DEVELOPMENT OF RAPID METHODS FOR DETECTING SALMONELLA SPP. IN BLACK PEPPER BY SPECTROSCOPY AND CHEMOMETRICS

Black pepper (Piper nigrum L.) is one of the most economically significant spices, widely used throughout the world, which has earned it titles such as “Queen of Spices” and even “Black Gold.” Brazil occupies a prominent place in terms of production, being among the world's largest producers. However, due to the non-adoption of hygienic practices, microbiological contamination, marked by the presence of bacteria such as Salmonella, can result in significant problems that can compromise food safety. Thus, the present study aimed to develop rapid methods for detecting the presence of Salmonella spp. in black pepper samples using Near Infrared (NIR) and Mid Infrared (MIR) spectroscopy, associated with chemometric tools. For this research, 50 samples of black pepper, obtained in the form of grains from producers, spice shops, and bulk stores from different Brazilian states, were analyzed. The samples were ground for microbiological analysis to detect the presence or absence of Salmonella spp. using CompactDry SL plates, on which the samples were seeded according to the manufacturer's instructions. Next, NIR and MIR spectroscopic analyses were performed. The spectral data obtained were submitted to Principal Component Analysis (PCA) and Partial Least Squares Discriminant Analysis (PLS-DA). The results of the microbiological analysis showed that only five samples did not present the presence of Salmonella spp. The spectral data indicated, through PCA, a high capacity for dimensionality reduction, since more than 80% of the data variability was explained. The dispersion of the scores showed a tendency for separation of uncontaminated and contaminated samples. Finally, the analysis of the variables revealed that the regions around 2453 nm (NIR) and 2077 cm^-1 (MIR) were the most relevant for differentiation, corresponding to the peaks attributed to functional groups such as: C–H, O–H, C≡C and C=O stretches, respectively. The PLS-DA models, obtained using NIR and MIR, showed good distinction between classes, with 90% accuracy and low numbers of errors indicated by the confusion matrix, confirming the efficiency of the method for both techniques implemented. Thus, the study demonstrated the potential combination of NIR and MIR spectroscopic techniques with chemometric methods, making it a fast and effective alternative method for assessing the microbiological quality of black pepper.