In the sorghum-growing regions of the United States, 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 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 near infrared spectrometer in the 950–1650 nm wavelength range. A partial least squares 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 of 3.91% predicted the sorghum content of an independent set of flour mixtures with r2 = 0.97, root mean square error of prediction = 5.25% and bias = −0.49%. Fourier-transform infrared spectroscopy 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 near infrared model had major peaks around overtone and combination bands of C–H stretch and bending vibrations at 1165, 1220, and 1350 nm. Therefore, the above results confirmed that sorghum content in corn sorghum flour mixtures can be determined using near infrared spectroscopy.

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近红外光谱法分析玉米高粱粉生物乙醇原料中的高粱含量

在美国的高粱种植区，一些生物乙醇工厂根据价格和供应情况使用玉米和高粱谷物的混合物作为原料。为了监管目的和优化乙醇制造过程，了解碾磨原料的谷物成分很重要。因此，开发了一种近红外光谱法来测定玉米-高粱粉混合物中的高粱含量。商业玉米和高粱谷物样品是在 18 个月内和两个作物季节从生物乙醇工厂获得的。制备了一系列含有 0-100% 高粱的玉米-高粱粉混合物，并使用近红外光谱仪在 950-1650 nm 波长范围内进行扫描。开发了偏最小二乘回归模型来估计面粉混合物中的高粱含量。R2 为 0.99 且交叉验证的均方根误差为 3.91% 的校准模型预测了一组独立面粉混合物的高粱含量，r2 = 0.97，预测的均方根误差 = 5.25% 且偏差 = -0.49% . 傅里叶变换红外光谱用于检查玉米和高粱粉的光谱差异。在 2930、2860、1710、1150、1078 和 988 cm-1 处观察到吸收差异，表明玉米和高粱粉的 C-H 反对称和对称、C=O 和 C-O 拉伸振动不同。近红外模型的回归系数在 1165、1220 和 1350 nm 处的泛音和 C-H 拉伸和弯曲振动的组合带附近具有主要峰值。所以，