At-line analysis of mill-prepared cane using near infra-red spectroscopy

Interest in near infra-red spectroscopic (NIS) analyses of mill-prepared cane has developed in recent years, but their feasibility has not been demonstrated beyond laboratory instrumentation. This research examined development of NIS analyses for mill-prepared cane using spectral data collected with an at-line, sample presentation module. Samples from Mulgrave and Tully mills in two seasons were spectrally analysed, and duplicate routine analyses conducted for basic quality components. The effects on NIS and routine analyses, of the addition of EM to clean cane, also were studied. Additional fibration of mill-prepared samples, unexpectedly, had little effect on spectral precision, possibly because of the high moisture content, and minimal benefits were evident in calibration development. Use of sub-sample, rather than mean subsample, spectral data little benefited calibration development. Additions of inorganic and organic EM to clean cane, surprisingly, had similar spectral effects, suggesting scattering may be a powerful physical influence. Instrument precision and sub-sampling related errors were minor. Calibration-related error could be large if sample numbers were small, or the samples do not adequately cover the complete range of near infra-red spectral properties encountered in practice. Prospects for global calibrations are good if the requirements for adequate sample numbers and coverage of spectral properties are met.