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Journal of Spectroscopy
Volume 2013 (2013), Article ID 789159, 9 pages
http://dx.doi.org/10.1155/2013/789159
Research Article

Fruit-Enhanced Resistance to Microbial Infection Induced by Selective Laser Excitation

Unidad de Láseres y Haces Moleculares, Instituto Pluridisciplinar, Universidad Complutense, 28040 Madrid, Spain

Received 14 June 2012; Revised 28 November 2012; Accepted 3 December 2012

Academic Editor: Luciano Bachmann

Copyright © 2013 Alicia G. Gonzálvez et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Table grapes were irradiated with laser pulses at two different wavelengths: one selected at 302.1 nm, that is, resonant with the transresveratrol biphoton absorption band, and another selected at 300 nm, that is a nonresonant wavelength where trans-resveratrol two-photon absorption is negligible. Attenuated total reflectance Fourier transformed infrared spectroscopic analyses of the irradiated grapes' skin showed an enhancement of polyphenols' content when the resonant wavelength was employed. Furthermore, microbiological analysis performed with nontreated (control), nonresonant, and resonantly irradiated grapes demonstrated how the last samples developed a significantly lower number of colony forming units. Since the only difference between the two (resonant and nonresonant) irradiation conditions was just a couple of nanometres in the employed UV-B laser wavelengths, the germicidal effect should be considered very similar. As a result, the observed difference in the table grape resistance to microbial infection was attributed to a wavelength-dependent-induced photochemistry. Finally, the potentiality of this method to enhance the postharvest health status of table grapes is remarked.