This is, as the kids say, cap. Popcorn works because the outer hull is strong enough to hold together until a critical mass of pressure builds inside to rupture it. At that point the starches, which have liquefied under pressure, explode and unliquify rather suddenly. White rice and pearled barley have their hulls removed. You can see in the picture that the barley has split, but not popped, and the rice just looks a…
Perhaps puffed is a better word than popped. While it is true that puffed rice is currently made using large pressure swings, people online claim rice has been puffed using "hot salt frying" ( https://en.wikipedia.org/wiki/Hot_salt_frying ) for hundreds of years ( https://nitter.net/whetstone_mag/status/1564282053025210368?... , https://en.wikipedia.org/wiki/Puffed_rice ) and supposedly there is a secondary source da…
Cook-and-then-fry (with various frying methods) seems to be the commonly-documented method for home puffed/popped rice.