All About Wheat Flour

Similarities and Differences Between Baked and Steamed Bread

There are many similarities between Western bread and steamed bread. Western bread and steamed bread are both fermented wheaten products. Both are light, porous, flavorsome, and easily digested. Production steps are similar for both, except that Western bread is baked in an oven above 200°C, whereas steamed bread is cooked in a steamer. The differences are described below.

1. Ingredients
The majority of steamed breads require only wheat flour, water, and yeast or sourdough. Guangdong-style steamed breads may contain additional ingredients such as fat and sugar. In Western bread making, other ingredients such as fat, sugar, salt, milk powder, emulsifier, and bread improvers are commonly used. Western bread requires flour with higher protein content and good protein quality compared with steamed bread (Rubenthaler et al., 1992), while a wider range of protein content is suitable for steamed bread (Huang and Hao, 1994). Flour color is more critical for steamed bread, as it should have a white, smooth skin and white crumb. Chinese steamed bread doughs have 10–15% less water added than Western bread doughs. This results in a characteristic fine, chewy texture, which is preferred by consumers.

2. Baking
Western bread is baked in an oven at over 200°C, while steamed bread dough is steamed at about 100°C. Steamed bread has a white, soft, and moist skin and has a specific volume between 2.0 and 3.2 mL/g. Bread dough forms a brown and hard crust during baking and has larger specific volume (over 4 mL/g). Western bread has a stronger, baked flavor than steamed bread due to baking at high temperatures.

3. Lysine Availability and Acrylamide Formation
Baking in a conventional oven results in browning of the crust and, to a lesser extent, darkening of the crumb. This is due to the Maillard reaction in which reducing sugars react with amino groups including lysine. Although the lysine content of steamed and baked bread are similar, lysine availability is higher in
steamed bread. This is due to the effect of heating during baking resulting in browning (Tsen et al., 1977).
Steamed products were found to have a lower acrylamide level than those that have a baked crust because more than 99% of the acrylamide comes from the crust (Surdyk et al., 2004). Acrylamide is a neurotoxin, carcinogenic in animals, and a probable human carcinogen (Lignert et al., 2002). Acrylamide has not been detected in steamed bread (Zhang, 2010).

4. Shelf Life
The steaming process raises the water activity of steamed products and provides suitable conditions for mold and bacterial growth. By contrast, bread dough loses moisture during baking and forms a hard crust. The addition of emulsifier, fat, and vinegar or other preservatives to Western bread can result in a shelf life of up to 5 days. Steamed bread can only be kept for 1 day in summer and 2 days in winter (Faridi and Rubenthaler, 1983).

Refferences : Steamed Breads Ingredients, Processing and Quality. by : Sidi Huang and Diane Miskelly