Water Temperature in Dumpling Wrappers

In the recent post about starch in flour, we discussed the effect of water temperature on doughs. In Chinese cooking, different ratios of hot and cold water are combined with flour to make dough for everything from noodles to chive pockets to dumplings, all of which differ in both texture and cooking method. To explore how water temperature adds so much versatility to dough, we made dumpling wrappers using a cold water dough and a hot water dough. We then boiled or steamed both types of dumplings and compared their textures.

Experiment Overview

Goal: To taste differences in dumpling wrappers made from cold water and hot water doughs
Recipe: Adapted from Homemade Dumpling Wrappers and How to Make Steamed Dumplings, Two Ways by Red House Spice
Method: Prepare two doughs, one with room-temperature water and one with boiling water. Wrap dumplings, boil or steam, then taste.
Results: Between the two types of dumpling wrappers, we noticed differences in
– Water absorption
– Dough elasticity
– Texture
Conclusions: Hot water is more readily absorbed by flour. Cold water encourages gluten development. Water temperature changes the consistency of the dough and the texture of the cooked wrappers, allowing us to adapt our dough to our favorite cooking methods.

Test Method

Ingredients and Equipment

• 240g Baker’s Corner All-Purpose Flour, divided
• 62g + 120g water, divided
• Dumpling filling
• Large pot
• Steamer

Making the dumplings

1. Divide flour into two portions, 120g each. To one portion, add 62g water at room temperature and stir until a cohesive dough forms. Cover with a damp towel and rest for 10 minutes. This is the cold water dough.
2. In the meantime, bring 120g water to a boil. Pour 68g of the boiling water into the second portion of flour, discard the remaining water, and stir. Knead the mixture into a cohesive dough, then cover with a damp towel. This is the hot water dough.
3. Knead the rested cold water dough until smooth. Rest both doughs for 45 minutes and prepare the dumpling filling in the meantime.
4. After resting, divide each dough into 16 pieces (11–12g each), roll each piece to approximately 3″ in diameter, and wrap 15g filling per wrapper. Boil eight of each type of dumpling with 3 additions of water and steam the other eight for 10 minutes over medium heat as described by Red House Spice. Taste and analyze.

Results

To better understand some of these results, I suggest reading through the last few posts about starch, especially the introduction and the one specifically about starch in flour. At the beginning of the flour post, I describe the effect of water temperature on dough. It may also be worth reviewing the introduction to gluten, since we’re going to be contrasting the texture of starch with that of gluten.

Water absorption

As you may have noticed from the Test Method, we used the same amount of flour in both doughs, but we added more water to the hot water dough than the cold water dough. Because flour absorbs more hot water than cold water, we can add more boiling water to the hot water dough without making it softer than the cold water dough.

Flour is 68–75% starch, and starch can absorb a lot of water. Just think about how much water rice absorbs when we cook it. But starch molecules are packed tightly together, and in order for water to be absorbed, the water needs energy to wriggle into the cracks between the molecules. Heat is a form of energy, so the hotter the water, the more easily it separates the starch molecules, the more the starch absorbs. In our doughs, the starch absorbed more boiling water, so we needed more water in our hot water dough to make it the same consistency as our cold water dough.

Dough elasticity

Although the two doughs had a similar firmness, their textures differed. The hot water dough felt like Play-Doh modeling clay, whereas the cold water dough sprang back if we pressed it. This difference in texture reflects the amount of gluten in each dough. Remember that gluten is elastic. The cold water dough was more elastic than the hot water dough, so it returned to its original shape if we stretched or poked it.

Why does water temperature affect gluten? Remember, gluten is formed from two proteins in flour, one of which is shaped like a Slinky coil. In dry flour, the proteins are immobile. But when we add cool water, the proteins unfreeze. As we mix or knead the dough, we bring these proteins together and link the Slinky coils into a large, stretchy web of gluten. It is this web that pulls the dough back into shape if we press it.

The same thing happens in the hot water dough, except for one crucial difference. The high temperature of the boiling water denatures the proteins that form gluten, which means they lose their shape. Without their shape, the proteins can’t link up very well, and the resulting gluten webs are small and scattered. Because of this, the hot water dough doesn’t have the elasticity of the cold water dough.

This has several ramifications for how we work with these doughs. First, because the extensive gluten network in the cold water dough is elastic, the cold water dough needs to be rested throughout the cooking process. This gives the Slinky coil proteins time to adjust and relax into their new alignment so the dough doesn’t spring back when we try to roll it out. Hot water doughs, on the other hand, don’t need to rest because there’s barely any gluten to fight against. This also makes hot water doughs easier to roll out. Without gluten to pull the dough back on itself, we can roll hot water doughs thinner. Dough thickness is important for the final texture of the dumpling, and as we’ll see in the next section, the ideal thickness depends in part on the cooking method.

Wrapper texture

Cooking method: steam versus boil

Among the four types of cooked dumplings (hot or cold water dough, steamed or boiled), the most obvious differences in texture were based on cooking method. The steamed dumpling wrappers were tougher, while the boiled dumplings were softer and chewier. The steamed dumplings were also yellower, and their color darkened as they cooled while the boiled dumplings remained white. These differences reflect the amount of water the dumpling wrappers absorbed as they cooked.

The water molecules in water are packed much more tightly than those in steam. This is part of the definition of a liquid versus a gas. As a result, the dumplings in the boiling water are surrounded by hundreds of times more water molecules than the dumplings in the steamer. The starch in the boiling dumpling wrappers absorbs this water (just like pasta noodles), so the cooked wrappers contain plenty of moisture. The water also gelatinizes the starch in the dumpling wrappers, which holds onto water even when the dumplings are removed from the pot and served.

The steamed dumplings, on the other hand, don’t have much water available to absorb. As we discussed in the context of steaming versus baking bread, dough doesn’t readily lose water in a steamer because the environment is moist. But there aren’t many water molecules rising past the dumplings for the starch to absorb. As a result, the steamed dumpling wrappers are drier and tougher than the boiled ones. And because less starch absorbed enough water to gelatinize, the dumplings dry out more easily when they’re removed from the steamer.

Because steamed dough absorbs less water, it’s typically rolled thinner to avoid unpleasantly tough wrappers. Boiled dumpling wrappers, on the other hand, need to withstand the turbulence of the boiling water, so they tend to be thicker. For this experiment, I kept the wrappers a similar thickness.

Type of dough: hot versus cold water

Within each cooking method, cold water dough made chewier dumplings than hot water dough. This was especially evident in the steamed dumplings after they cooled. Because the cold water dumplings contained less water in the dough than the hot water ones, they became unpleasantly dry and tough. Even when the dumplings were freshly steamed, the cold water dumplings were slightly chewier because they contained less moisture and more gluten.

In the boiled dumplings, the difference in texture wasn’t as stark because the starch in both types of wrappers absorbed water and gelatinized as it cooked. However, the cold water dumplings were slightly chewier because they contained more gluten. Gluten has a tough texture, which lent the boiled dumplings a pleasant bite.

Conclusions

Hot water is more readily absorbed by starch in flour, and it denatures gluten proteins. As a result, hot water doughs differ from cold water doughs in properties such as water absorption, dough elasticity, and wrapper texture. Steamed dumplings are often made with hot water dough. Because the dumplings won’t absorb much water as they cook, it’s preferable to use a dough with more water and less gluten so it rolls thin and remains tender. Boiled dumplings are typically made with cold water dough. Since the starch in the flour gelatinizes as the dumplings cook, the limited water and developed gluten in the dough won’t make the dumpling unpleasantly tough, and the wrappers can withstand the turbulence of boiling water. Doughs made with a mix of both hot and cold water yield intermediate textures. So by merely adjusting the temperature and ratio of water, we can create doughs for foods as diverse as boiled noodles, steamed soup dumplings, and pan-fried chive pockets.

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