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Published online 1 January 1980
Published in Agron J 72:108-110 (1980)
© 1980 American Society of Agronomy
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Extractant Color as a Factor in Grain Sorghum Tannin Analysis1

M. K. El Tuhami, D. G. Cummins and R. E. Burns2

Methods of tannin analysis for sorghum [Sorghum bicolor (L.) Moench] depending on color reaction, such as vanillin hylrochloric acid (VHCl) and modified vanillin hydrochloric acid (MVHCl), have not accounted for the color of the extract due to various pigments before adding the test reagents. The objective of this study was to determine how much this original color intensity affects the apparent level of tannin in the plant material. Tannin in the extract was estimated by the traditional VHCl method. The original color of the extract (without reagents) was measured after adding methanol to the extractant and using methanol as 100% transmittance standard. The amount of tannin in the grain, milk, dough, and mature stages of 20 single cross sorghum hybiids was estimated. Results from the VHCl method compared to correction for extractant color showed that the original color of the extractant before adding the reagents for color development had a significant effect on the measured tannin levels. The amount of tannin measured after correcting for extractant color was significantly lower than that measured by VHCl. The corrected method showed that the amount of unmeasured pigments differed with maturity, location, hybrid, and year. The corrected method produced lower standard errors and coefficients of variation than the VHCl method, and the corrected method probably produced the most accurate estimation of astringent tannins.

Key Words: Sorghum bicolor (L.) Moench • Vanillin-HCl • Polyphenols • Leuco-anthocyanins

1 Contribution from the Univ. of Georgia Agric. Exp. Stn., Dep. of Agronomy, Georgia Station, Experiment, GA 30212. Part of thesis submitted by the senior author in partial fulfillment of the requirements for the Ph.D. degree at the Univ. of Georgia.

2 Graduate student, professor, and associate professor of agronomy. Present address of senior author: El Minia Univ., Faculty of Agriculture, Agronomy Dep., El Minia, Egypt.

Received for publication September 1, 1978.




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Copyright © 1980 by the American Society of Agronomy.