EFFECT OF CYSTEINE AND RIBOSE ON THE VOLATILE THERMAL-DEGRADATION PRODUCTS OF A TRIGLYCERIDE AND 3 PHOSPHOLIPIDS

The effect of the Maillard reaction on the volatile products of the degradation of lipids was investigated using an aqueous model system. This paper reports the changes in amounts of selected aliphatic oxidation products formed when beef triglyceride, beef phospholipid, egg phosphatidylcholine and egg phosphatidylethanolamine were heated with cysteine and ribose. The thermal degradation products of these lipids were modified considerably in the presence of cysteine and ribose. The most pronounced alteration was a reduction in the amounts of aldehydes detected, especially unsaturated aldehydes. However, this does not appear to constitute an overall antioxidative effect as ketones, also derived from the oxidation of lipid, showed little change. The 1 -alcohols and 2-alkylfurans were increased when cysteine and ribose were heated with phosphatidylcholine, but not with the other lipids. While the effect on alcohols and furans is not fully understood, the depletion of aldehydes is thought to be caused by reactions with the amino or thiol groups of the amino acid. Reactions with amino groups are also believed responsible for the lower levels of unsaturated aldehydes formed from phospholipids containing the ethanolamine moiety.