In this study (purchase required, US$ 24.95) the authors applied Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (AP-MALDI-MS) to assess the authenticity of ground black pepper samples using a non-targeted approach. MALDI is a mass spectrometry ionisation technique where the sample can be applied directly or with little preparation, and is often used for the analysis large molecules such as proteins and peptides.
A total of 58 samples, including authentic black pepper, adulterated pepper, and pure adulterants, were analyzed. Details of these training sets are not included in the open access abstract, nor the validation sets. The authors report that the AP-MALDI source was coupled to a linear ion trap mass spectrometer, enabling tentative metabolite identification. Spectral fingerprints revealed diagnostic ions including piperine, dimeric alkaloids, plant-specific flavonoid glycosides, and triacylglycerols.
The analytical performance of the method was evaluated using multivariate statistics (principal component analysis, PCA, and partial least squared discriminant analysis, PLS-DA) and two machine learning models were built: Random Forest (RF) and least absolute shrinkage and selection operator (LASSO). They report that Random Forest achieved the highest performance with 91.8% area under the curve (AUC) in cross-validation, 81.71% on the withheld test set and 85.0% accuracy on the test set.
The authors conclude that these results support AP-MALDI-MS as a robust, high-throughput approach for ground black pepper authentication, and demonstrate its applicability for screening spice authenticity with minimal sample preparation.
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