Yeasts for rum fermentations must be able to produce a high ethanol content and the correct aroma content. In small-scale production, especially in Jamaica, it is still common practice to rely on fermentation spontaneous resulting rums having a highly and individual flavour. In other cases pure cultures of yeasts are used. Fast-fermenting strains of Sacch. cerevisiae are pre ferred for light rums, but Schizosaccharomyces pombe is usually chosen for heavy rums. Molasses is the best source of yeast and can contain a wide range of genera including Candida, Hansenula Kloeckera, Pichia, Saccharomyces, Saccharomycodes, s saccharomyces and Torulopsis. Pure cultures of yeast are propa gated in molasses and inoculated at a high level of 4-10%.