ORANGE
Orange is a citrus fruit, along lemon, grapefruit, lime, and mandarine; and they have their seasonal peaks during winter. Citrus fruits come originally from Asia and have gradually spread all around the world to be grown in the warmer climates. Orange is possibly a cross between mandarin and pummelo that was accomplished long time ago. Oranges are interesting in that they contain not only the aromatic acidic flesh but also have a good amount of aromatic oils in their skin, which is therefore often used for enhancing flavors in dishes (orange zest), especially desserts. Not uncommon are the combinations of oranges and chocolates. The special character of this fruit that combines both sweetness and acidity makes it a nice complement to many other foods (see discussion below). Another good thing about oranges is their relatively long storage time, partially due to the tough skin and rind that protects them from microbes and mechanical damage. In short, oranges are maybe the most versatile citrus fruit you can use in cooking.
There are several types of oranges and they all have their unique characteristics. Navel oranges, so called after the navel-like shape of the bottom, are popular for eating fresh and for easy peeling, along with not having seeds. What they are not so good at is in the cooking, since their juice becomes very bitter shortly after it has been squeezed out of the fruit. In addition, the navel orange juice is maybe not the fruitiest one you can get from an orange.
Common oranges or juice oranges (see picture above) don't have the navel-like shape of the bottom, but they do have seeds and the skin is more difficult to peel. On the other hand, their juice is better and is not becoming that bitter after it has been squeezed out. The juice flavor can be further enhanced by the skin oils, just add some orange zest to it.
Blood oranges don't have the orange juice, but rather red one - hence the name. The red color is created by antioxidant molecules that are good for our health, and the juice taste is also more unique, sort of mix between common orange and berries.
To the less known sorts of oranges belong sour oranges, used mainly for marmelade production, and acidless oranges that just have a small fraction of the acidic notes in their juice.
Nutritionally speaking, oranges are famous for their high content of vitamin C - about 100 g/3 oz gives you the recommended daily intake. They are also packed with antioxidants, especially blood oranges. Dietary fibers in oranges are contained within the cell walls and rind, so you need to eat these segment lines and the white rind in order to get a slice of fibers in your diet. To some degree, oranges also contain some vitamin A and B1. Some studies have also shown the bad cholesterol-lowering effects of the orange zest.
When buying oranges, pick the ones with firm skin without any soft spots or mould. They don't have to be uniformly orange in color - many times, the color is chemically induced, so oranges with some green spots may be as good as the really orange ones. Oranges that weigh heavy are more juicy than the ones that feel more spongy, so pick the heavy ones.
If you are going to use orange zest, it is a good idea to wash the skin first (pesticides are often used on oranges, unless organically grown) and dry it. First then do the orange zest. It is common to also briefly cook the zest in boiling water to make it less bitter, then drying it on a paper towel.
Oranges can be used not only for desserts but also for other courses, like duck or chicken. If being the main ingredient, they can be complemented with liqueurs like Cointreau or Grand Marnier, and also Armagnac or Kirsch - all being sweet and acidic fruit liqueurs. Also other fruits like strawberries or mangoes, or other foods in this sweet and sour class may be experimented with. Spices like ginger, basil, vanilla, or cardamom can also be used succesfully with oranges.