IO 
Journal of Agricultural Research 
Vol. It No. i 
organism that the latter method of study has been adopted as affording 
a truer picture of what the mold actually accomplishes in a ripening 
cheese. 
Penicillium roqueforti was grown upon ioo c. c. of Czapek’s solution in 
which cane sugar was replaced by 3 grams of fresh, filtered milk fat. 
After 50 days at about 23 0 C. dilute sulphuric acid was added to the 
culture until a blue color with Congo red was produced. The solids con¬ 
sisting of fat and mold mycelium were filtered off, washed with hot water, 
dried at ioo° C., and extracted over anhydrous copper sulphate with 
ether in a Soxhlet extractor. The fat of the ether extract was examined 
and gave the results shown in Table VI. 
Table) VI .—The effect of the growth of mold on the composition of milk fat. 
Condition. 
Age. 
Reichert- 
Meissl number 
for 2.5 grams. 
Acid number 
for 10 grams in 
decinormal c. c. 
Molecular 
weight of 
insoluble 
nonvolatile 
acids. 
Uninoculated. 
Days. 
50 
15- 87 
3. 20 
267. 6 
Inoculated. 
50 
1 5 - 66 
157 * 40 
271. 7 
1 Determination made on 1,8688 grams and calculated for 2.5 grams. 
The above data show that the fat of the uninoculated control gave 
constants typical of normal milk fat and consequently had undergone no 
changes, while the fat upon which Penicillium roqueforti had grown had 
been about two-thirds hydrolyzed. The filtrate from the culture con¬ 
tained no volatile acids, which would indicate that the soluble acids of the 
decomposed fat are consumed completely by the mold, while the insoluble 
acids are much less readily consumed. That other molds attack the 
fatty acids of low molecular weight more readily than those of higher 
molecular weight has been demonstrated by Laxa (9, p. 119). This 
explains the high acid number of the ether extract, for it is evident that 
if all the acids resulting from the hydrolysis of the fat were consumed, 
the ether extract of the mold culture would have been nearly neutral 
and would have shown the Reichert-Meissl number of normal milk fat. 
The conditions of food supply maintained in a Roquefort cheese would 
be more nearly simulated by growing the mold upon fresh curd than upon 
solids suspended in a liquid medium. Table VI shows the result of the 
action of the mold on the milk fat in such a culture. To 50 grams of 
fresh curd containing about 50 per cent of water 2 grams of sodium 
chlorid were added. (Roquefort cheese contains about 4 to 5 per cent of 
sodium chlorid.) The curd was sterilized and inoculated with Penicil¬ 
lium roqueforti and kept at about 23 0 C. On the dates designated the 
fat was separated by the Schmid-Bondzynski method and was examined. 
See Table VII. 
