12 
BULLETIN 1305, U. S. DEPARTMENT OF AGRICULTURE 
The proteins in the kernels are a favorite medium for the growth of 
molds under certain conditions. Apparently the particular mold 
which grows on almond kernels and almond paste is Aspergillus 
repens. 2 Table 3 gives the results obtained from inoculating ground 
unroasted almond kernels of varying moisture content with the 
spores of this mold. 
Table 3. — Results of inoculating ground blanched almond kernels with spores of 
Aspergillus repens 
Sample 
Variety and character 
Moisture : Condition of mold after four weeks 
No. 1 
California Drake (had been blanched 
several weeks) . 
Same as sample No. 1, but with mois- 
ture restored in humidor. 
Per cent 
5.80 
9.61 
7.11 
6.81 
No. 2 
No. 3 
stage, indicating rapid growth. 
Molded more heavily than sample 
No. 1, but much less than sample 
No. 2. 
No. 4 
Portuguese (bitter taste and bitter- 
almond flavor) . 
From Table 3 it appears that in the first three samples the extent 
of the molding was in proportion to the moisture present in the 
kernels. Sample No. 4 did not mold, although it contained more 
moisture than sample No. 1. The reason for this is not apparent. 
The nuts used for sample No. 4 were bought in the open market 
under the name ''Portuguese." The kernels contain amygdalin, 
as evidenced by the fact that they develop a bitter-almond odor 
and taste when macerated with water. The ground kernels, how- 
ever, have no odor of bitter almonds. 
In view of the apparent relation of moisture content to the growth 
of this mold on almond kernels, tests were made to determine its 
relationship to the keeping quality of almond paste and almond 
powder. The results of these tests are given in Table 4. 
A study of Table 4 leads to the conclusion that moisture is quite 
necessary to the growth of Aspergillus repens in almond products. 
It will be noted especially that added moisture is much more con- 
ducive to its growth than moisture introduced with the kernels. 
Thus, samples Nos. 1 and 3 differ considerably in moisture content, 
but neither contained added water, and no mold growth was noted 
during the month of observation. All the samples to which water 
was added showed mold growth except No. 6, which was cooked 
and much of the added water removed. It seems logical to conclude, 
therefore, that almond powder which contains no added moisture 
should be entirely free from the growth of this mold. 
2 The writers hereby make acknowledgment of the helpful suggestions and assistance of Dr. Charles 
Thom and Miss M. B. Church, of the Mycological Laboratory, Bureau of Chemistry, in connection with 
the studies on the molds of almond products. 
