216 YEASTS AND MOLDS 
II. Ascospores not known, 1.e., Fungi Imperfecti. 
Heavy dry pellicle formed on liquid media..... 8. Mycoderma 
No distinct pellicle formed: 
Vegetative cells forming a septate mycelium 
under exceptional conditions but predom- 
inately budding....... 0... ee. ee eee 9. Parasaccharomyces 
Vegetative cells formed only by budding. 
Cells apiculate, lmmoniform. .............. 10. Pseudosaccharomyces 
Cells frequently elongated into narrow non- 
septate hyphal threads ............... 11. Pseudomonilia 
Cells typically yeast-like................... 12. Cryptococcus 
Compressed Yeast. The greater part of the procedure in the 
manufacture of compressed yeast is concerned with the preparation of 
the medium or “‘ mash.” This is commonly prepared from a mixture 
of grains, rye, corn and barley being commonly used. After thorough 
cleaning, the barley is malted in the usual manner. The malt is later 
put into a kiln to stop germination. The mash is then prepared by 
mixing the ground grains with the malt and maintaining at a constant 
temperature of 60° until all of the starch has been changed to soluble 
sugars. The mash is then soured for two reasons. It renders the nitro- 
genous matter available to the yeasts and also prevents the changes 
induced by the putrefactive bacteria. The souring process is continued 
until about 1.5 per cent of acid has been produced. The mash is then 
passed through filter presses which gives a clear filtrate called the wort. 
This supplies the foods for the yeasts. It is inoculated either by a pure 
culture or a portion of the previous day’s run. An optimum tempera- 
ture is maintained during which there is a vigorous multiplication of 
the yeast cells. The cells are carefully filtered out and pressed into 
cakes with or without starch. The steps in the preparation of com- 
pressed yeast are graphically shown in Fig. 53. 
Yeast Foods. The use of these substances in bread making has 
been investigated by Kohman (1916) and his co-workers. The inves- 
tigation apparently had its origin in the effect of different natural 
waters on the yeast fermentation in bread as noticed by a large baking 
company. Kohman showed that by the use of small quantities of 
ammonium and calcium salts and potassium bromide brought about 
a saving of from 50 to 65 per cent in the usual amount of yeast. Other 
distinct advantages connected with the use of these nutriments are also 
noted. Hoffman (1917) in discussing the same subject has stated: 
“Since there is so much evidence in favor of all the ammonium chloride 
being changed to protein by the yeast, we can calculate how much protein we 
