Effect of different antioxidants on lycopene degradation in oil-in-water emulsions

There is interest in incorporating lycopene into foods because it is a natural pigment and can also play a role in preventing disease. Therefore, the effect of the addition of various antioxidants in lycopene containing oil-in-water emulsions stabilized with Tween 20 at acidic pH was studied in order to determine protection systems against lycopene oxidation. In this model, EDTA showed pro-oxidant activity while other chelators like citric acid and tripolyphosphate showed no effect. The free radical scavengers, propyl gallate (PG), gallic acid (GA), and alpha-tocopherol all had the ability to decrease lycopene oxidation with alpha-tocopherol being the most effective. The combination of 1 mu M alpha-tocopherol and 10 mu M GA was more effective than the individual antioxidants. Addition of ascorbic acid to the combination of alpha-tocopherol and GA system accelerated lycopene loss. These results suggest that by the proper selection of free radical scavenging antioxidants, lycopene stability in oil-in-water emulsions could be significantly improved. Practical applications: Evidence that dietary lycopene decreases the risk for a number of health conditions has generated new opportunities for addition of lycopene to functional foods. A successful strategy to deliver lycopene into foods is by means of oil-in-water emulsions. However, lycopene may decompose thus causing nutritional loss and color fading. In order to prevent this, the effectiveness of various antioxidants and their combinations in Tween 20 stabilized oil-in-water emulsions was studied. Overall, lycopene oxidation in oil-in-water emulsions could be significantly reduced by the proper selection of free radical scavengers. This fact is of interest to food industry for increasing the shelf-life of lycopene containing functional foods where the lycopene is dispersed in the food in the form of an oil-in-water emulsion.