Propolis authentication of stingless bees by mid-infrared spectroscopy and chemometric analysis

Although stingless bees are widespread in tropical and subtropical regions worldwide, their by-products, including propolis, are rarely used. In this study, we aimed to chemically analyze and investigate the potential of mid-infrared (MIR) spectroscopy and chemometric analyses for the authentication of propolis. The content of phenolic compounds and total flavonoids were used as quality parameters according to the guidelines of the Brazilian legislation. Attenuated total reflection-infrared (ATR-IR) spectroscopy was performed, and a chemometric model was developed and validated to discriminate and classify the four samples of propolis. The partial least squares-discriminant analysis (PLS-DA) model was found to be sensitive, specific, and accurate, and can be used for the quality control of these propolis samples for authentication purposes. Plebeia propolis showed the lowest total phenolic and flavonoid content. As suggested by the ATR-IR and confirmed by the determination of total phenolics and flavonoids, only green, tubuna, and mandaçaia propolis met the criteria established by the Brazilian legislation for marketing. In conclusion, the infrared chemometric model developed in this study can be implemented as a tool for the authentication of the studied propolis classes.