Fluorescence in aldehyde model systems related to lipid oxidation

To better understand the formation of fluorescent compounds in foods undergoing lipid oxidation, five different model systems were studied by fluorescence spectroscopy. In each system the formation of fluorescence resulting from reactions between protein and carbonyl compounds at 4 °C in biological systems was investigated. In model systems 1 and 2, the amino acids glycin and lysine were added aldehydes with different extent of saturation and chain length. In model systems 3–5, aldehydes were added to minced turkey, pork, and cod meat. When excited at 382 nm, different combinations of aldehydes and amino acids resulted in broad and slightly differently shaped fluorescence spectra and the overall intensity increased logarithmically for 14 days. The same trend was found for the meat systems. For the meat systems, the fluorescence intensity increased in accordance with degree of aldehyde saturation, and aldehydes with double bonds in 2,4 position gave generally higher intensity than the aldehyde with double bond in 2,6 position. Differences in spectral shape originating from different aldehydes suggest that fluorescence might be able to detect and quantify oxidation related to different groups of aldehydes. This paper illustrates that results from simple model systems are not always comparable to results from biological materials.