Vibrational Spectroscopic Evaluation of the Composition of Flax (Linum usitatissimum L.) Seeds: Differences for Cultivars

Flax (Linum usitatissimum L.) is a crop widely cultivated for fiber and oil production. The screening method for flax breeding must effectively address the biochemical characteristics of flaxseeds. In this study, to characterize flax cultivars, we extracted oil, defatted kernel, hull, and mucilage from whole seeds for the ATR-FT-MIR and FT-Raman spectroscopic measurements. In addition, for ATR-FT-MIR analysis, oil samples were obtained by pressing the flaxseed directly onto the crystal surface. After removing any seed residues, a grease stain was used for the measurement, allowing for the acquisition of the oil spectrum from a single seed. This method also enabled the detection of free fatty acids, serving as evidence of seed damage. Both methods effectively estimated the degree of unsaturation as a cultivar marker. The vibrational spectra of defatted kernels showed strong protein features; polysaccharide bands dominated in hull and mucilage spectra. Discrimination of flax cultivars using principal component analysis of vibrational spectra in specific regions was the most promising for flaxseed oil and mucilage. Multivariate analysis of a set of selected variables sensitive to the flaxseed oil composition successfully distinguished all flax cultivars of this study. The strong correlation observed between ATR-FT-MIR and FT-Raman results confirmed that these methods are comparable for characterizing different grades of flaxseed oil.