Revealing the chemical synergism in coloring tomatoes by Raman spectroscopy

In this work, Raman spectroscopy and DFT calculations have been used to identify pigments biosynthesized during the ripening of tomatoes. In situ analysis of the exocarp from tomatoes at six stages of maturation showed Raman bands attributed mainly to carotenes and flavonoids. The Raman spectra of the exocarp in earlier stages (green and breaker) are rich in carotenoids with nine conjugated double bonds, while later stages (light-red and red) are dominated by ones with 11 conjugated unsaturation. The Raman structural characterization of carotenoids biosynthesized from the phytoene, phytofluene, to beta-carotene is reported for the first time. Changes in carotenoid composition were observed along with the maturation; however, flavonoids/polyphenols that are concomitantly biosynthesized since the green stage presented the same spectral pattern along the process. Here, we present some clues based on Raman spectroscopy of the chemical synergism between carotenoids and flavonoids in coloring tomatoes.

Automated summary

In this study, Raman spectroscopy and DFT calculations were used to identify pigments biosynthesized during tomato ripening. The Raman spectra showed that carotenes and flavonoids are the main pigments in the tomato exocarp. The composition of carotenoids changed during maturation, while flavonoids/polyphenols remained constant. These findings provide insights into the chemical synergism between carotenoids and flavonoids in tomato coloring.