Why does rice get sticky as it cools off? So I have noticed rice go from fluffy and easy to separate to sticky and coming off as several masses. I have a hypothesis as to why that happens. Also, I have noticed this most in long grain rice that it is sticky when it has been cooked and cooled off. 

Here is my hypothesis as to why:

As you add the cold water or broth, the starch on the surface of the rice starts to dissolve. As the temperature rises, this solubility increases and the amount of liquid decreases because some is turned into steam and the rest is absorbed by the rice. While the rice is hot, it is fluffy and you can easily separate the grains. But as it cools, the starch starts coming out of solution and forming complexes between the rice grains causing them to stick together. Once it is completely cooled off, only a small amount of the rice stays as separate grains and the rest stays as masses of rice.

But is this why my long grain rice gets sticky as it cools whereas my medium grain rice stays as separate grains hot or cold?
The reason is simple, starch will first hydrate in water and then it will gelatinize with heat. Once it cools down it will set causing it to stick.