TESTING WHEAT FOR PROTEIN 
13 
were used, with wheat having a high, medium, and low protein con- 
tent. Samples from the hard red spring crop were chosen, as 
greater difficulty was experienced in obtaining uniform results from 
these samples. All samples were ground to pass through a No. 36 
grits-gauze sieve. As shown in Table 8, the time was varied from 
15 minutes to 2 hours in 15-minute intervals. Tests were run in 
triplicate and a blank determination was run as every tenth deter- 
mination. 
The digesting mixtures were as follows : 
Kjeldahl mixture, 20 cubic centimeters acid, 10 grains K 2 S0 4 , 0.7 
gram yellow HgO. 
Gunning mixture, 20 cubic centimeters acid, 10 grams Na 2 S0 4 , 
0.2 gram copper sulphate. 
Kansas City Protein Referee Board mixture, 20 cubic centimeters 
acid, 7 grams Na 2 S0 4 , 0.5 gram HgS0 4 , and 0.1 gram CuS0 4 . 
With the 1-gram sample, 20 cubic centimeters of acid was used 
throughout for the reasons given in the previous section. 
Referring now to Table 8, it was found at low heat that the 
Kjeldahl method was the only one which digested the samples 
completely in less than one hour. With this intensity of heat, 
the Gunning method was very inefficient. In fact, complete oxida- 
tion was not obtained in two hours with this method. It took 75 
minutes to digest the sample with the Kansas City Protein Referee 
Board method, whereas only an hour was required with the Kjeldahl 
method. 
Table 8. — Influence of time, method, and sample on protein test results 
KJELDAHL METHOD 
• 
Sample No. 
Time of digestion— minutes 
15 
30 
45 
60 
75 
90 
105 
120 
High heat: 
12004 
Per cent 
12.77 
15.28 
11.23 
12.65 
15.10 
11.17 
12. 61 
15. 12 
0) 
Per cent 
12.79 
15.33 
11.37 
12.71 
15.22 
11.29 
12.72 
15.18 
11.29 
Per cent 
12.85 
15.43 
11.40 
12.77 
15.28 
11.39 
12.84 
15.29 
11.34 
Per cent 
12.86 
15.45 
11.41 
12.88 
15.43 
11.39 
12.88 
15.45 
11.40 
Per cent 
12.88 
15.39 
11.40 
12.87 
15.42 
11.39 
12.88 
15.45 
11.42 
Per cent 
12.88 
15.40 
11.40 
12.87 
15.43 
11.39 
12.80 
15.45 
11.44 
Per cent 
12.88 
15.40 
11.42 
12.87 
15.44 
11.40 
12.88 
15.39 
11.43 
Per cent 
12.88 
12006 
15.40 
12008. 
11.43 
Medium heat: 
12004 
12.87 
12006- . 
15.42 
12008. „ -- 
11.40 
Low heat: 
12004-. 
12.88 
12006. . 
15.45 
12008 
11.40 
KANSAS CITY PROTEIN REFEREE BOARD METHOD 
High heat: 
12004 
12.65 
15. 20 
11.17 
12.48 
15.22 
C 1 ) 
0) 
0) 
0) 
12.70 
15.38 
11.37 
12.65 
15.38 
11.29 
12.48 
15.04 
11.19 
12.82 
15.38 
11.39 
12.82 
15.38 
11.34 
12.54 
14.98 
11.23 
12.82 
15.35 
11.40 
12.87 
15.39 
11.46 
12.77 
15.15 
11.29 
12.82 
15.38 
11.44 
12.88 
15.38 
11.41 
12.85 
15.38 
11.44 
12.82 
15.38 
11.44 
12.82 
15.38 
11.42 
12.82 
15.33 
11.40 
12.82 
15.35 
11.42 
12.85 
15.38 
11.44 
12.82 
15.38 
11.40 
12.82 
12006 
15.38 
12008 
11.40 
Medium heat: 
12004. 
12-82 
12006 
15.38 
12008- — 
11.40 
Low heat: 
12004- 
12.82 
12006 
15.40 
12008--. 
11.43 
Not clear. (See footnotes, p. 6.) 
