Label-Free Mapping of the Biochemicals in Tomato Fruit by Confocal Raman Microspectroscopy
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Raman scattering-based technique coupled with microscope provides information about the chemical structure of biological specimen at the molecular and cellular scale nondestructively without the requirement of chemical extraction. Confocal Raman microspectroscopy presents a new approach for investigating the cellular structure of vegetables and fruits and the biochemical contents in them. This study describes potential of the confocal Raman microspectroscopy for the evaluation of biomolecules and their distribution in the various parts of ripened tomato fruit. For this, Raman spectra of the exocarp, mesocarp and endocarp of the red tomato fruit have been acquired in the spectral region < 2000 cm−1 at a resolution of 4 cm−1 using confocal Raman spectrometer equipped with 785 nm excitation laser. The recorded spectra depict spectral signatures of cuticular wax which is detected only in the exocarp, while signatures of lycopene, carotene, phenolic compounds and carbohydrates (starch, glucose and fructose) show their presence in all the parts of tomato fruit with varying concentration. Amino acid and pectin are detected only in the region of mesocarp and endocarp. Principal component analysis has been applied to discriminate among the detected biomolecules in different parts of the tomato fruits.
KeywordsConfocal Raman microspectroscopy Biochemical analyses Principal component analysis Vegetables Tomato
Authors are thankful to UGC, New Delhi, for providing financial assistance to create confocal Raman facility under UGC–CAS program to the Department of Physics, University of Allahabad, Allahabad. Sweta Sharma and Abhi Sarika Bharti are also thankful to UGC, New Delhi, for the financial assistance in the form of SRF fellowship.
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