Been searching around the web for answers, none found. My guess is that it's uncooked rice (as "unedged" rice doesn't make any sense).
Before cooking rice, many people wash the rice by "grinding" (hence 研ぐ) the individual grains against one another under flowing water until the water runs more or less clear. (In the olden days the purpose of the grinding was to remove the hull (糠【ぬか】).)
In the process of this, together with rest of the hulls and dust, minerals and starch are also removed.
In any case, お米を研がず means "without washing the rice (rigorous/vigorously)".
According to the dictionary 研ぐ may mean "to wash in water" (水の中で洗う): http://dictionary.goo.ne.jp/je/53967/meaning/m0u/%E7%A0%94%E3%81%90/
So 研がず means "unwashed".