This section is from the book "Alcohol, Its Production, Properties, Chemistry, And Industrial Applications", by Charles Simmonds. Also available from Amazon: Alcohol: Its Production, Properties, Chemistry, And Industrial Applications.
In preparing beet molasses for fermentation, it is usual to sterilise them by slightly acidifying the diluted molasses, and boiling the solution. A portion is withdrawn after cooling, partly fermented with yeast, and returned to the bulk with the now-increased amount of yeast to complete the main fermentation. As the molasses themselves are poor in yeast-food, it is the practice to add a little maltopeptone or saccharified maize, or other nutrient substance.
1 K. Antal, Zeitsch. Spiritusind,, 1911, 34, 239, 252.
Cane-sugar molasses as used in this country are simply dissolved in water to make a wort of specific gravity about 1.030 to 1.040. In general, no preliminary inversion of the cane-sugar present is considered necessary, the action of the invertase of the yeast during fermentation being sufficient to invert the cane-sugar and render it fermentable. When a preliminary inversion is required, it is carried out by treatment of the diluted molasses with acid at boiling temperature for an hour, the acid being subsequently nearly neutralised before the fermentation is started. Alternatively, a special inversion operation with yeast may be carried out, at a temperature of about 50°.
In the tropics, juice expressed from the sugar-cane, and containing about 14 per cent, of sugar, is fermented directly. A wild yeast is found on the surface of the cane, and this sets up an active spontaneous fermentation when the juice is kept at a temperature of 30-35°. Nipa-palm juice is liable to contain a peroxydase, sometimes in sufficient quantity to destroy an appreciable proportion of the sugar, and the juice is therefore treated with a sulphite to reduce the peroxydase before fermentation. A wild yeast is also present in nipa-juice, and is used for the direct fermentation of the sap. In distilleries which employ both nipa juice and molasses, it is the practice to inoculate a portion of the diluted molasses with nipa juice to produce a ferment, which is then used for the fermentation of the main bulk.