Direct technique for monitoring lipid oxidation in water-in-oil emulsions based on micro-calorimetry

- Microcalorimetry allows monitoring lipid oxidation, in real time, directly in water-in-oil emulsions.
- Enthalpy values are correlated with primary oxidation products (conjugated dienes) of the emulsified oils.
- The oxidability of water-in-oil emulsions can be directly compared using the microcalorimetry characterization.
- The oxidability parameter is correlated with α-linolenic acid content of the plant oils used for the emulsion formulation.

An experimental device based on the measurement of the heat flux dissipated during chemical reactions, previously validated for monitoring lipid oxidation in plant oils, was extended to follow lipid oxidation in water-in-oil emulsions. Firstly, validation of the approach was performed by correlating conjugated diene concentrations measured by spectrophotometry and the heat flux dissipated by oxidation reactions and measured directly in water-in-oil emulsions, in isothermal conditions at 60 °C. Secondly, several emulsions based on plant oils differing in their n-3 fatty acid content were compared. The oxidability parameter derived from the enthalpy curves reflected the α-linolenic acid proportion in the oils. On the whole, the micro-calorimetry technique provides a sensitive method to assess lipid oxidation in water-in-oil emulsions without requiring any phase extraction.