Location: Sugarbeet and Bean ResearchTitle: Determination of sucrose content in sugar beet by portable visible and near-infrared spectroscopy Author
Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2014
Publication Date: 6/29/2014
Citation: Pan, L., Zhu, Q., Lu, R., McGrath, J.M. 2014. Determination of sucrose content in sugar beet by portable visible and near-infrared spectroscopy. Food Chemistry. DOI: 10.1016/j.foodchem.2014.06.117. Interpretive Summary: Sucrose yield is the most important trait in production of beet. Accurate measurement of the sucrose content of beets can be valuable in early selection and breeding of high sucrose-yield beet germplasm, proper timing of harvest, and postharvest storage and processing of beets. Currently, sucrose measurements are done using destructive methods at the sugar processing factory or in the research laboratory. This research was aimed at evaluating the feasibility of using two portable spectrometers, covering the visible and shortwave near-infrared (Vis/SWNIR) region of 400-1,100 nm and the near-infrared (NIR) region of 900-1,600 nm respectively, for measuring sucrose content from sugar beets. Spectral measurements were first made for 396 intact beets harvested from an experimental field of Michigan State University’s Saginaw Valley Research and Extension Center in Frankenmuth, MI in 2012, and then from sliced beets. The sugar content of the beet samples was measured using a wet lab chemistry analysis method. Mathematical models relating the spectral data to the sucrose content of beets were developed and then tested with the independent sets of samples. Relatively good predictions of sucrose content for the sliced beet samples were obtained with the correlation coefficients of 0.89 and 0.91 for the Vis/SWNIR and NIR spectrometers, respectively. Lower correlations were obtained for intact beets by both spectrometers. This research also identified wavelengths that had the most important contributions to the prediction of sucrose content. These wavelengths will be useful in further developing a spectroscopic method for sucrose prediction. The research demonstrated that spectroscopic measurement has potential for fast assessment of sucrose content of beets. However, further improvements in spectral acquisition and analysis are needed in order to achieve reliable and more accurate measurement of sucrose content for beets.
Technical Abstract: The feasibility of visible and near-infrared spectroscopy for measurement of the sucrose content of sugar beet was investigated with two portable spectrometers that cover the spectral regions of 400-1,100 nm and 900-1,600 nm, respectively. Spectra in interactance mode were collected first from 398 intact beet samples and then sliced samples. The sucrose content of beet samples was measured using high-performance liquid chromatography (HPLC). Calibration models for sucrose prediction were developed, using partial least squares, for both intact and sliced beets for each spectrometer. The spectrometer covering the region of 400-1,100 nm had the correlations of prediction (r) of 0.80 and 0.89, the standard error of prediction (SEP) of 0.89% and 0.68%, and the ratio of sample standard deviation to standard error of prediction (RPD) of 1.69 and 2.13 for intact beets and beet slices, respectively. The spectrometer with the spectral region of 900-1,600 nm had the r values of 0.74 and 0. 91, the SEP of 1.02% and 0.62%, and the RPD of 1.47 and 2.14 for intact beets and beet slices, respectively. These results showed that the portable spectrometers operated in interactance mode are potentially useful for predicting the sucrose content of beet slices. Through single wavelengths correlation analyses, this research also identified important wavelengths and/or spectral regions that had relatively strong correlation with the sucrose content. These wavelengths can be useful in further development of spectroscopic technique for beet sucrose prediction.