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Chemical Shift Imaging of Spatial-Temporal Changes of Lycopene in Tomatoes During Ripening

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2010 Pittsburgh, Pennsylvania, June 20 - June 23, 2010  1009385.(doi:10.13031/2013.30030)
Authors:   Yu-Che Cheng, Tsu-Tsuen Wang, Jyh-Horng Chen, Ta-Te Lin
Keywords:   Chemical Shift Imaging, Ripening, Tomato, Lycopene, Cartenoid

Ripening is an important process for fruits to be more attractive and to create more economic value in the market. For tomatoes, their colors turn from green to red during ripening. This obvious external color change is associated with the accumulation of lycopene. Lycopene is a long-chain unsaturated cartenoid that is beneficial to human health. To gain a better understanding of the synthesis of lycopene during ripening, MRI (Magnetic resonance imaging) technique was employed in this study. CSI (chemical shift imaging) is a branch of MRI technique which provides both spatial and spectroscopic information of the test sample. The spatial structure can be shown as MR images while the chemical properties can be revealed with NMR (nuclear magnetic resonance) spectroscopy. By calculating the intensity of the spectrum of each voxel, the spatial distribution of a specific chemical compound can be displayed in a chemical shift image. This study aims to develop an analytical method to detect the spatial changes of lycopene content in tomatoes during ripening process by using CSI technique. An algorithm was first developed to correct the image artifact due to field inhomogeneity, and thus to visualize the spatial distribution of lycopene internal of the same tomato before and after ripening. CSI experiments were performed to acquire tomato images with the same imaging parameters at the mature green stage and the red ripe stage. After comparing the relative distribution area of lycopene content in different ripening stages, the analysis showed that the distribution area of lycopene content increased significantly when the tomatos during ripening. When comparing different parts of a tomato, the increase of lycopene content was most manifest in the outer pericarp part. To support the findings from the CSI analyses, HPLC (high performance liquid chromatography) experiments were also carried out to compare the lycopene contents of tomatoes at the mature green stage and the red ripe stage. The results of the HPLC experiments were consistent with that of the CSI analyses.

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