Avaliação da influência da temperatura em farinha de maca peruana (Lepidium meyeniiWalp) utilizando-se espectroscopia e quimiometria

Abstract

Peruvian maca is a tuberous root grown mainly in Peru and in countries in South America. This plant has high nutritional values, which makes it commercially attractive. Generally, the maca is sold as a finely divided powder, making the product (flour) liable to fraud, which ranges from the drying process to the addition of other flours or bran. The drying process can be carried out in two different ways, by oven and by exposure to the sun, so that the product is influenced by this processing. To distinguish between the products, one possibility would be the use of the mid-infrared spectroscopy (MIR) technique, which works in the spectral region that varies between 4000 to 400 cm-1, allowing for quick and non-invasive analysis. When the obtained spectra are investigated using chemometric tools for pattern recognition purposes, such as Principal Component Analysis (PCA), or for discrimination, as in the case ofPartial Least Squares with Discriminant Analysis (PLS -DA), it is possible to compare many variables at the same time, allowing the evaluation of different samples regarding their compositions, which consequently enables the detection of adulterations. Therefore, the main objective of this study was to evaluate peruvian maca flours produced using different drying techniques, using MIR spectroscopy and chemometrics. In the study, the samples were evaluated by MIR spectroscopy, being the spectra evaluated by PCA and PLS-DA. The PCA did not allow differentiation between the samples. PLS-DA, on the other hand, discriminated the samples, allowing the construction of a discriminatory model with sensitivity 1.00and specificity 0.98. From the evaluation of the variable importance in projection (VIP scores), it was possible to infer that the main difference between the samples is related to substances derived from nitrogen. However, the identification of differentiating substances requires more informative analytical techniques, such as nuclear magnetic resonance and or mass spectrometry, which should be performed in future studies.