Table sugar is a molecule so stable it can sit dissolved for years
Sucrose, the stuff of white sugar, joins one glucose and one fructose through an unusual bond linking the reactive ends of both. That quirk makes it a non-reducing sugar, so a solution can sit for years almost unchanged, yet stomach acid or the enzyme sucrase splits it into its two halves quickly.
Its formula is C12H22O11. In most disaccharides the link runs from the reducing end of one sugar to a non-reducing part of the other, but in sucrose both reducing ends are tied up, leaving no anomeric hydroxyl group. That blocks further bonding to other sugars and stops sucrose from reacting spontaneously with proteins and other large molecules in cells and blood, as glucose does. Plants, algae and cyanobacteria make it, and no other organisms do; it is the end product of photosynthesis and a way for plants to store energy in roots, fruits and nectar.
The English chemist William Miller coined the word sucrose in 1857, from the French sucre plus the chemists' suffix for sugars, and Marcellin Berthelot introduced the now-obsolete saccharose in 1860. Many chemists tried and failed to build the molecule in the lab before Raymond Lemieux and George Huber managed it in 1953, starting from acetylated glucose and fructose.
Commercial sugar comes from cane or beet. Cane mills in the tropics crush the stalks and ship raw sugar elsewhere for refining, while beet factories in temperate regions turn out refined sugar directly. Refining involves washing the crystals, dissolving them, filtering the syrup and passing it over carbon to strip colour, then boiling it under vacuum until pure crystals form. Around 185 million tonnes were produced worldwide in 2017.
Pure crystals melt at about 189 degrees Celsius, although sucrose starts decomposing below that, which is exactly what cooks exploit to make caramel. Concentrated sulfuric acid strips out the water and leaves a black lump of carbon, and mixed with potassium nitrate, sucrose becomes rocket candy, a popular fuel for amateur rocket motors. Industry measures sugar solutions in degrees Brix, named after Adolf Brix: a 25 Brix solution is 25 percent sucrose by mass.
Source: Sucrose
