What is the difference between risotto rice and paella rice?
My local supermarket stocks arborio and carnaroli rices for making risotto, and also stocks "paella rice". I have, in the past, used them interchangeably in both risottos and paellas. Wikipedia handily summarises the difference between carnaroli and arborio here, but I can't find a description of the differences between these and a paella rice (aside from country of origin).
Note: I'm aware that the rice is cooked differently in a paella compared to a risotto -- I'm asking about the differences in the rice itself, not the cooking method.
'Paella rice' is not actually a variety of rice, but a category suitable, as the its name suggests, for making paella. Some common varieties are: Bahia, Balilla, Bomba, Senia, and Calasparra; the particular variety should be indicated on the packet that you choose.
These varieties differ from risotto rices, such as arborio and carnaroli, in not creating a creamy 'sauce' around the rice. Paella rice should stick together, but be distinct and not in a creamy 'sauce'.
Arborio rice has a creamy, chewy texture due to its higher amylopectin (one of two components in its starch) content. Paella rice absorbs more liquid than risotto rices, however it too would become 'creamy' if you stirred it like a risotto, since it also has a high starch content.