The most commonly used raw materials are cane juice, syrup and molasses. Cane juice is most suitable for manufacture of light rum and is prepared by pressing finely ground sugar cane. Cane juice can be fermented without further processing or, for higher quality rums, after heating and clarifying. Alternatively co syrup may be produced by vacuum concentration of cane juice. Molasses are used for production of rum with heavy aromas. Molasses is the mother liquor remaining after the separation of sugar from cane by repeated crystallization. The by-product of molasses that prices are relatively low and the product is of good keeping quality. Depending on the variety of cane, the growing climate and the means of production molasses contans 50-60% sugar.Molasses contains a number of compounds which contribute to the flavour of rum(see page 441) and also may contain inhibitors of yeast. Inhibitory substances include fatty acids and, in over heated molasses, hydroxymethylfurfural.