Deriving a grain hardness calibration for Southern and Western Cape ground wheat samples by means of the particle size index (PSI) method and Fourier transform near infrared (FT-NIR) spectroscopy

Abstract

The bread wheat hardness scenario among the Southern and Western Cape cultivars was investigated by deriving a FT-NIR hardness calibration for 198 ground bread wheat samples and using the particle size index (PSI) test as referencê method. Particle size index results indicate that the investigated bread wheat cultivars have a very wide hardness range of 37.05 - 60.50%. The influence of genotype, location, protein content and moisture content on wheat hardness was investigated by means of ANOVA, Student's t-test, correlation analysis and regression analysis. Significant differences (P < 0.05) in hardness were found for culitvars, while a positive linear relationship with protein content and a negative linear relationship with moisture content exist. The wheat samples were subsequently presented to the spectrophotometer in individual borosilicate-glass vials. A FT-NIR calibration was derived by performing a PLS regression on baseline-corrected spectra and the model was validated using an independent validation. Excellent results were achieved with an SEP, RMSEP and r of 2.13%, 4.53% and 0.89, respectively.