The Effect of Refrigeration on Some Antioxidants and Soluble Proteins in Eggs

In this study we aimed to investigate the effect of refrigeration of eggs from laying hens reared extensively. For this purpose, there were investigated the quantity of eggs polyphenols, their antioxidant activity, protein carbonyl concentration and electrophoretic protein pattern in eggs. Analyzed eggs, both fresh and chilled for 30 days at temperatures below 12°C, were obtained from hens fed with the same type of forage. The study was conducted in January and February, and the parameters analyzed were egg phenols, lycopene and β-carotenoids, total antioxidant capacity, protein electrophoresis in denaturant system and protein carbonyl content. Egg polyphenols concentration was expressed as mg gallic acid equivalents / 100 g egg. The quantitative determination of antioxidant capacity was based on the reduction of Mo(VI) to Mo(V) by the sample analyte and the subsequent formation of a green phosphate/Mo(V) complex at acid pH, while the antioxidant activity was expressed relative to that of ascorbic acid. Total carbonyl content in egg proteins increased with the increase of refrigeration time. Carbonyl content can be considered a marker for protein oxidation. Amino acid residues affected by these changes in proteins may influence the functional properties of eggs. The amounts of β-carotene and lycopene found in refrigerated and fresh eggs were very low; the high contents of phenolic compounds explained the good antioxidant activity determined in all assays. In the present research, we found that the refrigeration for a period of thirty days had no significant effects on polyphenols concentration and also electrophoretic pattern was not influenced by the refrigeration.