The influence of digestion on the malondialdehyde behaviour in oil-in-water emulsions

In this study the effect of digestion on the stability of malondialdehyde (MDA)-protein adducts was investigated. In vitro digestion model was used. Moreover, the influence of food proteins, emulsifier type, pre-incubation temperature (4 °C or 40 °C) were evaluated. MDA recoveries in aqueous buffer, protein solutions, pure saturated oil and O/W emulsions which stabilized by polyoxyethylene sorbitan monolaurate (Tween 20) or whey proteins were compared. In the presence of proteins, lower MDA recoveries were measured. Moreover protein type affected the concentrations of free MDA content. Oil phase was found more conducive to form of aldol condensation and/or cleavage products. pH was another parameter that affects condensation and/or cleavage reactions. These reactions took place more readily in intestinal environment. MDA molecules showed more reactivity at 40 °C than at 4 °C, so less MDA levels were measured in 40 °C samples. Emulsifier type also affect the revovery. When whey protein was used as an emulsifier more stable adducts were obtain than Tween 20 emulsions. After digestion procedure significant amount of free MDA, its aldol condensation and/or cleavage products and MDA-protein adducts were found and they ready to be assimilated into the body.