Two-Dimensional Correlation Analysis of near Infrared Spectral Intensity Variations of Ground Wheat

Abstract

Generalised two-dimensional (2D) correlation analysis was applied to characterise the NIR spectral intensity fluctuations among many spectra of ground wheat with multi-variable variations. Prior to 2D analysis, the spectra having neighbouring protein reference values were averaged and then the new spectral set was subjected to principal component analysis for cluster classification. This was repeated for sodium dodecyl sulphate sedimentation (SDSS) volume. Synchronous and asynchronous 2D correlation spectra enhanced spectral resolution and provided information about protein content- and SDSS index-dependent intensity changes not readily accessible from one-dimensional NIR spectra of wheat. The results revealed remarkable differences between the protein content- and SDSS index-induced NIR spectral response. Of interest were several unique protein bands around 1980 nm, 2040 nm, 2200 nm, 2260 nm and 2350 nm in high protein and SDSS wheat. At least one of these bands could be associated with gluten protein (a complex formed primarily from gliadin and glutenin) that influences the end-use quality of wheat flour.