Feasibility of using Raman spectroscopy for detection of tannin changes in pomegranate fruits during maturity

Abstract

Detecting changes in tannin as a major phytochemical content of pomegranate fruit can be used to monitor its maturity. In this study, using Raman spectroscopy as a rapid and noninvasive technique to distinguish four different maturity stages of pomegranate fruits (Immature stage (S1), Fairly Half-ripe stage: (S2), Half-ripe stage (S3) and Full ripe stage (S4)) on the basis of tannin changes was studied. Spectral acquisitions from fruit cross-sections in the wavelength range of 100-3000 cm−1 were carried out. A modified polynomial was fitted to the signals to remove the background and obtain desired peaks. Also, Self-modeling Mixture Analysis (SMA(was used to extract Raman signatures of different compositions from corrected spectra. After extracting of the pure component spectra using SMA from all the pomegranate fruit samples, the Spectral Information Divergence (SID) was performed to evaluate the degree of maturity of the pomegranate fruits. It concluded that Raman spectroscopy has a potential of the future development of a Raman-based nondestructive approach for subsurface detection of tannin as an indicator of pomegranate maturity.