Impact of green tea catechins on the oxidative stability of polyunsaturated fatty acid-rich oils

Lipid oxidation is one of the major causes of deterioration in edible oils, negatively affecting the sensory and nutritional properties of foods and limiting product acceptability. To curb the oxidation of oils during storage and when incorporated into food products, we investigated the effect of green tea catechins on the oxidative stability of oils with a high PUFA content, including DHA-rich oil, linseed oil and sacha inchi oil. The effect of catechins was also evaluated in salad dressings, mayonnaise and crackers enriched with these oils. We showed that green tea extracts (GTEs) enhance the oxidative stability of these oils by limiting the formation of hydroperoxides and their breakdown into secondary oxidation products, decreasing the degradation of fatty acids and inhibiting or reducing the losses in tocopherols. The GTEs were also effective antioxidants in complex food systems enriched with ALA, such as salad dressings and mayonnaise. However, a pro-oxidant effect of GTE was observed in crackers enriched with ALA and DHA, most likely due to the cooking process and interaction of catechins with other compounds in the matrix. In addition, we demonstrated that the antioxidant activity of GTE in the DHA-rich oil was influenced by its catechins profile. GTE rich in epigallocatechin showed more potent antioxidant activity in DHA-rich oil than a GTE rich in epigallocatechin gallate. The efficiency of GTE was also shown to be dose-dependent. Thus, the concentration of catechins in the extract and the quantity of extract added to oil or food products is vital to achieving good antioxidant activity. The results of this research indicate that green tea catechins are suitable for use as natural antioxidants in oils with a high PUFA content.