Rice – Does glutinous rice contain gluten

I went into some detail with this in my answer to What are the factors that affect the chewiness, softness, moisture of bread based desserts like cinnamon rolls?

To summarize my points there and add some more (simplified) detail on the chemistry:

• Gluten is responsible for elasticity of dough, which is perceived as chewiness. The difference between bread, quickbread (muffins/scones), and cake is largely due to the difference in gluten formation, with cake having the lowest amount and bread having the highest.

• It does not directly cause rising - the leavening agent (yeast, baking powder, etc.) is responsible for that. What it does do is form a protein network by cross-linking, which not only results in the elasticity above but also traps gas and prevents it from escaping during the baking process. The "rising" in baked goods is essentially just stretching of the gluten network. This is why hydrocolloids such as xanthan and guar gum can mimic some of the effects in gluten-free recipes; although the mechanism is completely different - in essence, they're creating a very thin gel.

• Gluten is also exceptionally good at both absorbing and retaining moisture; it can absorb up to 150% (1.5 times its own weight) in water. One thing you'll notice about typical wheat products vs. their gluten-free equivalents is that latter don't last too long and have to be frozen or consumed quickly. Part of this is due to preservatives in commercial baked goods, but much of it is also simply due to the gluten retarding moisture loss. You can think of it as a kind of natural preservative.

• It's activated by water and heat and is (relatively) slow-acting, which gives it a high tolerance with respect to time and temperature. This is why many people will tell you that bread is "forgiving" while cake and other low-gluten/gluten-free products are not. When baking without gluten, you will have to be very precise about all of your measurements.

• Its coagulation action is actually very similar to that of egg whites, and pure gluten (AKA vital wheat gluten) is sometimes actually used as a replacement for egg whites. A meringue is just heavily aerated egg whites and specifically protein; gluten is basically doing the same thing inside of whatever you're baking.

• Finally, it provides nutritive protein when eaten. Wheat gluten is about 75% protein and all-purpose flour is about 10% gluten. That means 7.5% of the flour you consume is actually protein. Of course that's nowhere near what you get from meat, but it's still a significant contribution to one's diet.

In short: Gluten does a lot of things. Keep in mind when doing gluten-free baking that a lot of the substitutes only replicate one or two of the effects.

I would not follow the advice of boiling them for three hours, you will likely have nothing left! I would not boil them at all in fact, most dumplings you get from asian supermarkets in western countries are made so that they can be steamed from frozen for 15-30 minutes and then eaten. They are often produced for the catering trade, you see, so quick cooking times are important. The picture you posted looks like they are possibly fried, but it's hard to tell.

I am making the assumption you are not in Asia, and this is a specialist supermarket, so I would simply call up the supermarket and ask. It's pretty likely someone there will be able to speak with you.

If not, the important thing is to make sure that the dumplings are cooked throughout to at least 160F (72C), this will at least make them safe. I'd recommend using a digital instant-read thermometer for the job. The three methods I know of to cook pre-made dumplings are:

• Steam: you can use a bamboo steamer if you have one, but any steamer will do really. If you can get banana leaves use them to line the bottom, but if not use something to line the bottom of your steamer because these things stick like glue!
• Fry then steam: this is done with a wok, you brown the dumplings in the wok in some oil, then you pour a bit of water in and cover. The dumplings then steam under the cover, and the oil gets vaporized as well giving the dumplings a nice sheen. I've only used this for small wonton-style dumplings, I wouldn't recommend this method for your big ones although there's no reason you couldn't try it. Just remember that pouring water into hot oil causes spurts, a top tip from me to avoid being singed would be to hold the cover over and pour the water in through a small gap. Keeps the mess down as well
• Deep frying: I'm sure shallow frying would work as well, however you must thaw these out before frying them. Throwing frozen dumplings straight into a pool of boiling oil is dangerous! I don't have a deep fryer and I don't like the mess of shallow frying so I avoid dumplings that require this. Also, not many dumplings are deep fried

All in all I'd try steaming one of them for 25-30 minutes and then testing it. Vary the steaming time accordingly.