Insight into the oil polarity impact on interfacial properties of myofibrillar protein

The interfacial behaviour of myofibrillar protein is critical to the stability of myofibrillar protein-stabilized oil in water emulsions. However, the effect of oil phase on the interfacial behaviour of myofibrillar protein and the resultant emulsion properties has not been widely analyzed. Therefore, this study was focused on exploring the relationship among oil polarity, the interfacial behaviour of myofibrillar protein and the emulsion physical stability. The results suggested that the surface load, interfacial pressure, diffusion rate, rearrangement rate and dilatational elastic modulus increased with the oil polarity decreasing. This was attributed to the larger extent of myofibrillar protein unfolding on the apolar interfaces which promoted the exposure of hydrophobic groups, leading to an increased protein-oil and protein-protein intermolecular interactions on the interface. However, the oil polarity barely affects the secondary structure of interfacial myofibrillar protein. Intriguingly, the emulsion physical stability was improved with the oil polarity increasing in a certain range despite the impaired viscoelasticity of interfacial film, possibly due to the lower interfacial tension of polar oils. A further increase in polarity exceeding the certain range contrarily reduced the emulsion stability, potentially due to the desorption and collapse of interfacial film. Our results demonstrated that oil polarity and mechanical strength of interfacial film should both be taken into consideration when studying emulsion stability. This knowledge could provide an in-depth understanding to reveal the underlying mechanism of how oil polarity affecting the interfacial behaviour of proteins and consequently the physical stability of the corresponding emulsions.