Oxidation of omega-3 fatty acids under acididc conditions: Activity of phenolic compounds

abstract

English

Incorporation of marine lipids, a source of healthy long-chain omega-3 polyunsaturated acids (DHA and EPA), into processed food consumed on a daily basis, such as bakery and diary products or infant formulas, will increase the level of these acids in the human diet. However, at the same time these products will become more susceptible to oxidative deterioration. One way to sustain oxidative stability of foods enriched with marine lipids is to add antioxidants to the food. During processing and storage, most fatty foods would be in the form of a multiphase system, which is characterized by water and oil phase and the emulsifier interphase, all containing various endogenous elements, including pro-oxidative metals and other potentially pro-oxidative compounds. Location of antioxidants in these systems has been well established as an important parameter for antioxidant activity, however the role of other environmental factors, especially pH, remain unclear. Better knowledge on the influence of pH will benefit food producers to facilitate safe manufacturing and storage conditions, and may improve oxidative stability of low pH products. Moreover, oxidation processes may develop also in the human stomach after consumption of fatty food. This is believed to contribute to development of serious vascular diseases. What role play human gastric juice in post-prandial oxidation is however not yet fully understood. The antioxidant activity of phenolic compounds (caffeic acid, ferulic acid, tocopherol, catechine, propyl gallate, BHT, TBHQ, BHA) was investigated in a food-related system - liposomes made from marine phospholipids. The oxidation kinetics of omega-3 fatty acids was studied both for free iron and hemoglobin catalyzed oxidation. The oxidation experiments were carried out under different pH of the liposome solution, and in the presence of human gastric juice (pH 3.0). Oxygen uptake method was used to quantify the rate of lipid oxidation. This study reports that certain dietary antioxidants may in free iron catalyzed oxidation change their activity in dependency on pH, going from antioxidative (3.5 < pH < 6) to strongly pro-oxidative (pH < 3.5). Both iron and haemoglobin catalyzed oxidation of marine lipids was significantly reduced in acidic environment of gastric juice, as well as was reduced the pro-oxidative activity of pro-oxidative phenolic compounds.

Marine phospholipids, lipid oxidation, oxygen uptake, gastric juice, pH, phenolic antioxidants

KRISTINOVÁ, V.

14. 9. 2009

Copenhagen, Denmark

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