Book of American Baking / A Practical Guide Covering Various Branches of the Baking Industry, Including Cakes, Buns, and Pastry, Bread Making, Pie Baking, Etc.

by Various

A baked product if used as a nutriment must possess lightness and porosity and be so constituted that it can be easily digested.

For this reason yeast is required in bread making.

Yeast.

A Gas Test.—Dissolve in a flask 2 ounces of syrup or honey in a pint of water at 140 degrees F., and add one-sixth of an ounce of compressed yeast, which has been broken up and dissolved in a part of the saccharine infusion. Seal the flask with a perforated rubber cork, pass a bent glass tube through the perforation and attach a piece of rubber hose to the glass tubing. In fifteen or twenty minutes small bubbles will be seen rising to the surface of the fluid, which will continually increase in number, until the surface is covered with a froth formation, somewhat like the head of a cauliflower.

The fluid is fermenting.—After 1 to 1½ hours the froth forming gradually ceases and finally drops.

During fermentation lead the rubber hose attached to the generating flask into a smaller flask half filled with water. You will notice bubbles oozing from the mouth of the hose through the water. Then at once make a test by holding a lighted match into the small flask. The match will burn readily, just as it would in the air. After ten or fifteen minutes repeat this procedure and the burning match will be extinguished at once, even to the glimmer.

During the first test atmospheric air only was contained in the small flask. It required a little time for the gas of the generating flask to displace the atmospheric air, as a result of which the lighted match went out at the second test.

Another peculiar phenomenon is noticeable in connection with this test. On top of the water in the open flask the developed gas remains stationary, but can be dispersed by an air current, either created by blowing or by waving the hand over the opening of the bottle.

If we then pour some clear lime water into another small bottle and allow some of the gas from the generating flask by means of the rubber tubing to flow into the same, we will find that, after withdrawing the hose, closing the bottle with the thumb and slightly shaking the contents, the lime water turns milky.