I'm late to the post, but I just read in the Sneaky Chef books that you can put 1/4 an avocado in fruit smoothies. It doesn't affect the taste or color, just adds nutrients. I made a bunch of smoothies to freeze yesterday with the avocado added and had the whole family taste test. No one knew! If you google Sneaky Chef's Sinless Smoothies you might be able to find the whole recipe.