Structure and rheological properties of oil-water and air-water interfaces stabilized with micellar casein isolate and whey protein isolate mixtures

Multiscale approach to the characterization of the interfacial properties of micellar casein and whey protein blends and their effects on recombined dairy creams

In this study, whipped cream with blends of micellar casein (MCN) and whey protein (WPI) in different ratios were prepared to investigate the role of protein interfacial behavior in determining foam properties at multiple scales, using theoretical modeling, and microscopic and macroscopic analysis. Fluid force microscopy has been used for the first time as a more realistic and direct means of analyzing interfaces properties in multiphase systems. The adsorption kinetics showed that the interfacial permeability constant of WPI (4.24 × 10-4 s-1) was significantly higher than that of the MCN (2.97 × 10-4 s-1), and the WPI interfacial layer had a higher modulus of elasticity (71.38 mN/m) than that of the MCN (47.89 mN/m). This model was validated via the mechanical analysis of the fat globules in real emulsions. The WPI-stabilized fat globule was found to have a higher Young's modulus (219.67 Pa), which contributes to the integrity of its fat globule morphology. As the ratio of MCN was increased in the sample, however, both the interfacial modulus and Young's modulus decreased. Moreover, the rate of partial coalescence was found to increase, a phenomenon that decreased the stability of the emulsion and increased the rate of aeration. The mechanical analysis also revealed a higher level of adhesion between MCN-stabilized fat globule (25.16 nN), which increased fat globule aggregation and emulsion viscosity, while improving thixotropic recovery. The synergistic effect of the blended MCN and WPI provided the highest overrun, at 194.53 %. These studies elucidate the role of the interfacial behavior of proteins in determining the quality of whipped cream and provide ideas for the application of proteins in multiphase systems.

Interfacial Behavior and Long-Term Stability of the Emulsions Stabilized by Sugar Beet Pectin-Ca2+ Complexes with Different Cross-Linking Degrees

Recent studies showed that sugar beet pectin exhibited more excellent emulsifying properties than traditional citrus peel pectin and apple pectin ascribed to the higher content of neutral sugar, protein, ferulic acid, and acetyl groups. It is precisely because of the extremely complex molecular structure of pectin that the emulsifying properties of the pectin-Ca2+ complex are still unclear. In this study, SBP-Ca2+ complexes with different cross-linking degrees were prepared. Subsequently, their interfacial adsorption kinetics, the resistance of interfacial films to external perturbances, and the long-term stability of the emulsions formed by these SBP-Ca2+ complexes were measured. The results indicated that the highly cross-linked SBP-Ca2+ complex exhibited slower interfacial adsorption kinetics than SBP alone. Moreover, compared with SBP alone, the oil-water interfacial film loaded by the highly cross-linked SBP-Ca2+ complex exhibited a lower elasticity and a poorer resistance to external perturbances. This resulted in a larger droplet size, a lower ζ-potential value, a larger continuous viscosity, and a worse long-term stability of the emulsion formed by the highly cross-linked SBP-Ca2+ complex. This study has very important guiding significance for deeply understanding the emulsification mechanism of the pectin-Ca2+ complex.

Effect of Corn Starch Granules on Stabilizing the Foam Structure of Ultrasonically Modified Whey Isolate Protein

In this study, the mechanism of ultrasound combined with corn starch granules (CSG) treatment improved the foam properties of whey protein isolates (WPI) and was systematically investigated. The results showed that ultrasound combined with corn starch granules treatment increased foam capacity and stability by 15.38% and 41.40%, respectively. Compared with the control group, corn starch granules enhanced the surface charge (52.38%) and system turbidity (51.43%), which certainly provided the necessary conditions for the improvement of foam stabilization stability. In addition, corn starch granules as microgel particles increased the mechanical properties of the interfacial protein film, thus delaying the instability of foam. This research would provide new insights into the design of new protein-based foam foods in the future food industry.