Crystal noodles are made from starch and water. That’s it. The starch most commonly comes from mung beans, but sweet potatoes, potatoes, tapioca (cassava), and other plants are also used depending on the country. The simple ingredient list is what gives these noodles their signature glassy, translucent appearance once cooked.
You’ll also see them called glass noodles, cellophane noodles, or bean thread noodles. They’re all the same basic product: pure starch pulled into thin strands, dried, and sold in bundles.
The Starch That Makes Them Clear
Regular wheat noodles stay opaque because wheat flour contains proteins (gluten) that scatter light. Crystal noodles skip the protein entirely. Pure starch, when hydrated and heated, forms a gel that light passes through, which is why the noodles turn nearly transparent in hot water. The higher the starch purity, the clearer the noodle.
Mung bean starch is considered the gold standard for this effect. It produces the most consistently clear, firm noodle with a pleasant springy chew. Sweet potato starch creates a thicker, chewier noodle that’s slightly more gray or purple-tinted. Potato starch yields a softer texture. Each starch behaves a little differently in the pot, which is why the type matters even though they all look similar in the package.
How the Starch Varies by Country
The specific starch used in crystal noodles depends almost entirely on where they’re made.
- China: Mung bean starch or sweet potato starch. Chinese glass noodles (fensi) are typically thin and delicate.
- Korea: Sweet potato starch. Korean dangmyeon are noticeably thicker and chewier, built for dishes like japchae where the noodles need to hold up to stir-frying.
- Japan: Potato starch, giving a softer bite compared to Chinese mung bean versions.
- Vietnam: Two distinct types exist. Bún tàu uses mung bean starch (introduced by Chinese immigrants), while miến dong uses canna starch, a plant native to the region.
- India: Arrowroot starch, made using traditional techniques. These noodles are called falooda and are typically served in desserts, layered over kulfi (a dense ice cream).
- Myanmar: Mung bean flour. Known locally as kyazan, meaning “lotus thread.”
- Indonesia: Some regions use aren (sugar palm) starch.
If you’re shopping at an Asian grocery store, check the ingredient list to know which starch you’re getting. Mung bean versions and sweet potato versions cook differently and have distinct textures, so they’re not always interchangeable in recipes.
Nutrition at a Glance
Because crystal noodles are pure starch, they’re almost entirely carbohydrates. A 100-gram serving of dried mung bean glass noodles contains about 351 calories and 86 grams of carbs. There’s virtually no fat, very little protein, and minimal fiber. Once cooked, they absorb a lot of water, so a typical serving weighs much more but contains fewer dry calories than you’d expect from the package weight.
One notable advantage of mung bean glass noodles is their low glycemic index. A study published in the World Journal of Gastroenterology measured their GI at just 28, which falls well into the “low” category (anything under 56). For comparison, white bread scores 100 on the same scale, and brown rice came in at 82. This means mung bean noodles cause a much slower, smaller rise in blood sugar than most other starchy foods. That low GI likely comes from the way mung bean starch resists rapid digestion.
Crystal noodles are naturally gluten-free, since none of the starches used to make them come from wheat, barley, or rye. This makes them a reliable option if you’re avoiding gluten, though it’s always worth checking the label for any added ingredients in processed brands.
How to Cook Them
Crystal noodles come dried and brittle. You have two options: soak them in room-temperature water for 5 to 15 minutes until pliable, or drop them into boiling water for 2 to 3 minutes. The longer they soak, the more they expand and soften. Most recipes call for soaking first, then briefly tossing the softened noodles into a stir-fry, soup, or salad where they finish cooking.
Overcooking is the most common mistake. These noodles go from pleasantly chewy to mushy quickly. If they’re going into a hot soup or braise, add them in the last few minutes. For cold salads or spring rolls, a short soak in warm water is usually enough. Once cooked, they’ll absorb the flavors of whatever sauce or broth surrounds them, which is one reason they’re so popular in boldly seasoned dishes.
Crystal Noodles vs. Rice Noodles
Crystal noodles and rice noodles are often confused, but they’re different products. Rice noodles are made from rice flour and stay white and opaque after cooking. Crystal noodles turn clear. The texture is different too: rice noodles tend to be softer and more fragile, while mung bean crystal noodles have a bouncier, more elastic chew. Sweet potato crystal noodles are chewier still.
In terms of cooking, rice noodles break apart more easily in stir-fries, while crystal noodles hold their shape well under high heat. If a recipe specifically calls for glass noodles or crystal noodles, substituting rice noodles will change both the look and texture of the dish significantly.