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ARS Home » Plains Area » Manhattan, Kansas » Center for Grain and Animal Health Research » Grain Quality and Structure Research » Research » Publications at this Location » Publication #369808
Research Project: Impact of the Environment on Sorghum Grain Composition and Quality Traits

Location: Grain Quality and Structure Research

Title: Analysis of sorghum content in corn-sorghum flour bioethanol feedstock by near infrared spectroscopy

Author
item PEIRIS, KAMARANGA - Kansas State University
item Bean, Scott
item Tilley, Michael - Mike
item JAGADISH, KRISHNA - Kansas State University

Submitted to: Journal of Near Infrared Spectroscopy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2020
Publication Date: 6/20/2020
Citation: Peiris, K., Bean, S.R., Tilley, M., Jagadish, K. 2020. Analysis of sorghum content in corn-sorghum flour bioethanol feedstock by near infrared spectroscopy. Journal of Near Infrared Spectroscopy. https://doi.org/10.1177/0967033520924494.
DOI: https://doi.org/10.1177/0967033520924494

Interpretive Summary: In the sorghum growing regions of the U.S., some bioethanol plants use mixtures of corn and sorghum grains as feedstocks depending on price and availability. For regulatory purposes and for optimizing the ethanol manufacturing process, knowledge of the grain composition of the milled feedstock is important. It is not always possible for ethanol plants to source the same mixture of grains or to separate sorghum and corn as they are processed. Thus, a near infrared (NIR) spectroscopy method was developed to determine the content of sorghum in corn-sorghum flour mixtures to facilitate the use of sorghum in bioethanol production and assist ethanol plants in optimizing their production process. NIR was found to be able to predict the composition of corn-sorghum flour blends with an r-square of 0.97 and error of prediction of 5.25%. Thus, NIR is a valuable tool for use in ethanol plants to determine the composition of feedstock mixtures.

Technical Abstract: In the sorghum growing regions of the U.S., some bioethanol plants use mixtures of corn and sorghum grains as feedstocks depending on price and availability. For regulatory purposes and for optimizing the ethanol manufacturing process, knowledge of the grain composition of the milled feedstock is important. Thus, a near infrared (NIR) spectroscopy method was developed to determine the content of sorghum in corn-sorghum flour mixtures. Commercial corn and sorghum grain samples were obtained from a bioethanol plant over an 18- month period and across two crop seasons. An array of corn-sorghum flour mixtures having 0-100% sorghum was prepared and scanned using a NIR spectrometer in the 950-1650 nm wavelength range. A partial least square regression model was developed to estimate sorghum content in flour mixtures. A calibration model with R2 of 0.99 and a root mean square error of cross validation (RMSECV) of 3.91% predicted the sorghum content of an independent set of flour mixtures with R2 = 0.97, root mean square error of prediction (RMSEP) = 5.25% and Bias = -0.49%. Fourier-transform infrared spectroscopy (FTIR) was utilized to examine spectral differences in corn and sorghum flours. Differences in absorptions were observed at 2930, 2860, 1710, 1150, 1078, and 988 cm-1 suggesting that C-H antisymmetric and symmetric, C=O and C-O stretch vibrations of corn and sorghum flours differ. The regression coefficients of the NIR model had major peaks around 1165, 1220, and 1350 nm showing that NIR model had higher weights around overtone and combination bands of C-H vibrations suggesting that the NIR method is effective due to the differences in NIR absorptions of corn and sorghum flour.