10 
BULLETIN 79, HAWAII EXPERIMENT STATION 
gravity were made smaller in the solutions less than unity because of 
the greater concentration of kernels of normal composition in this 
narrow range. 
To divide a lot of kernels into specific-gravity groups, the kernels are 
first placed in the solution of specific gravity 1.000 and stirred vigor- 
ously to eliminate air bubbles. The kernels which float are skimmed 
off and the adhering solution removed by centrifuging. They are 
then placed in the 0.985 solution. Those which sink obviously have 
a specific gravity between 1 .000-0.985. In a similar manner the other 
separations are made so that a total of seven groups result from the 
six solutions, the heaviest group being that which sinks in the 1.100 
solution, and the lightest that which floats on the 0.970 solution. 
Table 4 shows the division into groups by this method and the rela- 
tion of these groups to roasting qualities. The percentages of oil 
corresponding to these specific gravities were taken from the values 
given in figure 1 . 
Table 4. — Relation of specific gravity of stnooth-shell-typc kernels to roasting 
qualities 
Specific 
gravity 
Proportion 
of oil in 
kernel 
Appearance of raw kernel 
Roasting qualities 
Percent 
>1. 100 
<50 
Small size, shriveled base, hard or 
Very dark color, unpleasant burnt 
tough texture, off color. 
flavor, hard texture. 
1. 100-1.050 
50 -61.5 
do 
Do. 
1. 050-1. 025 
61. 5-67 
do 
Do. 
1. 025-1. 000 
67 -72 
Slight shriveling of base; variable in 
Somewhat dark in color, tendency to 
size and color. 
off flavors and spongy texture. Sale- 
able, but distinctly inferior to lighter 
nuts. 
1. 000-0. 985 
72 -75 
Smooth base, plump, well filled, light 
Light golden color, mild nutty flavor, 
color. 
crisp texture, excellent. 
0. 985-0. 970 
75 -78.5 
do 
Do. 
<0. 970 
>78.5 
do 
Do. 
Table 4 shows the best grades of kernels to be those of a specific 
gravity of 1.000 or less. The group 1.000-1.025 is variable in flavor 
and texture. Repeated tests of kernels of both types at different 
seasons of the year and from a number of localities have resulted in 
the placing of this group in a distinctly lower price class for use 
possibly in the baking or confectionery trade or as nut butter. Kernels 
with a specific gravity greater than 1.025 appear to have little value 
except for vegetable oil or nut butter. There is no perceptible differ- 
ence in roasting qualities either as to flavor, texture, or color among 
the groups of specific gravity less than unity. 
On this basis, all kernels of a specific gravity less than 1.000 arc 
classed as grade 1; 1.000-1.025 as grade 2; and greater than 1.025 as 
culls. For practical purposes, it is thus possible to make all necessary 
separation with two solutions, namely 1.000 and 1.025 (pi. 4). 
Ordinary tap water at normal room temperature is sufficiently pure 
for use in commercial grading. This abbreviated method is now be- 
ing used commercially. It is more rapid and more accurate than 
hand separation of poor-grade kernels on the basis of the darker color 
and shriveled appearance after cooking. The expanded grading 
system is of value in the study of the differences in kernel quality in 
mils from individual trees. 
