Sectioning is the process by which you separate the fleshy part of the citrus fruit from the tougher membrane. In most citrus fruit such as lemons, limes and oranges the membrane is actually not that tough, but when it comes to things like grapefruit the membrane is damn near inedible. Most types of citrus can be sectioned pretty easily. In this form they work well in fruit salad, or just chilled in a bowl which is the way I prefer to eat grapefruit as opposed to the tried and true method of slicing it in half and digging in with a spoon. It tends to be less work to just section the grapefruit and you don't end up shooting your self or your sister in the eye.
So now that I've convinced you all of the wonderful thing that is sectioning, you may be wondering how to do it. Well, it goes a little something like this.
Preparation: First, you will want a bowl to catch the fruit and the juice, a cutting board, and a very sharp knife. If you do not use a sharp knife you will make juice and a mess, and you will be left unsatisfied.
- Take your fruit (I will assume a grapefruit) set it on its side and cut off the top and bottom. You should be able to see the "meat" where you cut on both ends. If you cannot, take a little more off until you can. If you do not do this the sections will be difficult to remove when you are finished.
- Turn your fruit so that it is resting on one of the ends you just cut. Now we will remove the peel and outer membrane. Taking your knife, start at the top edge near where the peel touches the "meat". With a slicing motion remove small sections of the peel. Try to follow the curve of the fruit or you will loose a lot of edible stuff. Rotate the fruit around, taking off small sections until the fruit is completely naked. There should be no rind or outer membrane left. If there is carefully trim this off.
- You are now ready for the actual sectioning part. Take the fruit in your left hand (right hand for lefties) and hold it out in front of you, preferably over the bowl as this is going to get rather messy. You should clearly be able to see the membranes between the sections, they will look like white lines and should stand out against the flesh of the fruit. Taking the knife in your other hand cut on either side of all of the membranes (at no point should the blade of the knife go more than half way through the fruit). Use a light touch, and remember, citrus fruit with blood is not very tasty. This will release each individual section. Avoid removing the sections as you cut them, if you do you will be left with a soggy lump when you get to the end and the last few sections will be difficult to cut.
- Once you are done cutting remove all of the sections and let them fall into the bowl. Some of them will need a helping hand, so just give them a tug. Once all of the sections are out I usually give the remaining wad of membrane a squeeze to get out the remaining juice. This gives your sections something to swim around in and will keep them from drying out.
So that is it. When I do this I generally do a bunch at a time since it can get a little messy. The fruit will stay good in the refrigerator for a couple days at least. I wouldn't recommend freezing it though. I enjoy sectioned grapefruit as a refreshing snack while watching a movie or playing on E2. Enjoy.
Ouroboros has pointed out that anthropod has an excellent node on the pomelo in which he mentions the fact that pomelos are much easier to section than most other citrus fruit. You should head on over there if you have a pomelo that you just don't know how to deal with.