Molasses

Crystallisation works because sucrose leaving a solution builds an orderly lattice that excludes other substances. That same selectivity is what eventually defeats the process: as the liquor concentrates, the non-sugars it contains rise in proportion, and they hold the remaining sucrose in solution and interfere with the crystals forming. The mill can push further — more boiling, more time, more energy — but each additional stage returns less, and there is a point where it is not worth it.

Molasses is therefore an economic boundary made visible. Where a mill draws the line is an operating choice, which is why the volume and the sugar content of a factory’s molasses are inversely related to how hard it drove its sugar recovery. The two streams are joined: less molasses generally means more sugar, and molasses richer in sugar generally means a mill that stopped earlier.

Every major use of molasses exploits the sugars the mill could not crystallise. Fermentation is the largest: yeasts do not care whether their sugar arrived in a crystal lattice or a syrup, so molasses feeds ethanol production, potable distilling — rum is by definition a cane spirit, and much of it is fermented from molasses — baker’s yeast, and a range of industrial fermentations producing acids, amino acids, and other chemicals.

• Fermentation — ethanol for fuel and industry
• Distilling — rum and other potable spirits
• Yeast production — baker’s and other yeasts
• Animal feed — as an energy source, a palatability enhancer, and a binder in compound feeds and blocks
• Industrial fermentations — organic acids, amino acids, and other products

In feed, molasses does several jobs at once: it supplies fermentable energy, it makes an otherwise dull ration attractive, it binds dust in a mix, and it acts as a carrier for supplements. It is sprayed onto compound feeds, mixed into rations, and cast into licking blocks for grazing animals.

Molasses is bought analytically. Total sugars is the primary term, since that is what both feeders and fermenters are paying for; Brix describes the dissolved solids concentration, and ash, sulphated ash, and unfermentable content matter to particular users. Fermenters care about things feeders do not, notably anything inhibitory to yeast, and a molasses that is good for one market can be poor for the other.

Handling is a liquid-logistics problem. Molasses is dense and extremely viscous, and its viscosity falls sharply with temperature, so tanks, lines, and road and ship tankers are designed and sometimes heated with that in mind — cold molasses simply will not move at a useful rate. It is stored in bulk tanks, and it is not inert in them: micro-organisms can act on the sugars, generating gas and heat, and stored molasses is monitored accordingly. Concentration is itself the main preservative, and molasses diluted by water ingress spoils far more readily than molasses kept at strength.