is reported that Yudane is generally prepared by mixing equal amounts
of wheat flour and hot water. However, there is no clear definition
of the ratio of wheat flour to hot water. And in fact various types of Yudane are produced with various mixing ratios. This paper then cites two patents and another paper
as references to support that statement. One of the patents actually goes
as far back as 1999. In this patent,
Yudane is made with 100 grams of flour to 80 to 120 grams of water. Other patents or references
mention different ratios. The paper then continues on to state
that for practical purposes, the Yudane they’re using is to be made
with the ratio of one part flour to two parts water ratio of 1 to 2. An important fact to glean
is that obviously we can raise the amount of water
so as to make it easier for us to prepare Yudane. So technically, even the popular Tangzhong
with it's 1 to 5 flour to water ratio can be considered as simply
another variation of Yudane. We'll get to the science behind this. But first, let's move to Taiwan,
where the kanji characters pronounce Yudane in
Japan are now enunciated as Tangzhong. The TangZhong method with it's 1 to 5
flour to water ratio was said to have been spread outside of Japan and Taiwan
by a book written by Yvonne Chen. Interestingly,
I found a very comprehensive master's thesis on Tangzhong written by Keyuwen published in 2004, a year before the recipe book
written by Yvonne Chen was published in the section on the definition
and the origin of Tangzhong, the paper starts by stating the word TangZhong is from the Japanese word Yudane
and the Okamoto Flour Milling Company of Japan is quoted
as the first company in Japan to publicly use this method,
citing a few references published in 2002. So Tang Zhong is Yudane. I've mentioned this before
in my previous video on this topic in the book by Yvonne Chen,
she also mentions the origin of Tang Zhong is Japan. So there is no doubt
about the origin of this method. The 1 to 5 ratio,
the book introduces is the issue here. That's a lot of water. There has to be a good reason
for it. Right. But I've looked under the oceans
and over the mountains. Not only have I not found out
where the number comes from, I have actually found enough reasons
to believe that it's a bad idea. So let's start with the last one. Why is it a bad idea? Many research papers on Yudane
or Tangzhong prepare the water roux starter with the flour
used for the water route in the range of 10 to 50% of the total flour
used in the recipes. Obviously, based on Baker's percentage. Researchers then subject the water roux starter, the doughs, and the final breads to a range of tests using Farinograph, Extensograph, Texture analyzer,
colorimeter and also Scanning electron microscope, SEM. From this research, we've learned
that Yudane or Tangzhong is best made with the flour content
less than 30% of the total flour, and 10% is considered
to be the bottom limit. At one time it was actually made
in the range of 5 to 50%. Higher percentages may slightly compromise
the appearance and volume of the breads, but substantially enhances the flavor,
softness and the shelf life of the breads. So it is natural for home
bakers like us to want to try experimenting within that range. So far, most of the Tangzhong bread
I've made have used amounts of flour in the range of 5 to 8% of total flour
weight. It's not like they have no effect. It's more like it's not enough Tangzhong. So, lately
I've pushed my limits to 20% and I've found it to be superior
in taste, softness and flavor. But the bread does suffer a little
when it comes to height and volume, which I'm working on fixing videos
coming up when I'm done with research. But for now, let's address
the immediate problem we face If we try to do this with the common Tangzhong method, how exactly are we going to use 20% of the total flour to make Tangzhong
using a 1 to 5 flour to water ratio? Multiply 20% by five,
we get 100% water hydration! Wow,
we've just hit an extreme level of water. Look, if we add it into the final dough, we're going to get ourselves
a high hydration dough. And this brings us
to a very intriguing question. What is the rationale for the
1 to 5 ratio? Most researchers use around
a 1 to 1 ratio. 1 to 2 is also quite common,
but 1 to 5 is way off. And I haven't seen any scientific explanations in the book
by Yvonne Chen on this one to five. Maybe the book is just meant to be
a simple recipe book for home bakers, so we're not going to find
what we're looking for in there. But in most scientific research,
they prefer a ratio with much less water. And here's a fun fact even
young scientists like these fifth graders, more than a decade ago
knew that one to five was way off. But maybe they didn't know about the book. Oh, they did!. Okay. But maybe there's another reason
for so much water. Is it beneficial in some other way? So while thinking about it naturally,
a few wild guesses popped up in my mind. Is it to limit the percentage of flour
used for Tangzhong or Yudane? Basically
limiting the amount of gelatinous starch. Well, that sounds ridiculous. That would mean we'd never get the full benefits of this method,
because by limiting ourselves to using less than 10% of the total flour
for our Tangzhong or Yudane, our recipes will make breads that
essentially do not have as much difference with breads made without Yudane or TangZhong, that can't be it. Researchers have shown
there are significant benefits to using 10% and above to somewhere
below 30%. Another possibility I thought of is could the extra water
be there to anticipate water evaporation? To be honest, I suspect this 1 to 5 ratio
may have its origins in the kitchen in the preparation of cooked rice, porridge
and other things like sauces or soups. So basically the starch is slowly
heated with a little stirring, which thickens the liquid it's added
to, well, I can imagine doing this using, for example, corn starch because the thickening power of corn
starch is more than that of wheat starch. Also, the gelatinization onset
temperature for corn starch is higher. So it may take a little longer
for the mixture to gelatinous. The extra water is to anticipate
a higher evaporation, but for wheat flour especially to be used in bread,
clearly there's no need for that. Okay,
but what about the science behind it? So let's have a scientific look at it. If you watched my previous video
on this topic, you already know that it starts from starch gelatinization. Starch gelatinization is at the core
of the Tang Zhong or Yudane method and as the name implies, it naturally
has to do with the starch within the flour that we use for the Tangzhong
or Yudane For gelatinization to happen, our wheat starch has to be soaked in excess water. Which is generally considered
to be 60% of water content. So three parts of water
with two parts of starch that makes a 2 to 3 starch to water ratio, weight by weight,
considering 14% moisture basis and the fact that starch
constitutes on average 68% of wheat flour, 2 to 3 translates around less than 1 to 1 ratio of flour to water. This calculation
is, of course, for bread flour. So in essence, 1 to 1 flour to water ratio is sufficient for starch gelatinization To have a better insight, let's look at the effect of water on heating wheat starch to water mixture, for percentages of water content greater than or equal to 60%, crystallites within the starch granules melt at around 65 degrees Celsius. Now, this is where it gets interesting. They found that there was not much
difference in this critical temperature for the different amounts of water
content within the range of 60 to 90%. As long as the water content is above 60%,
there's no change in the temperature that leads to this critical phase
of starch gelatinization, which makes extra water
pretty unnecessary. Actually, there is an older research paper published in 1980
that also indicates the same results. Okay, now let's go back to this
Japanese paper we talked about before. Remember, this research is based on a 2
to 1 water to flour ratio. These images show
the stages of gelatinization as the temperature progresses.
Under the microscope in polarized light, the starch granule within the Yudane loses its birefringence and its extinction cross at 65 degrees Celsius and above a clear indicator for the shrinking
of the crystalline regions within the granules, a
sign of the completion of gelatinization From table 1 of the research paper, you can also see that at 75°C, the gelatinization is said to be completed. To understand this, we need to know that
the starch granule is made up entirely of one type of building block,
a simple sugar called glucose. These simple blocks are then linked
and densely packed into linear or highly branched polymers known as amylose
or amylopectin respectively. These polymers are then
grouped into crystalline and amorphous regions,
making starch a semi crystalline material. When viewed in polarized light
under a microscope, starch granules starch granule shows its birefringence property with its extinction cross. amylose makes up about 25% of wheat
starch, while amylopectin takes up the rest, 75% in aqueous mediums at low temperatures, 0
to 40 degrees Celsius. Starch granules swell due to the diffusion
and absorption of water in its amorphous regions. The non crystalline part. This process is reversible. If you dry it, the swollen granules
can still return to their original form. Things change when you bring in more heat
at higher temperatures, starch granules undergo
irreversible transformations. The specific changes that happen vary
depending on water content. When the water content
is lower than 60% weight by weight, that is two part
starch to three parts of water. It goes through a process called melting. This may require temperature
of over 100 degrees Celsius, but that's obviously not what happens
in the preparation of TangZhong or Yudane because gelatinization requires
starch to be heated in excess water. A water content of more than or around 60%
weight by weight During gelatinization the shape and size of starch
granules change. They start to absorp more and more water
first through the amorphous regions, just like before, it causes the granules to swell, after
which water starts to get into the dense double helical structures of amylopectin,
heat causes this region to diffuse that soon followed by Amylose
dissolving and and crystallites melting with the consequence of shrinking crystalline regions, this is when you see the extinction
crosses disappear when viewed under a polarized light
microscope. More water then penetrates into
the granule, making it swell even more. At this stage, some of the amylose molecules
leach into the surrounding water and some of the granules
eventually rupture, leading to the rise
in the viscosity of the water medium. That's how you get the thickening effect. All right. That's what happens when it's hot. Once it cools down, though,
another process begins. Starch molecules reassociate
in an ordered structure through a process
that we call retrogradation. Two separate things happen
during retrogradation. The forming of a gel called gelation
and the crystallization of Amyloses and Amylopectin. Retrogradation can expel water from the starch network,
basically moving water out. When that happens, we call it Syneresis So due to the tight relation
between Syneresis and retrogradation, we can actually use it to measure
the degree of starch retrogradation. Understanding the science behind the gelatinization process is crucial to our understanding of Tangzhong/Yudane, so we can choose how to prepare Tangzhong/Yudane instead of blindly following an unsubstantiated baseless method, despite it might be very popular. So, this paper strongly shows us that the 1:2 ratio is just perfectly fine, and remember this, the ratio, as mentioned in the paper, was selected out of practicality. All of these and paired with the fact that the 1:5 ratio makes it practically impossible to achieve the recommended percentages,
as mentioned in many papers, make the Tangzhong with its 1 to 5
ratio a pretty bad choice. In conclusion,
I have now completely stopped using the 1 to 5 Tangzhong ratio. So, whatever you want to call it,
Yudane, Tangzhong, or water roux starter, I'm just going to do it this way. Basically I measure one part flour to about 1.5 to 2 parts water by weight. This is more for practical purposes,
of course. As I explained before, any ratio
you use above 1 to 1 is just fine. Extra water is just meant
to make it easier to prepare Tangzhong/Yudane compared to the basic 1:1 ratio. I bring the water to a boil,
pour it into a bowl, slowly dropping in the flour
while continuously stirring the mixture. And when it thickens,
I keep on folding the dough until I see all the flour has been fully
hydrated and gelatinized. And that's it. Our Tangzhong or Yudane or water roux starter is ready. I usually take the extra step
of measuring its total weight and when we deduct this total weight
with the weight of the flour used, we get the amount of water
within the Tangzhong or Yudane It can be quite useful for a more precise
calculation of the hydration of our final dough,
but it's not necessary. So there you have it. call it Tangzhong/Yudane/water roux starter, it is what it is. Okay, before I go, I want to also show
you how to easily convert any existing recipe
to a recipes using Tangzhong or Yudane. When writing or modifying any recipe, the easiest and widely used
method is to use what's known as Baker's percentage. In using Baker's percentage, we always start with the flour weight
and it is always expressed as 100% in total. Any ingredient after that is expressed
as a percentage of the flour weight. For example,
take this simple classic white loaf recipe by applying Baker's percentage. This recipe transformed
into this flexible format. In this format, we immediately
get the hydration of the recipe that is 70%, which is an indicator
of how wet the dough is going to be. And if you want to modify the recipe,
let's say you want to use 300 grams of flour, put that number in,
multiply it with the relevant percentages for each ingredient and you immediately
get the modified recipe. It's just as easy as that. Now let's use this basic 1 to 1 knowledge
to convert this recipe to one using gelatinized starch.
Using baker's percentage, it's actually quite straightforward. You start by deciding on the percentage of flour
you want to use for the gelatinized starch. Say you want to set aside
10% of the wheat flour for it. So here's the recipe. Easy, isn't it? Another question I get asked often is : Do we need to add extra water after this conversion? The short answer is no, definitely no, if the percentage of flour
you're using for Tangzhong or Yudane is below 10%, because at this range
the influence of Tangzhong or Yudane on our final breads
is relatively insignificant. If your bread comes out far below your expectations,
maybe you should double check the steps you take in the preparation of your Tangzhong or Yudane. I have a longer answer though, for percentages above 10%. There's a common misunderstanding
that once you make the Tangzhong or Yudane the gelatinized starch holds onto the water from the beginning of gelatinzation and all the way up to the very end. Some people even speculate
that this is what makes the bread moister. This is a bit misguided. The process of starch gelatinization is irreversible, yes, but the water absorption
isn't necessarily that way. Actually,
there are many ways to get the water out of the gelaltinized starch, in the food industry two methods come to mind vacuum
freeze drying and drum drying. Of course, we can't compare the way
we gelatinize Tangzhong or Yudane to the gelatinization process of wheat
starch in these two methods. But one thing is clear
gelatinization doesn't mean that the water is permanently retained
within the gelatinized starch, at home when we leave our Tangzhong
or Yudane in the fridge, retrogradation, as I explained before, also brings out
some of the water content and further mixing in a stand mixer
or by hand kneading will also tear the Tangzhong or Yudane apart and bring out more. So the water absorption
is to some extent reversible. The starch granules within our Tangzhong or Yudane though, have swelled irreversibly. So what exactly happens to the dough
when we add Tangzhong into it? From this research paper
we referred to before, it concludes that adding Tangzhong or Yudane increases the dough resistance. But the dough ends up having less tolerance to kneading. This is the consequence of adding a pre-gelatinized water roux that has undergone retrogradation into the dough. So will adding more water change this? Yes and no. But it's more important to consider if that's what you really want. Let me explain. Adding water at a glance may help in fixing some of the issues we mentioned above. For example,
lowering the dough resistance. But you need to take into account
the reduced amount of gluten too, because the part of the protein of
the flour that went into the Tangzhong or Yudane have been denatured, so you have less protein with which to build the gluten network, depending on the percentage of flour used in your water roux starter, adding extra water can mean raising the hydration of the bread while having less gluten overall, this is like a situation where you substitute the bread flour in a recipe with a flour of lesser protein content, or maybe this, although not exactly the same, it's like using all purpose flour in the place of bread flour
while adding more water at the same time. And that, I believe, can be like
making an entirely different bread. Most of the time we add extra water to compensate
for the loss of water due to evaporation. Also to anticipate a small part of
the water being trapped within the water roux starter, we may opt to add about 2% more water for every rise of 10%
in the percentage of flour used for the water roux starter, like it's done in this paper. And okay, that's it for today. I guess that was a lot of information
on Tangzhong and Yudane, thanks for watching and bye.
