Rapid analysis of wheat flour by different handheld near-infrared spectrometers: A discussion of calibration model maintenance and performance comparison

Abstract

With the commercial availability of handheld near-infrared (NIR) spectrometers at significantly reduced costs, novel applications for qualitative and quantitative in-the-field and on-site analysis of such instruments for new user communities are currently reported. In the present study, the feasibility of rapid quantitative analysis of the essential quality parameters protein, wet gluten, moisture, ash, and sedimentation of wheat flour samples with three handheld NIR spectrometers based on different monochromator principles (Linear Variable Filter, Fourier-Transform Technique and Fabry-Perot Tunable Filter) has been investigated. In view of the long-term (two years) measurement and calibration schedule with reference sample batches of significantly varying parameter values, the necessary countermeasures for the important issue of calibration maintenance have been addressed and discussed in detail. Due to the variation of available reference values for the different flour parameters, the total number of reference samples varied between 124 (for sedimentation) and 235 (for moisture). These samples were then split up in a 3/1 calibration/test set ratio. Based on the detailed analysis of the statistical calibration parameters and the prediction accuracy for the test sample sets of the different flour parameters, the performance of the spectrometers under investigation has been compared. Despite instrumental and sampling deficiencies, such as hardware changes and significantly varying sample batches, respectively, during the long-term measurement schedule, the results proved the general suitability of the different handheld NIR spectrometers for the rapid quantitative on-site determination of the essential wheat flour parameters.