Effects of Waxy Types of a Sugarcane Stalk Surface on the Spectral Characteristics of Visible-Shortwave Near Infrared Measurement

Abstract

The precision of spectroscopic methods was frequently affected by the identity of the inhomogeneous materials, especially for direct scanning. This research aimed to investigate the effects of waxy types, naturally found on sugarcane surface, on spectral characteristics. A portable Vis/SWNIR instrument with interactance mode across wavelength of 570-1031 nm was used for direct scanning the cane stalk. Principal component analysis (PCA) was applied to examine the differences in the spectra scanned from 180 samples, including 3 types of waxy type: white, black, and mixed black and white. Seven widespread pretreatments were employed to reduce the effect of the waxy types. Results show that the spectra of the samples with each waxy type was separated in groups and standard normal variate (SNV) pretreatment gave the best results. However, it was not able to eliminate the effect compared to the wax-removed samples. Meanwhile, the standard deviation of absorbance values, at the wavelength of 760, 904 and 970 nm of 3 samples, was used for assessing the repeatability and reproducibility. The samples where the waxy covers were removed provided a lower standard deviation of absorbance values of spectra than the best pretreated spectra that used SNV of the samples that retained its waxy covers by one to six times. Thus, the waxy material on cane surface should be removed before collecting spectra.

Proximal spectroscopy sensing for sugarcane quality prediction and spatial variability mapping

“…The prediction results from SS samples for Fibre were close to those obtained for DF samples, as shown by the values of R 2 p and RPIQ. However, the results were less promising than those obtained by Phuphaphud et al (2019), which obtained the following results: maxima of 0.81 for R 2 p and 0.63 for RMSEP.…”

“…The spectral scan method on billets was adapted from and Nawi, Chen, and Jensen (2013) and Phuphaphud et al (2019). The spectral scans were performed at three equidistant points (around 120°) on the skin of each billet.…”

Evaluation of Minimum Preparation Sampling Strategies for Sugarcane Quality Prediction by vis-NIR Spectroscopy

“…However, several external factors must be considered to measure quality attributes by the SS method. A critical one is the constitution of the sugarcane skin itself, as various colors depending on the variety, black and white waxy material, and organic compounds may be present [ 24 , 46 ].…”

“…Improving the predicting performance of sugarcane quality parameters from billets for on-the-go systems may be possible [ 20 ]. Some effects, such as waxy and skin organic compounds, need to be considered and minimized [ 24 ]. Other data processing techniques such as nonlinear models [ 47 ] or advanced filtering methods such as orthogonalization [ 48 ], could be investigated to improve the performance aiming to develop reliable models for measuring sugarcane quality using billets of cane.…”

“…Furthermore, more recent studies have advanced with on-board vis-NIR spectroscopy sensor applications on the elevator of a sugarcane harvester simulator, i.e., analyzing samples at a distance and in motion [ 2 , 22 ]. However, Maraphum et al [ 23 ] and Phuphaphud et al [ 24 ] reported that the waxy material should be removed from the cane surface for maximum accuracy in the spectral data condition, even though this may be impractical for an embedded system. Associated with this fact, Phetpan et al [ 2 ] reported on the need to evaluate the potential of the vis-NIR spectroscopy technique with data sets consisting of a larger number of sugarcane varieties.…”