Micro‐Raman and fluorescence spectroscopy for the assessment of the effects of the exposure to light on films of egg white and egg yolk

Abstract

In this work, non-destructive techniques were employed for the spectrofluorimetric and micro-Raman differentiation of solid films of egg yolk and egg white as a function of exposure to light. Using both techniques it is possible to discriminate between the samples on the basis of composition and follow some chemical changes involved during the light-ageing of egg proteins and fatty acid esters. In egg white, fluorescence emission spectra highlighted the presence of multiple fluorophores, with an effective broadening of the fluorescence emissions following light exposure, ascribed to the partial oxidation and depletion of tryptophan; in the Raman spectrum of dark-aged egg white a peak at 758 cm −1 is ascribed to the vibrational mode of tryptophan, which is completely absent in the spectrum of samples exposed to light. Changes in the fluorescence of egg yolk following exposure to light are ascribed to the degradation of amino acids, cross-linking between amino acids and the formation of oxygenated triacylglycerides. These results are corroborated with Raman spectra of the light-exposed samples, which are associated with wavenumber shifts with respect to the dark-aged sample for the Amide I and for the characteristic carbonyl vibration at 1744 cm −1 ascribed to the oxidation of fatty acid esters.

A chemometric study of ageing in lead-based paints

“…It is noteworthy that the equivalent fresh samples analysed in our previous study [29] generally did not display such prominent fluorescence backgrounds, and thus this appears to arise to some extent as a result of ageing. The differences in features observed here between naturally-and artificially-aged paints are quite similar to the observations of Osticioli et al [42] from fluorescence-spectroscopy studies, although these were performed with a 230 nm excitation-laser wavelength, and the fluorescence was observed at 380 nm (26,316 cm -1 , a response attributed to the amino acid tryptophan), i.e. far from the spectral region being analysed in the present work.…”

Identification of materials used in a wooden coffin lid covered with composite layers dating back to the Ptolemaic period in Egypt

“…The bands at 1601, 1582, 1448, 1320, 874 and 755 cm -1 in the Raman spectra are assigned to the binding medium, attributable to egg yolk [39][40][41]. These results are supported by the availability of eggs from wild birds, such as geese or ducks in ancient Egypt, while domestic chickens were not introduced until classical times.…”

Recent advances in linear and non‐linear Raman spectroscopy. Part III

“…The results of this study give some insights into the molecular mechanisms by which catechin will prove beneficial for cell protection from free radical-and metal-induced deleterious effects. Osticioli et al [93] reported on a micro-Raman and fluorescence spectroscopic study for the assessment of the effects of light exposure on films of egg white and egg yolk. The purpose of a report by Kinoshita et al [94] was to elucidate the mechanism of sialolith formation, a cause of salivary gland infections, by using Raman micro-spectroscopy to analyse the precise distribution of phosphate and amide III in sialoliths.…”