Updated: Feb 3, 2022
The Asian method of bread making are starting to take an influence in the world of the baking enthusiasts. Perhaps the word "Tang Zhong" and "Yudane" bread have become a too familiar term on social media or that you are still new to the world of bread baking experience, you have no idea what these two terms really mean.
Tang Zhong or Yudane refers to the method involved in Asian bread with the sole purpose to achieving that soft bread texture that will stay soft over several days without it going stale too quickly and there is actual science behind these methods!
SCIENCE OF MAKING SOFT BREAD
If you have made bread at home, it is almost certain that you will find that your bread comes out light, airy and soft straight out from the oven and stays so whilst still warm. As the bread starts to cool, they become dry and hardy or in other word "stale", and you will often see the significant difference on day two when the bread have fully and completely cooled, even if you have wrapped and stored them well. The reason to that is because bread goes through a process call "retrogradation" once they are cooled, and this is all thanks to the starch found in the wheat flour.
RETROGRADATION OF STARCH
Retrogradation in bread is an occurrence where the main molecules in starch: amylose and amylopectin retrogrades or in other word return to its crystalline structure upon cooling, which is responsible for bread becoming stale or hard.
There are two main components in the flour that you use that plays some of the big roles for bread baking: Gluten and starch. Both of these components reacts to water or liquid in their own way that gives bread its structure and level of softness. The only difference is: Gluten is a protein and starch is a carbohydrate and they are both predominantly found in the endosperm part of the wheat grain.
When flour are mixed with water, two proteins: glutenin and gliadin starts to align from one another and form something called the gluten. Gluten is important to give you the structure (ability to hold on to air in the bread without collapsing which yield a soft interior crumb for the bread) and chewiness to your dough.
During mixing of the dough where water is added into the flour mix, the gluten forming protein will start to absorb the water and transform into gluten.
Starch is also found in flours and mainly from the endosperm part of the wheat grain. In fact, starch is important in bread making because it gelatinizes, meaning, the starch molecules absorbs water and expands during baking which is what makes your bread so moist and soft.
Starch particularly reacts along side any kind of liquid when there is presence of heat and will start to swell and absorb water at a temperature of 60˚C, which is where it begins to gelatinise. This means that during mixing of the bread dough before baking, it doesn't do much with the presence of water, therefore does not interfere whilst the gluten proteins are interacting with the liquid. However, once the bread are proofed and is place in the oven for baking, the gluten starts to coagulate and the starch will begin to draw the water out from the remaining liquid present, holds on to them and then expand when heated. During this process, some liquid can also be lost through evaporating steam.
The whole interchanging of water in the bread making process between gluten, other ingredients like water and salt with starch creates a water-scarce environment. This is why the Yudane method makes complete sense. When preparing the Yudane, a small part of the flour are mixed with boiling liquid and kneaded together to form into a stiff dough. By implementing hot boiling water to the flour, the starch begins to pre swell and absorb all of the the liquid added to it without having to compete with other ingredients. Once the starch has swelled and retain the liquid, it stays in an irreversible state all the way through to final baking. Therefore no water is scarce or lost to the gluten protein and other hygroscopic ingredients nor due to the evaporation from steam during baking. This results in a softer bread that retains the moisture for a longer period of time. In other words, the Yudane or Tang Zhong Method allows the dough to hold on to more water that would otherwise be lost due to the mentioned factors without the dough becoming too soft to handle.
DIFFERENCE BETWEEN YUDANE AND TANG ZHONG METHOD
Both the Yudane and Tang Zhong method is very similar with the same application of science to making soft bread. Tang Zhong method is in fact an adaptation to the original Japanese Yudane method. The only difference between the two method is that Tang Zhong is made from whisking and cooking a small part of flour in the recipe with liquid (milk or water) until it starts to gelatinize in to a paste. This paste is often referred to as "Water Roux" in English which is a direct translation from the Chinese Origin of the word Tang Zhong. The amount of flour often used to make Tang Zhong is around 8-10% of the total of flour in the recipe, subtracting what was removed for the Tang Zhong in the Final Dough recipe. The amount of liquid used are usually 1 part flour to 4 - 5 part liquid.
Yudane, on the other hand is prepared by adding boiling hot water to a small amount of flour in the recipe to make a stiff dough, usually 20-30% of the total amount of flour in the recipe, subtracting what was taken out for the Yudane in the Final Dough recipe. The amount of boiling liquid are usually 1:1 ratio to the amount of flour in the Yudane. This stiff dough is then wrapped and left to cool before being broken to smaller pieces to be added in with the rest of the ingredients.
DOES YUDANE OR TANG ZHONG BREAD EVENTUALLY GOES DRY?
Like any bread, there will be a time when it will eventually become stale. It is just the nature of the crystalline structure of starch as explained earlier. This is the same with Yudane or Tang Zhong based bread, but because a small part of the flour are pre swelled with a large amount of water, the Yudane dough or Tang Zhong paste are able to retain more moisture that would otherwise be possibly lost by some percentage during mixing and baking, this allows the bread to stay soft for longer before the retrogradation process occurs.
Equipment: 200mm length x95 mm width x 95mm height loaf tin
Yield: 1 loaf
70 g White Bread/Bakers Flour
70 g Boling Water
For Final Dough
Above 60% Yudane 85 g 34% Bread Flour 150 g 64% Whole meal Baker's Flour 4 g 1.7% Instant Dry Yeast 40 g 17% Fine Sugar 4 g 1.7% Fine Salt 80 g 34.8% Whole Milk 85 g 36% Egg (whisked) 30 g 1.3% Unsalted Butter 60 g ----- Sunflower Seeds
50 g Full cream Milk
50 g Eggs (1 egg)
To make the egg wash, whisk the two ingredients together and set aside in the fridge until ready to use.
For the Yudane
Boil the water and whisk in the flour until it starts to form into a semi stiff dough. Wrap the yudane dough and leave at room temperature to fully cool down before adding into the final dough.
Note: The yudane dough can be pre made the night before and stored in the fridge. However, before using the yudane straight from the fridge, allow for it to come to room temperature before adding into the final dough.
For the Dough
1. Whisk together the eggs and milk in a bowl. Place the flours, instant dry yeast (away from contact with salt and sugar), sugar and salt in a stand mixer bowl fitted with a dough hook.
Break the Yudane into smaller pieces and add them into the rest of the ingredients followed by the whisked liquid.
2. Mix the dough over low speed for approximately 3 minutes until all the ingredients have come together to form a dough. At this point, the dough should still look quite rough.
Increase the speed to medium and mix for a further 3 minutes. Add in the cubed room temperature butter a little at a time and continue to mix over medium speed for another 5 minutes or until you are able to gently stretch the dough between both your hands without it breaking too easily.
3. Lastly, add in the sunflower seeds and mix in small burst until they are incorporated into the dough. Do not over mix at this stage as this can cause the nuts to break the gluten structure of the bread.
4. Lightly grease a bowl large enough for the dough to double in size, transfer the dough onto a work bench. Dip your hands lightly into some flours (avoid adding additional flour to the main dough) and roll the dough into a smooth ball. Transfer the dough, seam side down, into the oiled bowl, cover and leave to bulk ferment for 90 minutes to 2 hours or until it double in size.
Note: Depending on the ambient of your kitchen, bulk fermentation time can be shorter or longer.
5. Once the dough are ready and have doubled in volume, lightly dust the work bench with some baker's flour. Transfer the dough over the flour and divide the dough in to two equal portion of roughly around 315 g each.
Roll each portion into a rectangle. Lenghtways, fold one end one third of the way to the center, press the ends down then fold the opposide ends over to to fully cover the top.
Turn the dough 90 degrees with the open ends on the north and south side from you. Roll the dough with a rolling pin to a longer rectangle to around 16 cm in length or long enough for you to roll the dough from the top towards you with three folds.
Place each final rolled dough with the seam side underneath into the pre lined loaf tin leaving some gaps on both sides of each portion of the dough to allow them to expand and rise again.
6. Cover the loaf tin and leave to final proof for approximately 1 hour to 90 minutes or until increases double its volume again.
Meanwhile, pre heat the oven to 170°C.
7. Once the dough have risen again, whisk the eggs and milk together and lightly brush the top of the loaf with the egg wash.
Bake in the pre heated oven for approximately 30 minutes or when the internal temperature reaches 87°C - 90°C.
8. Remove the yudane loaf from the oven, very carefully tilt the loaf out on to a wire rack to allow it to fully cool.
Note: leaving the bread to cool in the baking tin will cause it to sweat and can make your bread soggy.
Wrap the dough tightly with cling wrap and store at room temperature (never in the fridge). The bread will stay soft even after a week if stored correctly!