Improving the Stability of Protein-based High Internal Phase Emulsions by Two-step Emulsifying Method
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Abstract:
In this study, taking native bovine serum albumin (BSA) as the protein model, two-step emulsification was used to improve the stability of protein-based high internal phase emulsions (HIPEs) without causing protein denaturation. Firstly, an initial emulsion (micro-droplets) with φ as 0.2 and d4,3 (volume-averaged diameter) in the range of 17.60~0.42 μm, was prepared by high-energy homogenization (high speed homogenization 30000 r/min, ultrasonication and microfluidization). Then, HIPEs (φ=0.8) were fabricated using micro-droplets as the Pickering stabilizer through low-energy homogenization (high speed homogenization at 13500 r/min). HIPEs with different properties were prepared by changing the protein concentrations and the homogenization energy for the preparation of initial emulsions. The interfacial protein adsorption rate (AP%), particle size of the initial emulsions were characterized, while their appearance, microstructure and rheological characteristics were examined before and after a 20 day storage at room temperature. Finally, a comparative experiment to remove free proteins and a thermal stability test of HIPEs were conducted. It was found that the most suitable protein concentration was 1 wt%, even at a concentration as low as 0.1 wt%, HIPEs remained stable and still after being turned upside down. The stability of HIPEs was effectively improved when the d4,3 of micro-droplets was not higher than 2.16 μm. The results showed that the presence of micro-droplets significantly improved the storage stability and thermal stability of HIPEs.
