# Combined Effect of Plant Protein Isolate Content and the Homogenization Processes on the Physical Stability of Oily Extract Emulsions

## TL;DR

This study shows that using soy protein isolate with microfluidization creates more stable oil emulsions than other methods.

## Contribution

The novel contribution is demonstrating how microfluidization and soy protein isolate enhance emulsion stability and rheological properties.

## Key findings

- Emulsions with soy protein isolate and microfluidization had a TSI of 0.85 and droplet size of 160.1 nm.
- Microfluidization emulsions showed pseudoplastic flow behavior transitioning to Newtonian at higher shear rates.
- Rotor–stator systems had lower stability with TSI of 5.7 and droplet sizes over 1700 nm.

## Abstract

The homogenization methods and selection of biomaterials of the continuous phase are critical in the formulation of food emulsions. This study evaluated the stability of emulsions containing an oily extract using soy protein isolate (SPI), pea protein isolate (PPI), and two homogenization techniques: microfluidization (MF) and rotor–stator (RS). Emulsions formulated with SPI and processed by MF exhibited the highest stability, with a Turbiscan Stability Index (TSI) of 0.85, a mean droplet size of 160.1 nm, a polydispersity index of 0.152, a ζ-potential of −29.3 mV, and an apparent viscosity of 8.1 mPa·s. The PPI emulsions processed by MF showed slightly higher TSI (1.6) and droplet size (188.1 nm). All MF emulsions achieved desirability >0.8. The RS systems showed lower stability, with a TSI of 5.7 (SPI) and 7.9 (PPI), and droplet sizes >1700 nm, despite more negative ζ-potentials (−40.2 mV for SPI, −36.7 mV for PPI). All optimized emulsions showed pseudoplastic flow behavior, with a transition to Newtonian flow at higher shear rates. Overall, microfluidization significantly improved emulsion stability and rheological properties.