Monitoring the identity and the structure of soft cheeses by fluorescence spectroscopy

Abstract

Soft cheeses exhibit a wide range of textures and, as a consequence, of structures. The objective of the present study was to investigate intrinsic fluorophores of cheese in order to discriminate between eight different soft cheeses. Protein tryptophan emission spectra and vitamin A excitation spectra were recorded directly on cheese samples using front face fluorescence spectroscopy. The eight soft cheeses were discriminated using their spectra by applying multivariate statistical methods such as principal component analysis and factorial discriminant analysis. From the tryptophan fluorescence data set, a good classification was observed for 95% and 92% of the principal and test samples, respectively. A better classification (96% and 93% for principal and test samples) was obtained from the vitamin A spectra. The spectral pattern associated with the principal components provides characteristic wavelengths which are the most suitable for separating the spectra. They allow information on the protein structure at the molecular level to be derived, in relation with cheese texture. cheese / identification / structure / fluorescence / protein Résumé-La spectroscopie de fluorescence frontale pour identifier et caractériser la structure de fromages à pâte molle. Les fromages à pâte molle présentent une large gamme de texture et, en conséquence, de structure. L'objectif de cette étude était d'évaluer le potentiel des fluorophores intrinsèques du fromage dans la discrimination de 8 types de fromages à pâte molle. Les spectres d'émission des tryptophanes de protéines et les spectres d'excitation de la vitamine A ont été enregistrés directement sur des fromages au moyen de la fluorescence frontale. L'analyse des collections de spectres par des méthodes statistiques multidimensionnelles telles l'analyse en composantes

Article

“…The maximum in the emission spectra of TRP was found at a relatively higher value than in previous papers, 340-342 nm against 330-333 nm, either in emulsions with dairy proteins, in processed milk or in soft cheeses [9,10,17,18]. This shift of the maximum cannot be due to the heat treatment of milk.…”

“…Front-face fluorescence spectroscopy is a powerful technique for dynamic studies of colloidal non-transparent systems such as dairy emulsions [9], acid or rennet gels [9,[14][15][16][17] or even cheeses [11,18]. The fluorescence spectrum of a probe in the food product is related to its environment.…”

Potentiality of front-face fluorescence spectroscopy to determine the geographic origin of milks from the Haute-Loire department (France)

“…PCA was applied to the normalised spectra in order to investigate differences in the spectra [18,20]. This statistical multivariate treatment made it possible to draw similarity maps of the samples [1,22].…”

“…Fluorescence spectroscopy is a sensitive and rapid analytical technique that provides information on the presence Geographic origin of milks 225 of fluorescent molecules such as tyrosine, phenylalanine and tryptophan residues in proteins, and their environment in biological samples. The fluorescence properties of aromatic amino acids have also been used to study protein structure and protein interactions in dairy products [20]. The potential of using fluorescence in food research has increased during the last few years with the propagated application of chemometrics and with technical and optical developments of spectrofluorimeters.…”

“…The potential of using fluorescence in food research has increased during the last few years with the propagated application of chemometrics and with technical and optical developments of spectrofluorimeters. It has been shown that front-face fluorescence spectroscopy can discriminate milk samples subjected to heat treatment from those subjected to homogenisation [13] and monitor structural changes occurring during milk coagulation [14,18,19] and cheese manufacture [20,32,33]. In addition, this technique has been used for the determination of lactulose and furosine in milks [28] and the evaluation of oxidative changes in processed cheese during storage [9,34,41].…”