Even though I thoroughly enjoy a good grapefruit, I avoided grapefruit smoothies for a long time because I was afraid of them being too bitter. I recently decided to try making one for variety and it was actually quite good. For starters I recommend using either a small grapefruit or a half because it can still be pretty bitter.
Makes ~32 oz, or 2 medium servings. I peeled the grapefruit the same way I do oranges and removed the visible seeds. Blend on high until smooth and enjoy.
I tried this with several grapefruit varieties and close relatives of grapefruit. I tried Ruby Red, oro blanco, cocktail grapefruit, and pomelo. Our favorites were the ruby red and oro blanco, although they were all good. Also, there can be quite a bit of variation within a single type, so picking a top quality fruit is probably more important than the variety.
Russ Parsons has a short section on grapefruits in How to Pick a Peach. He recommends choosing heavy fruits with smooth skins and avoiding fruits with a recessed stem end.
If you want to go deluxe, you could use a grapefruit knife to remove the fruit from the membrane in sections, as the membrane adds some bitterness. I did not remove the membranes for the smoothies, but when I eat grapefruit straight I do like to scoop the fruit out of the membranes. I don’t often go for task-specific kitchen tools, but I have a soft spot for the grapefruit knife.Finally, remember that compounds found in grapefruit interact with some drugs, so if you or someone you feed is taking anything, make sure you check.