Sweet and sour
The sharp taste of grapefruit is especially welcome on dreary winter days. Grapefruit used to be very tart - so sour and acidic that some people sprinkled sugar over the fruit before eating it. It has since been selectively bred to be sweeter, although it still has an acidic bite.
For the most part, the grapefruit is considered healthy - it is high in fibre and some vitamins (especially vitamin C), and is much loved by dieters (there's even a weight-loss plan based around the fruit). If you are taking prescription medications, though, you should consult your doctor before consuming the fruit, because it can affect the potency of some drugs. Raw grapefruit, like fresh pineapple, contains an enzyme that prevents gelatin from 'setting', so if you are inclined to make jelly, you need to cook the fruit and juice before mixing it with the gelatin.
Like other types of citrus, such as lemon, orange and pomelo, grapefruit consists of small, juicy cells enveloped in a thin, white membrane.
The grapefruit's membrane is thicker and tougher than that of an orange, although thinner than a pomelo's, so it's usually not eaten; instead the fruit is often cut in half equatorially and the juicy flesh is spooned out.
A more elegant way of serving grapefruit is to supreme it: cut off the top and bottom, just far down enough to expose the flesh. Stand the fruit on one end and use a sharp, serrated knife to cut off the skin and a thin layer of the flesh from top to bottom, following the curve of the grapefruit. Hold the peeled fruit in one hand and cut between the membranes down towards the core, slicing out segments of the flesh from between the membrane. Squeeze the juice out of the remaining membrane before discarding it.
Grapefruit can be used in dishes in place of orange or lemon. For grapefruit curd, whisk together eggs, sugar and a little salt, then add grapefruit juice before whisking over a bain-marie. When the curd is thick, whisk in some finely grated grapefruit zest (this boosts the flavour) and chunks of cold, unsalted butter (which helps to cool the curd and give it a smooth, silky texture).