Prediction of Starch Content and Ethanol Yields of Sorghum Grain Using near Infrared Spectroscopy

Abstract

A rapid quantification method was developed and validated for non-destructive measurement of starch content, theoretical ethanol yield and actual ethanol yield of 48 cultivars of sorghum grain using Fourier transform near infrared (FT-NIR) spectroscopy in diffuse reflectance mode. Multiplicative scatter correction, Savitzky-Golay derivative smoothing and mean centring were used for processing the spectra of ground sorghum grain. The processed spectra were correlated with starch content, theoretical ethanol yield and ethanol produced through simultaneous saccharification and fermentation using partial least-squares regression (PLSR). The spectral range and number of factors were optimised for the low number of factors, high coefficients of determination for calibration (R 2 ) and validation (r 2 ), low root mean square error of prediction (RMSEP), high ratio of performance to deviation (RPD) and high ratio of the standard error of prediction to the range (RER). The best PLSR model for starch content utilised the 4000-6000 cm -1 wavebands and had the following values: R 2 = r 2 = 0.97, RMSEP = 5.5 g kg -1 grain, RPD = 5.9 and RER = 15. Likewise, the model for theoretical ethanol yield utilised the 4000-8000 cm -1 wavebands and had R 2 and r 2 values of >0.90, RMSEP = 4.9 g kg -1 grain, RPD = 4.47 and RER = 12.8. It was more difficult to predict actual ethanol yield using FT-NIR spectroscopy given the small data set, and spectra were collected prior to the fermentation step. Resulting PLSR models had R 2 and r 2 values of <0.60, RMSEP = 11.2-21.4 g kg -1 , RPD < 3 and RER < 6. These results demonstrated that FT-NIR spectroscopy may be a practical method for rough screening of sorghum cultivars for desirable starch content and theoretical ethanol yield. The models may be improved by including more cultivars in the model and additional compositional information, such as tannin and free amino nitrogen contents, in the chemometric analysis and using FT-NIR scans of the fermentation products to predict actual ethanol yields.

Evaluation of Carbohydrate Concentrations in Phalaenopsis Using Near-infrared Spectroscopy

“…The correlation between the spectra of Phalaenopsis powder and the carbohydrates was first assessed when selecting specific wavelength regions of the spectra. The absorption bands corresponding to carbohydrates have been reported in previous studies (Chang et al, 1998;Ghosh and Roy, 1988;Giangiacomo, 2006;Giangiacomo et al, 1981;Li et al, 2015;Rambla et al, 1997). The absorption band at 2270 nm was found to be suitable for estimating fructose, glucose, and sucrose (Chang et al, 1998).…”

“…Absorption bands near 1433,1520,1590,1730,1902,1950, and 2255 nm were correlated with glucose (Ghosh and Roy, 1988;Giangiacomo, 2006). Those close to 1433,1928,2254, and 2286 nm were correlated with sucrose (Giangiacomo, 2006;Giangiacomo et al, 1981;Rambla et al, 1997); however, those near 1678, 1735, and 1913 nm were correlated with starch (Li et al, 2015). Regarding the spectra with the best pretreatment parameters, the correlation coefficients of fructose, glucose, sucrose, and starch were distributed as shown in Fig.…”

An Investigation into the Possibility of Producing Fuel Ethanol from Forest Anchomanes (Anchomanes Difformis (Bl.) ENGL.)

“…Starch is a polymer of glucose. Although the starch content in tuber crops varies, it nevertheless serves as a predictor of ethanol yield (Li et al, 2015). To produce ethanol, the starch present in tuber crops would have to be hydrolysed into sugar, and the sugar fermented by yeasts.…”

“…The process performance was evaluated based on crude ethanol recovery per mass of substrate (kg-ethanol/kg-substrate). Ethanol recovery ratio was determined using Equation 8 after Li et al (Li et al, 2015). The basic fermentation equation is as stated in Equation 9.…”

“…This conversion was based on the assumption that 1 kg of starch completely hydrolysed would give 1.11 kg of glucose, and 1 kg of glucose would theoretically yield 0.511kg of crude ethanol (Li et al, 2015, Ocloo andAyernor, 2010), resulting into a maximum conversion efficiency of glucose to ethanol of 51.0 % on a weight basis. The value 1.11 is the theoretical conversion factor of starch to glucose (Li et al, 2015, Borglum, 1980. On the average, 1 t of fresh FA tubers would yield 74.2 kg of starch or 82.4 kg of glucose.…”