For most of its history, sugar was an expensive luxury, its price driven up by labour-intensive production methods and the need for tropical plantations. The sugar itself was coarse by today's standards, usually taking the form of a solid light-brown cake. These less-refined sugars survive today in the form of speciality products like Demerara or turbinado sugar.
About Brown Sugars
Modern commercial granulated sugars, whether white or brown, are very pure forms of a complex sugar called sucrose. It is refined through from sugarcane or sugar beets, each of which is pressed mechanically to extract a liquid that is high in natural sugars, as well as various impurities. Pure sugar is precipitated in crystal form from this syrupy liquid, which retains most of the impurities and a great deal of sweetness. This syrup, known as molasses, can either be left on the crystals or mixed back into the crystals to make brown sugars.
Most cane sugar production is split into two processes. The growing areas operate factories that produce coarse unrefined sugar and several grades of molasses, while refineries in industrialised sugar-consuming countries take the unrefined sugar and process it into market form. Raw sugars were originally known as factory sugars, meaning they were the less-refined product as manufactured in the sugar-producing regions. Rather than remove all the crystallising syrup for molasses, a portion of it was left on the crystals. This sugar was pale golden from the impurities, which included cane residue and some natural moulds.
Demerara sugar was originally manufactured and shipped from the port of Demerara, in British Guyana. It comes in the form of large, pale golden crystals, slightly sticky to the touch. Its flavour is light and delicate, less intrusive than the taste of conventional brown sugar in many applications. It is often used to sweeten coffee or tea, for example, where a distinct molasses note would be unwelcome. Many desserts call for it, especially in British cookbooks. Demerara sugar is also commonly used in mixing drinks, most notably hot rum drinks.
Turbinado sugar is very similar in most respects to the Demerara-style product. There are two discernible differences between them. Turbinado sugar is sold in slightly finer crystals than Demerara, although it is still coarser than conventional white granulated sugar. It is also less sticky than Demerara, with its crystals having the same dry, free-flowing character as white sugar. Turbinado sugar is slightly refined by steaming away a portion of its molasses, which accounts for both of these characteristics. Both turbinado and Demerara-type sugars are most often produced by adding molasses to white sugar, rather than the traditional methods.