Raman Analysis of Natural Pigments During the Ripening Process in Different Types of Peppers

In this work, Raman spectroscopy was employed to identify compounds present in different ripening stages of various exocarp varieties of peppers from the Solanaceae family, pink peppercorns (Anacardiceae), and black and white peppercorns (Piperaceae). In situ analysis of Solanaceae peppers revealed the characteristic bands of phenolic compounds, carotenoids, fatty acids, and alkaloids such as capsaicin. In the malagueta peppers, habanero, “biquinho”, and red karneval, a shift of the ν(C=C) stretching bands of carotenoids to lower wavenumbers and an increase in the band intensity were observed during ripening. In pink peppercorns, analyses of the peel and seeds at different ripening stages did not show significant changes. However, bands attributed to anthocyanins, such as pelargonidin, were observed, suggesting that these flavonoids are responsible for the color of the peel. Analyses of black and white peppercorns revealed characteristic bands mainly attributed to piperine. The assignment of Raman bands was proposed through comparison with literature data and spectra obtained by the Density Functional Theory (DFT) method. The sum of the theoretical spectra was used to simulate the spectral profile and the contribution of each substance in the experimentalspectra.