Raman spectroscopic study of the epicuticular wax layer of mature mango (Mangifera indica) fruit

Little is known about the chemical composition of the natural wax layer covering mango (Mangifera indica) fruit. We report here on the role of Raman spectroscopy in a study that was undertaken to characterize the epicuticular wax of mature mango fruit. Scanning electron microscope measurements showed two morphologically distinct parts in the wax layer and Raman microscopy determined that they are chemically distinct. Crystalline aliphatic compounds protrude from an amorphous layer in which long-chain aliphatic, aromatic and unsaturated compounds are present. Raman spectra recorded on the perimeter of lenticels indicate an absence of the crystalline aliphatic compounds in this region and this information could assist in the solution of the problem faced by the mango industry of the discoloration around lenticels, which makes the fruit unacceptable as an export product. The results are supported by Fourier transform IR spectroscopy and both techniques are now employed as probes in a long-term project to study dynamic changes of the wax during fruit development and eventual processing, which includes the monitoring of possible changes in carotenoid content and the role of dust particles embedded in the wax. Copyright (C) 2004 John Wiley Sons, Ltd.