Eragrostis tef (Zucc.) Trotter is an Ethiopian millet cereal that stands out for being gluten-free and for having high nutritional value, which makes its flour attractive for adulteration and demanding fast methods to fraud control. In this context, EDXRF is a promising spectroscopic method for enabling the analysis of mineral profiles by excitation with X-rays. In this work, EDXRF spectroscopy combined with ComDim-MLR was evaluated to quantify adulteration in teff flours. Brown teff flour was adulterated with rice, oat, whole wheat, and rye flours. Adulteration, with a maximum value of 35%, followed a simplex-lattice {5,4} mixture design, totaling 144 samples. EDXRF spectra were collected in a Shimadzu EDX 720 spectrophotometer with voltages of 15 kV to detect light elements and 50 kV for heavy elements. In MATLAB 2021a, the spectra (15 kV and 50 kV) were combined using COMDIM mid-level data fusion for feature extraction. Multiple least squares regression models were obtained between the common dimensions (CD) score matrix and the teff percentage in the evaluated samples. The samples were separated into calibration and prediction sets by the SPXY method and 8-fold cross-validation was employed to determine the number of CDs used in the model. The model with 4 CDs presented r2cal = 0.9478, RMSEC = 0.0391, RPDcal = 4.4001, r2cv = 0.9391, RMSECV = 0.0424, RPDcv = 4.0623, r2prev = 0.9065, RMSEP = 0.0245, and RPDprev 2.8444. The figures of merit demonstrate a good performance of the model, with high correlation and reduced error of prediction for unknown samples. Therefore, the EDXRF-COMDIM-MLR approach can be used in the quantification of adulterations in teff flour, and it can also be tested for other adulterations in high commercial value flours.

Acknowledgments: UTFPR, CAPES, CNPq e CAMulti-CM.