Influence of emulsifier on lipid oxidation in spray-dried microencapsulated O/W emulsions

Abstract: Lipid oxidation limits the shelf-life of dried microencapsulated oils (DMOs), such as infant formula. The influence of the type of emulsifiers used in such systems is not fully understood yet. Therefore, we investigated the effect of whey protein isolate (WPI), pea protein isolate (PPI), and CITREM on the lipid oxidation of the free and encapsulated fat fractions in DMOs. The DMO with PPI showed hardly any oxidation (8 mmol hydroperoxides/kg oil) during a seven weeks’ incubation at 40 °C, while the formulations with WPI and CITREM showed a comparably high degree of oxidation (133 and 169 mmol/kg, respectively). We hypothesized that the high stability of DMO with PPI was (partly) due to chelation of catalytic metal ions by phytic acid. However, we showed that the oxidative stability of DMOs with either WPI or CITREM was not improved by the addition of phytic acid. Next, we investigated the effect of emulsifier on the lipid oxidation kinetics of the free and encapsulated fat fractions. Only a minor difference was observed between the fat fractions for all formulations, which was attributed to the low selectivity of the fat fractionation by hexane as shown by Raman microscopy. This research shows the potential of using PPI to produce oxidatively stable DMOs and the importance to assess the selectivity of fat fractionation protocols.