Steamed Bun Filling Stays Dangerously Hot | Generated by AI
Question: When eating dou sha bao (red bean paste bun), after steaming it with hot water for 20 minutes and then leaving it on the desk for just 2 minutes, the surface feels okay to eat, but the inside filling is still very hot and can burn your mouth. Why does this happen?
Answer:
This is a very classic and very dangerous characteristic of steamed stuffed buns / soup dumplings / big meat buns / red bean paste buns etc.
Main reasons why the inside stays very hot while the outside cools quickly
-
Very strong heat insulation effect of the dough/skin
→ The steamed bun skin + the air layer inside act like a very good thermal insulator (like a thermos) -
Huge difference in heat capacity
Red bean paste / lotus paste / custard / meat with lots of juice → contain a lot of water
→ water has very high specific heat capacity (takes a lot of energy to heat up, and also releases a lot of heat when cooling down) -
Very small surface area compared to volume
Inside filling → big ball of hot stuffing
Outside skin → relatively very thin layer
→ The surface area to volume ratio is very small → heat escapes very slowly -
Almost no air convection inside the bun
The hot filling is almost completely sealed inside
→ cannot lose heat through fast air movement (convection)
Quick comparison table (how fast different parts cool down)
| Part | Cooling speed | Main reason |
|---|---|---|
| Outside skin surface | Very fast | direct contact with air |
| Skin middle layer | Medium–fast | heat conducts outward |
| Filling edge | Medium–slow | still has some heat conduction |
| Center of the filling | Extremely slow | excellent insulation + huge heat capacity |
Practical painful experience ranking (from most dangerous to safer)
- Soup dumpling (xiaolongbao) ← most dangerous
- Big pork bun with lots of broth
- Red bean / lotus paste / custard bun ← still very dangerous
- Pure red bean paste (no much water) ← less dangerous
- Vegetable bun / mushroom bun ← relatively much safer
Quick safety tips when eating very hot filled steamed buns
- Never bite directly when it’s just taken out
- Wait at least 6~10 minutes (better 10~15 min)
- Tear a little hole first → let hot steam & hot liquid come out
- You can also cut it in half with chopsticks or spoon
- Put it on a plate and let it release heat for a while before eating
Enjoy your dou sha bao〜
but please don’t burn your tongue ~~ :( ~~