Refined Sugar

Refining begins by washing the raw crystal to take off the syrup film clinging to it — the affination step, and on its own a substantial purification, since much of what makes raw sugar impure is sitting on the outside of the crystal rather than inside it. The washed sugar is then dissolved, and the liquor is clarified and decolourised to remove the colouring matter and non-sugars that came through in solution. From that cleaned liquor sucrose is crystallised once more, and the crystals are spun off, dried, and screened to the grain the buyer wants.

What underlies all of it is the same principle that produced the raw crystal in the first place: a growing sucrose crystal excludes most of what is around it, so crystallisation is itself a purification. Refining is largely a matter of doing that again from a cleaner starting liquor, having removed by washing and decolourisation the impurities that a single crystallisation from cane juice could not exclude.

Raw sugar is centrifuged crystal that has been spun free of most of its mother liquor but not washed clean of it. It is deliberately unfinished, because a cane mill stops where it does for structural reasons: cane must be crushed close to where it grows, while the last stages of purification are a different business done at a different scale, usually near the people who will eat the sugar. Raw sugar exists because sugar has to travel, and it is the form in which it travels well.

Refined sugar is the other end of that journey. The colour that distinguishes the two is a coating and a contaminant load, not a property of the sucrose beneath it, so the difference between raw and refined is a difference in what has been taken away. That is also why they are handled so differently: raw sugar can be poured into a hold and grabbed out because it is going to be dissolved anyway, whereas refined sugar is bagged and protected, since anything it picks up defeats the point of having refined it.

Refining is not something done only to raw cane sugar. A sugar beet factory refines too — but it refines the juice, directly, as part of one continuous operation, and it does so without ever making a raw sugar. Beet juice purification is integral to the process rather than a stage bolted on afterwards: the juice is cleaned before it is evaporated, and the sugar that crystallises out of the cleaned syrup is already white. Roots go in one end of the factory and finished white sugar comes out the other.

The reason for the asymmetry is geography rather than chemistry. Beet grows in the temperate regions that consume the sugar, so there is no long haul between field and consumer to justify an intermediate product, and nothing is gained by stopping halfway. Cane grows in the tropics and much of its demand is elsewhere, so the industry splits in two — mills in the cane, refineries at the ports and near the markets — and raw sugar is what passes between them.

This is a distinction that is commonly missed, and missing it makes the sugar product tree look inconsistent. It is not: refined sugar sits downstream of raw sugar on the cane side, while on the beet side white sugar is the factory’s own primary product and is described here as beet sugar. Two routes, differently organised, converging on one product.

White sugar is bought on purity, colour, and grain. Colour is expressed in ICUMSA units — an internationally used scale on which a lower number means a whiter sugar — and what is required is set by the buyer and the contract rather than by any universal standard, because a soft drink maker, a baker, and a bulk industrial user are not asking for the same sugar. Grain size and uniformity, moisture, ash, and freedom from foreign matter complete the picture. Beyond a point these are all cleanliness measures, which is fitting for a product defined by what has been removed from it.

Sugar is hygroscopic and it cakes, so refined sugar is conditioned before it goes into a silo and the atmosphere around it is controlled — a silo of caked sugar is a serious problem to recover. It moves in bags, big bags, and bulk. And as with any fine dry organic solid handled in quantity, sugar dust is a recognised explosion hazard that handling systems are engineered around rather than an incidental housekeeping matter.