Does Rice Have Gluten?
By Ivan Nikolov
The main storage protein of rice is glutelin. Because of this, one would think that rice contains gluten..
Let’s find out if that’s true or not. Read on…
There are two types of storage proteins in cereal grains - globulins and prolamins. Both types of storage proteins can be found in most cereal grains, including wheat and rice.
In wheat and other cereal grains in the wheat family (Triticum), the main storage proteins are the prolamins - found in the endosperm (the inner part of the grain, where the starch is).
In rice and oats the main storage proteins are globulins, again mainly found in the endosperm.
Here is where it really gets confusing for most people (even for me, if I don’t often refer to the literature):
Prolamins are soluble in alcohol, but not in water or salt solutions. Globulins are soluble in salt solution. Because rice proteins, although in the group of the globulins, are not soluble in salt solutions, like prolamins. That’s why they are called glutelins.
Glutelins, in general are mostly prolamin proteins. And, those in the wheat family (Triticum) contain gliadin - the protein, which is the main cause for celiac disease, as well as mild gluten sensitivity. It is also the protein that forms gluten, when it binds to glutenin (only when mixed with water) - the other protein in wheat.
Are you still with me?
Rice proteins are not pure glutelins, which belong to the insoluble in water prolamins. And, because rice proteins do not belong to the wheat grass family prolamins, they do not contain neither gliadin, nor gluten (which does not exist as a stand-alone protein, but is rather a bond between gliadin and glutenin).
So, there you have it - the storage protein in rice is called glutelin, which doesn’t have anything to do with gluten. Rice is gluten free.
Finally, if this is somewhat confusing, don’t feel bad. It’s confusing to me, too…
References:
“Cereal seed storage proteins: structures, properties and role in grain utilization”
Peter R. Shewry and Nigel G. Halford
“Seed storage proteins”, “Gliadin”, “Glutelin”, “Prolamin” in Wikipedia