183. — Growing yeast. With a glass rod, remove a drop of the sediment from growing yeast prepared as in Expt. 180. Place the drop on a slide, cover with a cover glass, and study as in the previous case. Remove some of the yeast found floating on the surface and study in the same way. Note that the yeast cells are in groups. Make a sketch of several groups, showing buds of various sizes. Note any other differences you can see between this growing yeast and the compressed yeast cake. 184. - - Effect of boiling. Prepare two test tubes of molasses and water and inoculate each with a drop of yeast. Plug with cotton. Place one test tube in water and boil for ten minutes, and then leave both test tubes side by side in a warm place for two days, and deter- mine whether the boiling has been sufficient to kill the yeast. 185. - - Wild yeast. Prepare several test tubes of molasses and water as described and without plugging with cotton leave exposed in various places for two or three days. Determine by the appear- ance of bubbles whether fermentation occurs. If any change takes place in the liquids, examine with a microscope to determine whether yeasts have found entrance from the air or whether some other micro- organisms are growing in the solutions. Commonly, bacteria will be found more abundant than yeasts. 186. - - Effect of age on yeast. Obtain an old sample of dried yeast cake. Prepare two tubes of molasses and water and inocu- late one with a small quantity of the old yeast cake and two others with a similar quantity of a fresh cake. Set aside in a warm place and determine in which fermentation starts sooner, and in which it 1 84 LABORATORY MANUAL OF FOODS AND COOKERY is the more vigorous. Examine with a microscope after fermenta- tion begins, to see if either contains other organisms besides yeast. 187. - - Action of yeast on bread. Mix up a little flour and water to about the consistency of dough for bread making and divide into three lots, A, B, and C. Into A and B place a little compressed yeast✪ Action of Yeast on Bread. A and B are then to be placed in a warm place for five or six hours, while C, without the yeast, is to be baked at once. After A and B have risen under the influence of the yeast, bake B at once in the oven, while A is to be thoroughly kneaded and then baked. Compare the results of A, B, and C, noticing the difference in the textures of the bread. 188. - - Over raising. Mix another lot of dough with yeast in the same way and allow it to rise in a warm place for twelve hours or more. Test with litmus paper to see if it is acid. Bake and taste to see if it has become sour. 189. -- Repeat Expt. 187, comparing cold milk, scalded milk, and water as the liquid to be used in the dough. Note which dough sours first. 190. - - Bread raised by wild yeast. Put a small amount of salt in a little milk and then allow it to stand in a warm place until a froth appears. Mix it with flour to make a dough and set aside to rise. Does the dough rise as rapidly and as satisfactorily as when yeast is used? Does the baked dough have the same taste?

AI-modernized reading of the original text

183. — Growing yeast. With a glass rod, remove a drop of the sediment from growing yeast prepared as in Expt. 180. Place the drop on a slide, cover with a cover glass, and study as in the previous case. Remove some of the yeast found floating on the surface and study in the same way. Note that the yeast cells are in groups. Make a sketch of several groups, showing buds of various sizes. Note any other differences you can see between this growing yeast and the compressed yeast cake. 184. - - Effect of boiling. Prepare two test tubes of molasses and water and inoculate each with a drop of yeast. Plug with cotton. Place one test tube in water and boil for ten minutes, and then leave both test tubes side by side in a warm place for two days, and determine whether the boiling has been sufficient to kill the yeast. 185. - - Wild yeast. Prepare several test tubes of molasses and water as described and without plugging with cotton leave exposed in various places for two or three days. Determine by the appearance of bubbles whether fermentation occurs. If any change takes place in the liquids, examine with a microscope to determine whether yeasts have found entrance from the air or whether some other microorganisms are growing in the solutions. Commonly, bacteria will be found more abundant than yeasts. 186. - - Effect of age on yeast. Obtain an old sample of dried yeast cake. Prepare two tubes of molasses and water and inoculate one with a small quantity of the old yeast cake and two others with a similar quantity of a fresh cake. Set aside in a warm place and determine in which fermentation starts sooner, and in which it is the more vigorous. Examine with a microscope after fermentation begins, to see if either contains other organisms besides yeast. 187. - - Action of yeast on bread. Mix up a little flour and water to about the consistency of dough for bread making and divide into three lots, A, B, and C. Into A and B place a little compressed yeast. A and B are then to be placed in a warm place for five or six hours, while C, without the yeast, is to be baked at once. After A and B have risen under the influence of the yeast, bake B at once in the oven, while A is to be thoroughly kneaded and then baked. Compare the results of A, B, and C, noticing the difference in the textures of the bread. 188. - - Over raising. Mix another lot of dough with yeast in the same way and allow it to rise in a warm place for twelve hours or more. Test with litmus paper to see if it is acid. Bake and taste to see if it has become sour. 189. -- Repeat Expt. 187, comparing cold milk, scalded milk, and water as the liquid to be used in the dough. Note which dough sours first. 190. - - Bread raised by wild yeast. Put a small amount of salt in a little milk and then allow it to stand in a warm place until a froth appears. Mix it with flour to make a dough and set aside to rise. Does the dough rise as rapidly and as satisfactorily as when yeast is used? Does the baked dough have the same taste?

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Action of Yeast on Bread

A laboratory manual of foods and cookery