High internal phase Pickering emulsions stabilized by tea residue protein: Application in β-carotene encapsulation

The increasing production and consumption of tea drinks has led to the generation of large amounts of discarded extracted tea residues. As a result, researchers have attempted to extract tea water-insoluble protein (TP) from discarded tea residues to produce food emulsifiers. Thus, in this study, high-internal-phase Pickering emulsions (HIPPEs) stabilized by TP were developed and characterized. First, the effects of salt ions on the emulsifying properties of TP were examined using interfacial tension and hydrophobicity. Fourier transform infrared spectroscopy was used to determine the suitable range of salt ions in the processing stage. Then, the particle size distribution, microstructure, rheological properties, and stability of the emulsions were systematically investigated by controlling the oil phase volume, particle concentration of TP, and emulsification method. The results showed that TP was effectively adsorbed on the oil-water interface and formed a stable particle layer, which means that TP-stable high-internal-phase Pickering emulsions (TPHIPPEs) has been successfully prepared. Further analysis showed that TPHIPPEs exhibited good stability and gelation properties. The pH range was 7-9, and the salt ion concentration was <0.5 M. Additionally, TPHIPPEs exhibited excellent temperature tolerance and antioxidant ability. Finally, the application development results revealed that the loading and retention rates of β-carotene in TPHIPPEs were significantly higher than those of the control group of camellia oil, and that TPHIPPEs exhibited good resistance to UV light and thermal degradation. This study provides new insights into the high-value utilization of tea residue resources.