Modeling Tomato Ripening Based on Carotenoid Raman Spectroscopy: Experimental Versus Kinetic Model

Abstract

This work reports on a combined experimental and theoretical investigation on the carotenoid Raman signal in several tomato fruits during their postharvest time evolution and ripening. Both resonant (180°) backscattering and polarized (90°) Raman scattering were used to monitor the most prominent bands of carotenoid (lycopene and β-carotene) evolution in different tomato varieties. Relevant findings of the present investigations were that while the depolarization ratio of the ν band hardly changed with time, the Raman ν band intensity did change showing a similar pattern for all tomatoes investigated. Indeed, all cases investigated revealed a rise of the carotenoid signal coincident with the onset of the turning stage of the fruit ripening, a pronounced maximum of the Raman signal followed by a post-maximum decline at the red ripening stage. A kinetic model has been developed to describe the time evolution of the observed Raman signatures based on the rate coefficient of the carotenoid synthesis and the time evolution of the scattering coefficient of the fruit. The model describes satisfactorily the tomato evolution through the distinct ripening stages providing new insight on the assessment of the postharvest fruit control and quality.

Raman Method in Identification of Species and Varieties, Assessment of Plant Maturity and Crop Quality—A Review

“…Martin et al [ 85 ] developed a tomato ripening model based on vibrational bands of carotenoids in Raman spectra. Tomato fruit during the growth phase and during the post-harvest ripening stage were analysed using a laboratory Raman spectrometer equipped with a 532 nm laser.…”

Raman-Based Diagnostics of Biotic and Abiotic Stresses in Plants. A Review

“…The work done by Nikbakht and co-workers also showed that RS can be highly effective in quality assessment of both external and internal properties of tomatoes (Nikbakht et al, 2011). Martin and co-workers further expanded the use of RS for the analysis of tomatoes ripening (Martin et al, 2017). The researchers developed a model of tomato ripening based on carotenoid vibrational bands in Raman spectra.…”

“…It has been found that an increase in carotenoid vibrations were coincident with the onset of the turning stage of the fruit ripening. The model built from the collected data describes the tomato ripening stages and helps to accurately assess postharvest fruit quality control (Martin et al, 2017).…”

A Four-Level Maturity Index for Hot Peppers (Capsicum annum) Using Non-Invasive Automated Mobile Raman Spectroscopy for On-Site Testing

“…Since the maturation process of tomatoes has been studied intensely [30,31,39], 30 hot peppers were compared to the same number of tomatoes. Each species was represented by 10 fruits of the categories immature, maturing and fully matured fruits, see Table 1.…”

“…Green or yellow harvested fruits also turn red when adequately stored and allowed to continue ripening. Since the degree of ripeness is related to the nutrients and to the carotenoid content, Raman spectroscopy is particularly suitable for monitoring of the process [29][30][31][32][33][34]. It provides good sensitivity to carotenoids and is non-invasive, such that the fruit can continue to evolve after analysis.…”