what you buy in a store may have sat there for ages. what you grind at home is fresh. I am sure both home ground and store bought will work, but think of it like this: 1. Would I use something that I have no idea what the producer has done to ??? ( store bought) or something that I have just ground myself (fresh). Look for Brown Rice or Raw Rice and for gods sake dont make my mistake of buying the pre-steamed version. buy ecological RAW OR BROWN RICE. GRIND YOURSELF Edit: I am not 100 % on that presteamed (low cooking time) WONT WORK. Its just that I am used to the ecological stuff. So correct me if I am wrong..