Some molecular and functional properties of albumin (83.6% protein), globulin (95.5% protein), glutelin (81.3% protein) as well as protein isolate (80.7% protein) from cashew nut were investigated. These proteins were subjected to molecular (circular dichroism, gel electrophoresis, scanning electron microscopy) and functional (solubility, emulsification, foaming, water/oil holding capacity) tests. Cashew nut proteins represent an abundant nutrient with well-balanced amino acid composition and could meet the requirements recommended by FAO/WHO. SDS-PAGE pattern indicated cashew nut proteins were mainly composed of a polypeptide with molecular weight (MW) of 53 kDa, which presented two bands with MW of 32 and 21 kDa under reducing conditions. The far-UV CD spectra indicated that cashew proteins were rich in β-sheets. The surface hydrophobicity of the protein isolate was higher than that of the protein fractions. In pH 7.0, the solubility of protein fractions was above 70%, which was higher than protein isolate at any pH. Glutelin had the highest water/oil holding capacity and foaming properties. Protein isolate displayed better emulsifying properties than protein fractions. In summary, cashew nut kernel proteins have potential as valuable nutrition sources and could be used effectively in the food industry.

Protein–polyphenol interactions influence emulsifying properties in both directions. Puerarin (PUE) is an isoflavone that can promote the formation of heat-set gels with whey protein isolate (WPI) through hydrogen bonding. We examined whether PUE improves the emulsifying properties of WPI and the stabilities of the emulsions. We found that forming composites with PUE improves the emulsifying properties of WPI in a concentration-dependent manner. The optimal concentration is 0.5%, which is the highest PUE concentration that can be solubilized in water. The PUE not only decreased the droplet size of the emulsions, but also increased the surface charge by forming composites with the WPI. A 21 day storage test also showed that the maximum PUE concentration improved the emulsion stability the most. A PUE concentration of 0.5% improved the stability of the WPI emulsions against environmental stress, especially thermal treatment. Surface protein loads indicated more protein was adsorbed to the oil droplets, resulting in less interfacial WPI concentration due to an increase in specific surface areas. The use of PUE also decreased the interfacial tension of WPI at the oil–water interface. To conclude, PUE improves the emulsifying activity, storage, and environmental stability of WPI emulsions. This result might be related to the decreased interfacial tension of WPI–PUE composites.