Visit to a Yeast Factory

CAPE TIMES - 1933, April 4

How an Essential Food and Health Product is Made

The homemaker who makes her family’s bread today has a much simpler task than had her mother before her, for the hazards of her bread-making have been almost entirely removed since she has been able to purchase her yeast, fresh and wholesome and concentrated, in tiny briquettes of an ounce weight, which permit her to make exact measurements of her flour and other ingredients. All the compressed moist yeast which is used in the Cape Province and South West Africa is manufactured in the Cape Peninsula, under the most hygienic conditions.

In long lime-washed vats, barley, which is found to be the most suitable grain for the purpose in this climate, is kept at definite temperatures which promote its gradual germination, a process which develops disease, a peculiar ferment which has the power of converting starch into dextrin and then into sugar, and which is essential to the production of malt.

SUMMER PROBLEM

Some difficulty is experienced during the warm months in maintaining the germinating barley at the correct temperature (from 16 to 22 degrees Centigrade), since too rapid sprouting result in a loss of malt. However, by a system of frequent washing – which helps also to prevent mould – and by means of air blown through at intervals, this difficulty is to a great extent overcome. From the vats, the barley is conveyed to a huge crusher to facilitate the separation of the starch from the husks. The crushed malt is then piped into the malt tanks, great copper-lined vats, into which mealies, after being boiled for four hours at 2½ atmospheres, are then blown. Here the malt of the barley converts the starch of the mealies into sugar for fermentation.

Piped into a filter tank, the malt infusion is drawn off into two tanks, the strong wort tank and the fermentation wort tank. To the liquid in the latter, huge copper reservoirs about 18 feet in depth, concentrated “mother” yeast, which is imported from Denmark, is added. Compressed air, from a large electric plant, is forced continually through this mixture, to blow off the gases which are developed and to force the fermenting yeast to bud.

LENGTHY PROCESS

The process of fermenting takes about 13 hours, requiring microscopic and other tests, every hour, and the addition, from time to time of malt infusion from the strong wort tank. The utmost accuracy with regard to time, temperatures and strength of the various materials which compose this mixture is essential, and a well-equipped laboratory, in the charge of a qualified analytical chemist is maintained on the spot.

When the fermentation process is complete, the liquid is piped to powerful separators, exactly lie those used in creameries for separating the cream from the milk. The separated yeast passes over cooling pipes filled with chilled water into yet other copper tanks. The product now resembles thick cream.

This mixture is conveyed through pipes to an ingenious press composed of sections, in which the yeast, as the moisture is pressed out of it, builds up much as honey is build up in a comb.

From the presses, the yeast goes into a huge mixer, not unlike a churn, where it is thoroughly mixed, and then stamped tightly into large wooden casks and placed in a chill room maintained at a definite temperature until it is wanted for packing. At this stage, the product looks like pale butter and has a smooth pleasant taste of high-grade cream cheese. The slightly sour taste and distinctive flavor which we, who take yeast as a tonic and pick-me-up, notice in the yeast purchased in the shop, are due to the further development of lactic acid in the product.

This in no wise affects its value either as a food or a raising agent, but it is not recommended that yeast kept more than a couple of days, unless it is kept in a cool moist atmosphere, be used, if fresh yeast is obtainable.

When yeast is used daily by one or more members of the household as a tonic, if mechanical refrigeration is available, east may be purchased in one-half pound – 8 cubes – or one pound cartons. These should be placed in the hydrator or vegetable compartment, or else in a covered fruit bottle, as the dry air of the mechanical refrigerator tends to dry the yeast too much and to render it dark and unpalatable.

These cartons are now being stamped with the date they are supplied to the dealer, so that the purchaser need only ask to see the container to assure himself of the freshness, or otherwise, of the yeast he is buying.

Sarah Jampel writes more about yeast, one of the best single-celled microorganisms around. https://www.bonappetit.com/story/all-about-yeast