Effect of Extraction Procedures on Fluorescent Chromophores in Milk

The oxidation of membrane lipids of freeze-dried Milk Fat Globule Membranes (MFGM) was studied using a fluorescence technique involving two different extraction procedures to obtain lipophilic fluorescent chromophores. MFGM underwent extensive lipid oxidation when stored under air, at controlled temperature and humidity and fluorescent compounds were formed with excitation maxima at 350 nm and emission maxima at 440 nm. Direct extraction of fluorescent compounds with an organic solvent mixture (Cl₃CH:CH₃OH 2:1 v/v) gave reproducible results reflecting well the progress of oxidation. Solvent extraction after previous reconstitution (to original water content) of the dry samples was less satisfactory.