The determination of aggregation size on the emulsion properties of myofibrillar protein

Myofibrillar protein (MP) majorly determines the quality of emulsified meat product. Since MP is sensitive to external stresses, it would easily denature and form aggregates during processing. However, for now, how MP aggregates size affects its emulsion properties is still lacking clarification. In this study, large/small-sized MP aggregate-models with similar structural properties were successfully established through pH-shifting treatment. Specifically, the NaOH–HCl/gluconolactone induced MP aggregates were treated as large aggregate (LA) and small aggregate (SA) models, respectively, which were subsequently validated through transmission electron microscopy (sectional size: LA 282.47 nm2 and SA 104.79 nm2), gel-permeation chromatography (aggregate peak proportion: LA 73.75% and SA 66.86%) and dynamic light scattering (mean volume weight diameter: LA 45.33 μm and SA 26.20 μm). Then, the structural properties were measured to confirm the equivalent conformation for both models, which exhibited similar protein profiles and molecular flexibility values, and same changing trend in the secondary structure as well as protein unfolding level. Under similar spatial conformation, aggregate size could be the dominant factor to determine interfacial behaviors and emulsifying properties of protein aggregate. Smaller aggregates of SA may be beneficial for the higher interfacial diffusion and rearrangement rate, and greater ability to reduce interfacial tension compared with those of LA. Therefore, SA had better emulsion properties than LA with higher emulsifying activity and stability, and lower Turbiscan stability index. These aggregate models have implications for the development of healthy emulsified meat products, which is conducive to more precise control of product quality and sensory.