Light-induced protein and lipid oxidation in cheese: Dependence on fat content and packaging conditions

Abstract

-Photo-oxidation of cheese products has become an issue due to the fact that packaging of cheeses in transparent materials is very frequently used. The present study aimed to investigate the effect of fat content and availability of oxygen on light-induced oxidation in cheese, as we expected that the fat content would affect the oxidation pathways. Two different model cheeses with 5.4% and 18% fat were packed in air and in vacuum, respectively. The contents of protein (dityrosine and dimethyl disulphide (DMDS)) and lipid (lipid hydroperoxides, pentanal, hexanal and heptanal) oxidation products were significantly reduced in vacuum-packed cheeses compared to cheeses packed in air. Protein oxidation correlated to the concentration of lipids in the cheeses, and interactions between the lipid radicals and proteins seemed to be decisive for the generation of dityrosine, whereas the influence of lipid radicals on the generation of the DMDS seemed more ambiguous. The higher levels of dityrosine and DMDS in the cheese with a high fat content indicated that transfer of radicals from the lipids to the proteins occurred. Even though the generation of DMDS was reduced in vacuum-packed cheese when compared to cheese packed in air, DMDS was formed in vacuum-packed cheese.protein oxidation / fat content / light exposure / radical transfer Résumé -Oxydation des protéines et des lipides dans les fromages induite par la lumière : incidence de la teneur en matière grasse et des conditions d'emballage. La photo-oxydation des fromages est devenue un sujet d'intérêt en raison de l'utilisation accrue de matériaux transparents pour le conditionnement les fromages. La présente étude avait pour but d'évaluer l'effet de la teneur en matière grasse et de la disponibilité en oxygène sur l'oxydation photo-induite dans les fromages, car il était attendu que la teneur en matière grasse devait affecter les réactions d'oxydation. Deux modèles de fromage différents, contenant respectivement 5,4 % et 18 % de matière grasse, ont été conditionnés en présence d'air ou sous vide. Les teneurs en produits d'oxydation des protéines (dityrosine, diméthyl disulfide (DMDS)) et des lipides (hydroperoxydes, pentanal, hexanal, heptanal) étaient significativement réduites dans les fromages conditionnés sous vide, en comparaison avec ceux conditionnés sous air. L'oxydation des protéines était corrélée à la concentration en lipides des fromages, et les interactions entre les radicaux lipidiques et les protéines semblaient être déterminantes pour la génération de dityrosine, alors que l'influence des radicaux lipidiques sur la génération du DMDS semblait moins évidente. Les niveaux plus élevés de dityrosine et de DMDS dans le fromage contenant une teneur élevée en matière grasse montraient qu'un transfert de radicaux avait lieu des lipides vers les protéines. Même si la génération de DMDS était réduite dans le fromage conditionné sous vide en comparaison au fromage conditionné sous air, le DMDS se formait dans le fromage conditionné sous vide.oxydation des...

Light-induced protein and lipid oxidation in low-fat cheeses: whey proteins as antioxidants

“…Lipid hydroperoxides were measured according to Dalsgaard et al (2010). Cheese (1 g) was dispersed in 5 mL of demineralised water and mixed by Ultraturax for 45 s. The lipid hydroperoxides were extracted into 10 mL (1:1) methanol/chloroform mixture.…”

“…The volatile compounds (pentanal, hexanal, heptanal and DMDS) were identified and quantified by gas chromatography coupled with mass spectrometry (GC-MS) head space analysis according to Dalsgaard et al (2010). One millilitre of deionized (18.2 MΩ) filtered water (0.22 μm) plus 1 mL of internal standard (100 ng.mL −1 4-methyl-2-pentanone) were transferred to a 12.5-mL vial containing 2 g of light-treated cheese and sealed with Teflon-coated lids before incubation at 37°C for 30 min.…”

“…The column temperature was programmed to stay at 40°C for 4 min followed by an increase from 40 to 120°C with a rate of 5°C·min −1 , a hold time of 5 min, and a subsequent temperature gradient from 120 to 300°C with a rate of 20°C·min −1 . Mass spectral analysis was performed in selected ion monitoring according to the ions determined by the use of a standard for each compound on a quadrupole MSD 5975 (Agilent Technologies, Germany) with a quadrupole temperature of 150°C and a fragmentation voltage of 70 eV according to Dalsgaard et al (2010). The ion source temperature was 230°C, and the interface was 280°C.…”

“…Dityrosine was measured in 1 g of cheese according to Dalsgaard et al (2010). The cheese was dispersed in 5 mL of demineralised (18.2 MΩ), filtered water (0.22 μm), mixed on a whirlmixer for 45 s. Before the cheeses were frozen to −20°C for later analysis, 1 mL of 1 mol.L −1 NaCl in 0.1 mol.L −1 H 2 SO 4 was added to the samples.…”

“…Riboflavin was measured according to Dalsgaard et al (2010). The cheese (1 g) was dispersed in 5 mL of demineralised (18.2 MΩ), filtered water (0.22 μm) and mixed for 30 s on a Whirl mixer.…”