Investigation of lipid oxidation and non-enzymatic browning reactions in marine PL emulsions

Marine phospholipids (PL) have received much attention recently due to their numerous advantages. One of these advantages is their better resistance towards oxidation as compared to fish oil. In addition to the antioxidative properties of α-tocopherol and phospholipids, the better oxidative stability of marine PL might be attributed to antioxidative properties of pyrroles formed between oxidised lipids with amine groups from phosphatidylethanolamine (PE) or residues amino acids that are present in marine PL. The main objective of this study was to investigate if the presence of amine group from PE or amino acids affected the oxidative stability of purified marine PL emulsions. The secondary objective was to study the non-enzymatic browning reactions in the emulsions which included both Strecker degradation (SD) and pyrroles formation. Emulsions were prepared with and without addition of amino acids (leucine, methionine and lysine) from 2 authentic standards (PC and PE) and 2 purified marine PL (LC and MPL) through sonication method. Emulsions were incubated at 60 ºC for 0, 2, 4 and 6 days. Non-enzymatic browning reactions were investigated through measurement of i) Strecker aldehydes, ii) yellowness index (YI), iii) hydrophobic and hydrophilic pyrroles content. On the other hand, the oxidative stability of emulsion was measured through secondary lipid derived volatiles. The result showed that the presence of PE and amino acids caused the formation of pyrroles, generated the Strecker aldehydes, decreased the YI development and lowered the lipid oxidation. The lower lipid oxidation in emulsions containing amino acids might be attributed to antioxidative properties of pyrroles or amino acids.