Effect of ingredients on oxidative stability of fish oil-enriched drinking yoghurt

The oxidative stabilities of fish oil-enriched milk and fish oil-enriched drinking yoghurt were compared by following the development of lipid oxidation in plain milk, plain yoghurt and yoghurt to which ingredients present in drinking yoghurt were added one by one. All samples were enriched with 1 wt-% fish oil. After 3 weeks of storage, development of peroxide values, volatile secondary oxidation products and fishy offflavors were much more pronounced in the milk compared to any of the yoghurt samples, irrespective of any added ingredients used to prepare flavored drinking yoghurt. Thus, pectin, citric acid or gluconodelta- lactone did not affect the oxidative stability of fish oil-enriched yoghurt emulsions. Furthermore, the fruit preparation and added sugar did not lead to increased antioxidative activity. It is concluded that yoghurt as the dairy component in the fish oil-enriched emulsion was responsible for the remarkably high oxidative stability and was able to protect the n-3 PUFA against oxidative deterioration. It should be considered that this strong antioxidative effect of yoghurt might mask potential antioxidative effects of the other ingredients in the drinking yoghurt.