Measurement of moisture, soluble solids, sucrose content and mechanical properties in sugar beet using portable visible and near-infrared spectroscopy

• Two portable spectrometers were used to predict compositions/properties of sugar beet.
• Good predictions of beet moisture, soluble solids and sucrose were obtained.
• Important wavelengths were identified for moisture, SSC and sucrose content prediction.
• Portable spectrometry is useful in production and processing of beets for sugar.

Visible and near-infrared spectroscopy, coupled with partial least squares regression, was used to predict the moisture, soluble solids and sucrose content and mechanical properties of sugar beet. Interactance spectra were acquired from both intact and sliced beets, using two portable spectrometers covering the spectral regions of 400–1100 nm and 900–1600 nm, respectively. Both visible and short-wave near-infrared (400–1100 nm) and near-infrared (900–1600 nm) spectrometers gave excellent predictions for the moisture, soluble solids and sucrose content of beet slices with the correlations (rp) of 0.89–0.95 and the standard errors of prediction (SEP) of 0.60–0.85. Lower prediction accuracies were obtained for intact beets, with the rp values of 0.75–0.85 and the SEPs of 0.88–1.23. However, the two spectrometers showed a poor ability of predicting the compressive mechanical properties (i.e., maximum force, area and the slope for the force/displacement curve) of both beet slices and intact beets. Using simple correlation analysis, we also identified wavelengths that had strong correlation with the measured compositions of sugar beets. The portable visible and near-infrared spectrometry is potentially useful for rapid assessment of the moisture, soluble solids and sucrose content of sugar beet at harvest and during postharvest handling and processing.