I beg to differ on the issue of processing. The biggest change you can make to the GI of a food is to grind it smaller, with or without the fiber included. Well, actually, the biggest impact you can have on the food is how you cook it, followed by how finely it is ground. Both cooking and milling increase the rate of digestion, which is the main determinant of a starches GI if eaten on its own. other big factors are what you eat it with...adding fats certainly slows the digestion and thus the GI of a food, so taking something like potato, raw potato has a pretty low GI, boiled potato around 78, instant mashed potato more like 87, yet fries are only 63 thanks to all that fat slowing their absorption.
You mention rice. My info is that white rice has a GI around 73, brown rice around 68...not a huge difference, and the difference can be attributed to the bran of the brown rice still surrounding the starch, thus slowing digestion. If you were to pulverise both rices so the stomach didn't have to digest the bran to get to the starch, the GI of the brown would increase.
And the third thing to consider is cooking time. The longer you cook something, quinoa, oats, rice, etc...the higher the GI. So think of home cooked quinoa that is then dehydrated and cooked again as twice cooked. Personally, I don't put much stock in GI measures because of this. I prefer to think in terms of glycemic load, where what IS ineveitale is how much glucose you will be consuming. The rate of absorbing the glucose can be varied by processing, fiber, cooking, eating with or without fats or proteins, but total amount of glucose remains the same. GI is of more use to IDDM folks who need to work out how much fast versus slow acting insulin they may need after a meal, but total insulin remains pretty much the same. I have nothing against quinoa, or any other whole food, but I would like people to understand that the very thing that makes a whole grain (or legume) "inconvenient" to cook in the backcountry is also one of the things that makes it lower GI. Maybe our bodies just weren't designed for fast food....or maybe we worry too much about the details. After al, te concept of GI only applies in a vacuum in which no other food is eaten at the same time. Use flaked grains and throw in some olive oil or cheese and don't worry about it maybe...