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In recent years, the demand for foods without animal proteins has increased, both for health and ethical reasons. Replacing animal protein in foods can result in unappealing textures, hindering consumer acceptance. In this context, interfacial properties also play a crucial role in food systems like foam or emulsions. Therefore, the interfacial rheological behavior at the air–water interface of pea protein isolate (PPI) has been investigated to understand how affects food foam production. The PPI has been studied without modification and also through enzymatic treatment with transglutaminase (TG) to understand the interfacial properties of the modified proteins. Data obtained by static measurements have shown a surface activity of PPI comparable with other vegetable proteins, while the treatment with TG does not significantly alter the surface tension value and the interfacial adsorption rate. Differences have been found in the rearrangement rate, which decreases with TG, suggesting a possible crosslinking of the pea proteins. The PPI modified with TG, studied in dynamic conditions both in dilation and shear kinematics, are less elastic than PPI that is untreated but with a higher consistency, which may lead to poor foam stability. The lower complex interfacial modulus obtained under shear conditions also suggests a low long-time stability. [ABSTRACT FROM AUTHOR]

The interfacial activity of commercial low-methoxy (LM) and high-methoxy (HM) pectins from citrus peel was investigated at air-water interfaces by focusing on the role of their molecular weight (MW) and degree of methoxylation (DM). A pendant drop tensiometer was used to carry out transient interfacial tension measurements and small amplitude oscillations. Different pectin concentrations (ranging between 0.00001 g/100 g and 5 g/100 g) and pH conditions (4 and 6) were used during the tests. It was observed that citrus pectins are characterised by interesting surface properties that could allow potential practical uses. Experimental results evidenced that MW affects the diffusion of molecules towards the interface, whereas other investigated parameters (i.e. surface tension, adsorption rate, dynamic moduli) seem more dependent on DM and a clear dependence on MW was not observed. pH conditions modify intermolecular interactions in the bulk and surface layer, even if their effects are related to the fraction and distribution of carboxylic groups along the chain. As a consequence, a complex dependence on investigated parameters was observed and no clear relationship was obtained. Nevertheless, among tested commercial samples LM pectins exhibited the most interesting properties and this behaviour seems related to the intermolecular interactions occurring among them. [ABSTRACT FROM AUTHOR]

Proteins are widely used in the formation and stabilization of multiphase systems, thanks to their ability to adsorb at the interface reducing the interfacial tension and promoting the formation of viscoelastic layers. Owing to the growing consumer demand, the food industry is moving toward the growing use of plant-based proteins, suitable for consumers who do not eat products of animal origin, for either ethical or health reasons. Nevertheless, the scientific literature lacks information on the surface activity and emulsifying ability of these proteins. In this work, the interfacial properties of soy, hemp and brown rice isolate proteins were investigated at the interface with commercial sunflower oil (O/W) to evaluate their characteristics in view of potential uses in food applications such as emulsions, sauces, dressing, topping and soft foods. Dilatational and shear kinematic, with pendant drop and magnetic rod techniques, respectively, were used. The dilatational analysis was performed in static and dynamic conditions, to obtain the equilibrium adsorption isotherms and the rheological parameters of the interfacial layers under both oscillation and stress relaxation. The interfaces were studied in shear conditions with small amplitude oscillations and creep tests. The obtained results evidenced that all tested proteins are able to build a strong viscoelastic layer with properties comparable to those of animal proteins. Brown rice protein seems particularly effective in reducing the interfacial tension even if shear tests evidence that the interface is weaker than that obtained using hemp or soy protein. Hemp protein seems very promising for potential practical uses yielding intermediate interfacial tensions and strong viscoelastic layers. [Display omitted] • Interfacial rheology of vegetable proteins at the sunflower oil/air interface was investigated. • Brown rice protein isolate seems particularly effective in reducing the interfacial tension and promoting emulsion formation. • Hemp protein isolate seems promising for potential practical uses because of its ability to bear destabilization phenomena. • Soy protein isolate shows an intermediate interfacial behavior between brown rice and hemp protein isolate. [ABSTRACT FROM AUTHOR]