Surface adsorption behaviour of milk whey protein and pectin mixtures under conditions of air–water interface saturation

Interfacial Rheological Study of β-Casein/Pectin Mixtures at the Air/Water Interface

Colloidal food products, such as emulsions, foams, gels, and dispersions, are complex systems that need the presence of stabilizing agents to enable their formation and provide stability. Proteins are often used for food foams and emulsions because of their ability to lower interfacial tension and make viscoelastic interfaces. Generally, to improve the resistance against rupture, polysaccharides are used in association with the proteins. Pectin is a complex polysaccharide that can help to stabilize foams or emulsions. This work aims at studying the mechanical resistance of the interface formed by mixtures of β-casein and pectin at high and low methoxylation degrees at the air/water interface using dilatational and shear kinematics. Frequency sweep tests, in the linear region, were performed in shear at different aging times and in dilatational mode, and the rheological data were analyzed. The transient data of the surface tension were analyzed by kinetic models to obtain the characteristic rates of the interfacial phenomena. The kinetic mechanisms of the protein/pectin mixed systems are controlled by protein and show a weak gel behavior for short aging times. The interfaces obtained with both pectins in a mixture with β-casein evolved with time, gelling and showing a solid-like behavior at concentrations of 1 and 10 g/L and after 3.5 h of aging time. The interfacial shear trend obtained suggests a good stabilizing effect of the pectins from citrus with long aging times.

Light-dimerization telechelic alginate-based amphiphiles reinforced Pickering emulsion for 3D printing

Functional Pickering emulsions that depend on the interparticle interactions hold promise for building template materials. A novel coumarin-grafting alginate-based amphiphilic telechelic macromolecules (ATMs) undergoing photo-dimerization enhanced particle-particle interactions and changed the self-assembly behavior in solutions. The influence of self-organization of polymeric particles on the droplet size, microtopography, interfacial adsorption and viscoelasticity of Pickering emulsions were further determined by multi-scale methodology. Results showed that stronger attractive interparticle interactions of ATMs (post-UV) endowed Pickering emulsion with small droplet size (16.8 μm), low interfacial tension (9.31 mN/m), thick interfacial film, high interfacial viscoelasticity and adsorption mass, and well stability. The high yield stress, outstanding extrudability (n₁ < 1), high structure maintainability, and well shape retention ability, makes them ideal inks for direct 3D printing without any additions. The ATMs provides an increased capacity to produce stable Pickering emulsions with tailoring their interfacial performances and, providing a platform for fabricating and developing alginate-based Pickering emulsion-templated materials.

Synergy in Aqueous Systems Containing Bioactive Ingredients of Natural Origin: Saponin/Pectin Mixtures

Biocompatible and biodegradable ingredients of natural origin are widely used in the design of foam and emulsion systems with various technological applications in the food, cosmetics and pharmaceutical industries. The determination of the precise composition of aqueous solution formulations is a key issue for the achievement of environmentally-friendly disperse systems with controllable properties and reasonable stability. The present work is focused on the investigation of synergistic interactions in aqueous systems containing Quillaja saponins and Apple pectins. Profile analysis tensiometer (PAT-1) is applied to study the surface tension and surface dilational rheology of the adsorption layers at the air/solution interface. The properties and the foam films (drainage kinetics, film thickness, disjoining pressure isotherm, critical pressure of rupture) are investigated using the thin-liquid-film (TLF) microinterferometric method of Scheludko–Exerowa and the TLF-pressure-balance technique (TLF-PBT). The results demonstrate that the structure and stability performance of the complex aqueous solutions can be finely tuned by changing the ratio of the bioactive ingredients. The attained experimental data evidence that the most pronounced synergy effect is registered at a specific saponin:pectin ratio. The obtained information is essential for the further development of aqueous solution formulations intended to achieve stable foams based on mixtures of Quillaja saponins and Apple pectins in view of future industrial, pharmaceutical and biomedical applications.

Physicochemical Characterization of an Exopolysaccharide Produced by Lipomyces sp. and Investigation of Rheological and Interfacial Behavior

The present study aimed to evaluate the rheological and interfacial behaviors of a novel microbial exopolysaccharide fermented by L. starkeyi (LSEP). The structure of LSEP was measured by LC-MS, ¹H and ¹³C NMR spectra, and FT-IR. Results showed that the monosaccharide composition of LSEP was D-mannose (8.53%), D-glucose (79.25%), D-galactose (7.15%), and L-arabinose (5.07%); there existed the anomeric proton of α-configuration and the anomeric carbon of α- and β-configuration; there appeared the characteristic absorption peak of the phosphate ester bond. The molecular weight of LSEP was 401.8 kDa. The water holding capacity (WHC, 2.10 g/g) and oil holding capacity (OHC, 12.89 g/g) were also evaluated. The results of rheological properties showed that the aqueous solution of LSEP was a non-Newtonian fluid, exhibiting the shear-thinning characteristics. The adsorption of LSEP can reduce the interfacial tension (11.64 mN/m) well and form an elastic interface layer at the MCT–water interface. Such functional properties make LSEP a good candidate for use as thickener, gelling agent, and emulsifier to form long-term emulsions for food, pharmaceutical, and cosmetic products.

Soy/whey protein isolates: interfacial properties and effects on the stability of oil-in-water emulsions

BACKGROUND

The adsorption of proteins at oil/water interfaces can reduce interfacial tension and increase emulsion stability. However, emulsions stabilized by soy protein isolate (SPI) are not sufficiently stable. Using SPI as a control, a theoretical basis for the adsorption behavior of mixed SPI and whey protein isolate (WPI) at the oil/water interface was established and the effects of the protein ratio and content on the emulsion stability were studied.

RESULTS

Compared to SPI solution, SPI-WPI mixed solutions were found to reduce the size distribution of emulsion droplets and significantly improve the emulsion stability. Among the studied protein contents and ratios, the protein content of 0.2 g kg^-1 and SPI/WPI mass ratio of 1:9 offered the lowest creaming stability index (15%), the smallest droplet size (278 nm), and the largest absolute value ζ-potential (35 mV), i.e. the emulsion stability was excellent. The largest dilatational modulus (10.08 mN m^-1 ), dilatational elasticity (10.01 mN m^-1 ), and dilatational viscosity (1.18 mN m^-1 ), were observed with a protein content of 0.15 g kg^-1 (SPI/WPI ratio of 1:9), along with a high interfacial protein adsorption capacity (47.33%). SPI-WPI complexes form a thick adsorption layer around oil droplets, resulting in an increase of the expansion modulus of the interfacial layer.

CONCLUSION

SPI-WPI complexes can form a thick adsorption layer around oil droplets, resulting in increased expansion modulus of the interfacial layer, which improves emulsion stability. © 2020 Society of Chemical Industry.

Interfacial properties of ultrahigh methoxylated pectin

The interfacial properties of ultrahigh methoxylated pectin (UHMP) prepared via esterification of citrus pectin (CP) were investigated. The intrinsic viscosity ([η]) of pectin was significantly decreased from 1211.5 mL/g to 294.9 mL/g as the degree of methylation (DM) increased from 63.18 ± 0.08% to 91.52 ± 0.11%. Surface tension (γ) analysis indicated that UHMP had a critical micelle concentration (CMC) of 0.8 g/L, which was slightly smaller than that of sugar beet pectin (SBP) (1.0 g/L). The morphology of the UHMP aggregation presented a network structure and irregular clusters at 10 μg/mL and 1 μg/mL based on atomic force microscopy (AFM). Transmission electron microscopy (TEM) observations further confirmed the self-aggregation behaviours and rod-like micelles of UHMP. The surface excess (Γ) was 1.69 ± 0.17 μmol/m² for UHMP, which was lower than the values of SBP (1.88 ± 0.21 μmol/m²) and CP (2.91 ± 0.57 μmol/m²). Correspondingly, UHMP possessed the highest molecular area (A) of 0.99 ± 0.10 nm². Thus, UHMP was proposed to be more flexible and extendable at the interface. The interfacial shear rheology study suggested that UHMP was able to form an elastic-dominant interfacial film to stabilize the oil/water interface.

Study on the Emulsifying Properties of Pomegranate Peel Pectin from Different Cultivation Areas

Pomegranate peel pectin is an important acidic anionic plant polysaccharide which can be used as a natural emulsifier. In order to study its emulsifying properties, this paper systematically analyses pomegranate peel pectin samples from Chinese Xinjiang, Sichuan and Yunnan provinces, through rheometer, interfacial rheometer, Zetasizer Nano-ZS and mastersizer. It is shown that pomegranate peel pectin can effectively reduce the oil-water interfacial tension, reaching an emulsion droplet size of only 0.507 μm, 0.669 μm and 0.569 μm, respectively, while the pectin concentration is 1.5% and the oil phase (MCT) is 10%. It has also shown that the extreme conditions of pH and ion strength can not significantly change its emulsion stability. However, freeze-thaw cycles can cause the pomegranate peel pectin emulsion to become less stable. Furthermore, the effects of decolourization, protein removal and dialysis on the emulsifying properties of pomegranate peel pectin are investigated using mastersizer rheometer and interfacial rheometer. It is found that the protein and pigment in pomegranate peel pectin have little effect on its emulsifying properties, while the results from dialyzed pectin show that the small molecule substances can reduce the emulsion particle size and increase the emulsion stability. The research outcomes of this study provide technical support for the further application of pomegranate peel pectin in the food industry.

Development of a soy protein isolate–carrageenan–quercetagetin non-covalent complex for the stabilization of β-carotene emulsions

The current study investigated the application of a soy protein isolate (SPI), κ-carrageenan (CG) and quercetagetin (Qut) non-covalent complex in stabilizing β-carotene emulsions.

Pectin/Al2O3–ZrO2 core/shell bead sorbent for fluoride removal from aqueous solution

Pectin/Al₂O₃–ZrO₂ core/shell beads were prepared for fluoride removal. A maximum adsorption capacity was 98.077 mg g⁻¹, and the pectin/Al₂O₃–ZrO₂ sorbent could be a potentially material in the fluoride removal by comparing with other sorbent.