| Summary: | <p>The objective of this study was to determine whether near
infrared reflectance spectroscopy (NIRS) could be effectively
used to determine the protein and tannin content of sorghum. In
addition, tannin content of whole and progressively dehulled
sorghum grain was predicted using NIRS.</p>
<p>The protein content of sorghum grain grown in 1983/84 and
1984/85 was analyzed by the Kjeldahl method and ranged from 7.4
to 16.7% and 8.4 to 15.1%, respectively. Tannin content was
analyzed using five different methods; vanillin hydrochloric acid
assay with an extraction time of 24 hr (V-HCl/24 hr), V-HCl/20
min, modified vanillin hydrochloric acid assay with an extraction
time of 24 hr (MV-HCl/24 hr), MV-HCl/20 min, and Prussian blue
assay with an extraction time of 10 min (PB/10 min). The
correlation coefficients between the methods for tannin analysis
ranged from 0.94 to 0.99.</p>
<p>Protein content of sorghum grain was predicted with
reasonable accuracy using NIRS. The standard error of prediction
corrected for machine bias (SEPc) 0. 43%, ratio of range/SEPc
(20. 8), and correlation coefficient (r) between the protein
content analyzed by the Kjeldahl method and protein content
predicted by NIRS was 0.99 (p < 0.01, n = 28) for the 1983/84
crop year; while the values for the 1984/85 crop year were SEPc
(0.28%), ratio of range/SEPc (16.5) and r = 0.99 (p < 0.01, n = 20) . It was found that when the 1983/84 prediction equation was
used to predict protein content in the 1984/85 crop year the SEPc
was 0.35%, range/SEPc was 13.8, and r was 0.98 (p < 0.01, n = 20) while when the 1984/85 prediction equation was applied to the
sorghum lines grown in 1983/84 the SEPc was 0.75%, range/SEPc was
12.4 and r was 0.99 (p < 0.01, n = 28).</p>
<p>The SEPc and range/SEPc for the whole sorghum grain was 3.54%
and 2.82, respectively. The correlation coefficient (0.66, p <
0.01, n = 20) between the V-HCl/24 hr assay and the NIRS method
was low but significant. The technique appears not to be suitable
for tannin analysis in whole sorghum grain. The correlation
coefficient between tannin values obtained by five different
assays and the NIRS method were 0.93, 0.91, 0.91, 0.86 and 0.86
for the V-HCl/24 hr, V-HCl/20 min, MV-HCl/24 hr, MV-HCl/20 min
and PB/10 min, respectively; the SEPc were 1.44, 1.09, 0.67, 0.86
and 0.16% while the range/SEPc were 6.72, 6.74, 10.0, 9.84 and
7.75, respectively. The tannin content of sorghum lines with a
narrow range of tannin (0 to 5%) was poorly predicted by NIRS
with a correlation coefficient of 0.61 (p < 0.01, n = 20). The
SEPc and range/SEPc was 1.32% and 3.55, respectively.</p>
<p>Tannin content of two progressively dehulled sorghum lines
was predicted with reasonable accuracy using NIRS. The SEPc was
0.11, range/SEPc was 19.1 and correlation coefficient between
the tannin values obtained by the V-HCl/24 hr assay and those
obtained by NIRS was r = 0.99 (p < 0.01, n = 20) for sorghum line
IS9487 while sorghum line IS9613 gave a SEPc of 0 .35%,
range/SEPc of 11.3 and a correlation coefficient of 0. 95 (p <
0.01, n = 26).</p>
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