It gets its name from the Demerara colony in Guyana, where this sugar was originally produced, but today it is mainly produced in Mauritius. It mostly consists of sucrose. There is also a type of demerara sugar which goes with the name London demerara sugar. This is nothing but refined sugar with added cane syrup.
Pressed sugar cane, that's separated from the bagasse is steamed to form thick cane syrup. It's then dehydrated at 150°C to form large golden brown crystals of sugar. It may be subjected to recrystallization if more refined product is desired. Since the sugar is not refined, it contains a residue of molasses which produces a rich and creamy texture in foods.
Demerara Sugar vs. Brown Sugar
Often people have wondered, what is the difference between demerara and brown sugar? We have just seen what is demerara sugar, now we will see what is brown sugar, so that the distinction between the two will be clearer.
There is no regulation which dictates how much molasses needs to be added to refined sugar to make it either light brown or dark brown. However, most of the producers add about 3% molasses to make light brown sugar and 6% to make dark brown sugar.
To it sum up, to make this sugar bagasse or excess plant material is not removed, the juice is directly crystallized, but for making light or dark brown sugar, molasses are first removed to make white sugar and then added back to make brown sugar. This process does seem to be strange to me as well, but this is exactly how the sugar is made.
There are many demerara sugar recipes which you will come across. However, if you come across recipes which demand granulated sugar or caster sugar or confectioner's sugar, it is better to use those only.
Usage of demerara sugar can have a negative impact on the recipe and the texture of the dish. At the same time, this sugar will discolor meringues and other pale foods. Some people are of the opinion that the use of demerara sugar makes terrible caramels.
If you want to have molasses-like flavor for baking, then pure molasses can also be used, but remember to cut down on the total quantity of sugar, else the dish you prepare may turn out to be much sweeter than you had desired it to be.