From Mung Beans to Glass Noodles: How Mung Bean Vermicelli is Made

What Are Mung Bean Vermicelli?

Mung bean vermicelli, often called glass noodles or cellophane noodles, are thin, translucent noodles made primarily from mung bean starch. Unlike wheat or rice noodles, they become almost transparent when cooked, with a slippery, slightly chewy texture. They are a staple in Thai cooking, used in salads, stir-fries, soups, and spring rolls. Their neutral taste allows them to absorb the flavors of sauces and broths, making them versatile in many dishes.

You can recognize them by their dry, brittle, white appearance before cooking; after soaking or boiling, they turn clear and soft. They are sold in dried bundles, often labeled as "mung bean vermicelli" or "glass noodles." In Thai cuisine, common dishes include pad woon sen (stir-fried glass noodles with vegetables and protein) and yum woon sen (spicy glass noodle salad).

From Mung Beans to Starch: The First Step

The journey of glass noodles begins with mung beans, small green legumes. The key ingredient is mung bean starch, which is extracted from the beans through a process of soaking, grinding, and separating.

How Mung Bean Starch Is Extracted

1. Soaking: Dried mung beans are soaked in water for several hours or overnight until they become soft and swollen.
2. Grinding: The soaked beans are ground into a fine slurry using a stone mill or modern grinder.
3. Separating: The slurry is mixed with water, and the mixture is passed through sieves or cloth to separate the fiber and protein from the starch. The starch settles at the bottom of the container.
4. Drying: The settled starch is collected and dried into a fine white powder, ready for noodle making.

This mung bean starch is prized for its high amylose content, which gives the noodles their distinctive firmness and clarity after cooking.

Making the Noodles: From Starch Slurry to Thin Strands

Once the starch is prepared, it is transformed into noodle strands through a process involving starch gelatinization and extrusion.

Starch Gelatinization

Starch gelatinization is the process where starch granules absorb water and swell when heated, forming a thick, translucent paste. For glass noodles, mung bean starch is mixed with water to create a slurry, then heated while stirring until it becomes a smooth, glossy dough-like mass. This step is crucial because it gives the noodles their elastic, cohesive texture.

Noodle Extrusion

The hot, gelatinized starch is then forced through a noodle press or extruder with small holes to form thin strands. The strands are extruded directly into boiling water to set their shape, then immediately cooled in cold water. This rapid cooling stops the cooking process and helps the noodles maintain their springy texture.

Noodle Drying

After cooling, the noodles are drained and hung on racks to dry. They are often folded into bundles or cut into uniform lengths before drying completely. Once dry, the noodles become brittle and can be stored for long periods without spoiling.

The entire process requires careful control of temperature and consistency to ensure the noodles are smooth, clear, and free of lumps.

How Glass Noodles Are Used in Thai Cooking

In Thai cuisine, glass noodles are valued for their ability to soak up flavors while retaining a pleasant chewiness. They are commonly stir-fried, tossed in salads, or added to soups.

• Pad Woon Sen: A classic stir-fry where soaked glass noodles are tossed with eggs, vegetables, and sometimes meat or seafood in a savory sauce made with soy sauce, fish sauce, and a touch of sugar.
• Yum Woon Sen: A spicy and sour salad featuring glass noodles mixed with lime juice, fish sauce, chili, and fresh herbs, often with minced pork or shrimp.
• Spring Rolls: Glass noodles are sometimes used as a filling ingredient, adding a delicate texture alongside vegetables and protein.

To prepare dried glass noodles for cooking, soak them in warm water for about 10–15 minutes until they become pliable, then drain. They can then be added directly to stir-fries or briefly boiled for soups. Unlike wheat noodles, they cook very quickly and can become mushy if overcooked, so they are often added at the end of cooking.

Comparing Glass Noodles with Other Noodles

To better understand glass noodles, it helps to compare them with other common Asian noodles:

Glass noodles are unique in their clarity and springiness, which comes from the mung bean starch. If you need a substitute, rice vermicelli can sometimes work in a pinch, but the texture will be softer and less chewy, and the dish will look different. In recipes where the translucent appearance matters, such as in some salads, there is no perfect substitute.

Simple Tips for Cooking Glass Noodles at Home

• Soak, don't boil: For most stir-fries and salads, soaking in warm water is enough. Boiling can make them too soft.
• Cut them shorter: Dried glass noodles can be very long; use kitchen scissors to cut them into manageable lengths after soaking.
• Flavor the sauce first: Because glass noodles are bland, ensure your sauce or dressing is well-seasoned before adding the noodles.
• Add at the end: In stir-fries, add soaked noodles near the end of cooking just to heat through and absorb sauce.

With these techniques, you can enjoy the delightful texture of glass noodles in your own Thai-inspired dishes.