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The interaction between whey protein isolate (WPI) and saponins plays a key role in regulating and improving foam properties. In this study, the influences of Xanthoceras sorbifolium Bunge leaves saponins (XLS) on the foaming properties of WPI were characterized. Results revealed that 0.2 or 0.3% XLS could significantly increase the particle size and turbidity, as well as significantly decrease the protein solubility. The spectrum results showed that there was an interaction between WPI and XLS, which caused the change in protein structure and exposed more hydrophobic groups. Importantly, WPI with 0.3% XLS significantly increased the surface hydrophobicity and decreased the surface tension, resulting in better foaming ability and foam stability. Moreover, the rheological determination suggested that WPI with XLS increased both the apparent viscosity and viscoelasticity. The best foaming performance of WPI was achieved with 0.3% XLS at pH 3, along with the formation of the most compact, smallest, and densest bubbles. According to the classification of mixed conditions suggested by principal component analysis and hierarchical clustering analysis, WPI had good scores in the presence of both 0.2% and 0.3% XLS at pH 3, suggesting that XLS is a promising acidic foam additive applied to WPI food foam. • Both pH and XLS can change the interface properties of WPI. • XLS improved both foaming ability and stability of WPI. • XLS improved rheological properties of WPI by change the state of water. • Quantative associations between foam and physicochemical properties were studied. • WPI-XLS dispersions can be used for the development of acidic food foam in dairy industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Non-thermal plasma induced the structural unfolding of WPI (whey protein isolate). • Non-thermal plasma enhanced the binding affinity of WPI to GR 1 (Ginsenoside Rg 1). • Non-thermal plasma improved the antioxidant activity of WPI-GR 1 complexes. • The complexes were used to stabilize soybean oil-in-water emulsions. • Non-thermal plasma treated WPI-GR 1 complexes formed emulsions with smaller droplets. Molecular interaction forces regulate the interfacial properties of oil-in-water emulsion and play a key role in the rheology and stability of the emulsion in the food industry. In this study, the effects of non-thermal plasma (NTP) treatment on the structural and functional properties of whey protein isolate (WPI) and its binding interaction with ginsenoside Rg 1 (GR 1) were investigated. The results based on surface hydrophobicity, infrared spectroscopy and fluorescence spectroscopy test showed that the NTP treatment induced the unfolding of the structure of WPI and promoted the binding affinity between WPI and GR 1. By comparing with untreated WPI (an α-helix content of 19.63 % and a β-sheet content of 31.66 %), there was a greater decrease in α-helix content and an increase in β-sheet content of WPI in N 20 -WPI (α-helix = 9.63 %, β-sheet = 39.63 %) and N 20 -WPI-GR 1 (α-helix = 4.98 %, β-sheet = 48.66 %) groups. Importantly, the NTP treatment increased the interfacial adsorption and antioxidant capacity of the WPI-GR1 complexes, which contributed to the improvement of the rheological properties and oxidation stability of the emulsion. As a result, the NTP treatment could markedly improve the rheological and antioxidative properties of the WPI-GR 1 complexes and the NTP-treated WPI-GR 1 emulsions was more stable than that untreated. The present research indicated that NTP-treated formation of protein-saponin complexes could enhance the functional properties of the proteins, thus expanding their application as functional ingradients in nutritionally fortified food. [ABSTRACT FROM AUTHOR]