POTATO SPIRIT. The use of the potato instead of grain as the source of supply of alcohol for commercial use has, during the past century, developed into an important industry, particularly in Germany where it is now a prominent feature in the organiza tion of the agriculture of the country. In great measure it is car ried on by the mutual co-operation of the farmers who supply to joint-owned distilleries the potatoes to be converted into alcohol, receiving later the spent wash and residues which are rich in nitrogenous matter and of considerable value as a cattle food. Extensive breeding of cattle is thus facilitated, resulting in a heavy production of manure useful in the cultivation of the po tatoes. In 1913 there were in Germany eight million acres of land devoted to potato cultivation. Three million tons of the crop were used for the manufacture of sixty-seven million gallons of alcohol, this representing about 8o% of the total alcoholic production of the country. In 1928 the industry had not recovered from the effects of the war, and in order to ensure that the supply of crops necessary for human and animal food should not be diverted to the production of alcohol, the price which might be paid for potatoes to be used for the latter purpose was restricted by the Government.
The underlying principle in the production of alcohol from po tatoes is the saccharification by means of malted barley or acids of the starch of which there is usually about 20%. One thousand
kilograms of potatoes produce spirit approximately equivalent to 74 litres of alcohol.
The details of the process show considerable variation. In one method extensively adopted the potatoes, after being cooked by steam heating and reduced to a homogeneous pulp in a mill, are mixed with malt and water. After the mass has been maintained at a temperature of about 60° C for 3-4 hours yeast is added and fermentation takes place. Distillation is accomplished by a process of steam heating, the mass being agitated meanwhile.
In another method the potatoes after being reduced to a pulp in a rasping machine are partially drained of their natural water. Boiling water and malt are added, the mass being allowed to stand for 3-4 hours. The clear liquid and subsequent washings are fer mented with yeast and the spirit distilled off in the usual manner. This method has considerable advantages over that first described, the distillation from the liquid being cleaner and the residual paste being excellent as a cattle food.
The spirit thus obtained by direct distillation is liable to act in a deleterious manner upon the animal economy. It has a strong odour and taste of fusel oil, amyl alcohol and isobutyl alcohol in particular being present in considerable proportion. This may be almost completely rectified by distillation in a patent still.