Method of making German yeast.—“This yeast in many distilleries forms an important by-product of the manufactory, and is collected and sold under the name of dry yeast, for the use of the private brewer and baker. When this is done, the process adopted is nearly as follows:—Crushed rye is mashed with the proper quantity of barley-malt, and the wort, when made, cooled to the proper temperature. For every hundred pounds of the crushed grain there are now added half a pound of carbonate of soda, and six ounces of oil of vitriol (sulphuric acid) diluted with much water, and the wort is then brought into fermentation by the addition of yeast. From the strongly-fermenting liquid the yeast is skimmed off, and strained through a hair-sieve into cold water, through which it is allowed to settle. It is afterwards washed with one or two waters, and finally pressed in cloth bags till it has the consistence of dough. It has a pleasant fruity smell, and in a cool place may be kept for two or three weeks. It then passes into a putrefying decomposition, acquires the odour of decaying cheese, and, like decaying cheese, has now the property of changing sugar into lactic acid, instead of into alcohol, as before. A hundred pounds of crushed grain will yield six to eight pounds of the pressed yeast. It is made largely at Rotterdam, and is imported thence to this country through Hull.”*
This is nearly the same process as the one pursued in Austria, and communicated recently by a correspondent of the Times. “Take brewery, or, by preference, distillery yeast, and filter it through muslin or a silk sieve into four or five times the quantity of water, which must be as cold as possible and in which, in summer, ice should be dissolved. Let the yeast and water be well stirred up together (in preference with a broom) until there is a good head of foam; then leave them until the yeast has settled and the water has become clear. Draw off the water gently without disturbing the yeast. (This is best effected by having a tub with taps in it placed at different heights, and by opening the highest first.) This done, again pump the tub full of fresh water, and stir the yeast up with it again. Repeat this until the water becomes tasteless and clear; then add to the settled substance, for every twelve gallons of yeast used at the commencement, half an ounce of carbonate of ammonia and one ounce of bi-carbonate of soda, previously dissolved in a pint of water. Mix this well with the purified yeast, and leave it for twelve or fourteen hours. Then again pump water to it, stir it up well, and, when once more settled, draw it off, which concludes the process. The yeast must next be turned into a linen bag, tied up, and placed between two boards large enough to cover it well, and very gently pressed to free it gradually from moisture, and convert it into a substance similar to bread-paste or dough, which can be formed to size and weight as needed.
“ In Austria the weight is something near one pound when dry, in square forms an inch thick.
“ The whole process should be conducted in a very cool place, and the yeast should be kept in a cold place, when it will remain good from eight to ten days in summer, and from ten to fifteen in winter.”
From this excellent receipt, which I have been obliged to curtail a little, it will be seen that German yeast is only common yeast thoroughly purified and rendered half-solid by pressure. It might easily be prepared in this country, either for sale or for domestic use, by the directions given above, which are very clear and ample.