Protein and lipid oxidation affect the viscoelasticity of whey protein layers at the oil–water interface

Abstract

Protein and lipid oxidation are prevailing issues that negatively affect the nutritional and sensory quality of food emulsions. It is probable that such oxidative modifications affect the functional properties of proteins, and in particular their ability to form densely packed, interconnected viscoelastic films at the oil–water interface. However, these aspects have hardly been investigated. We induced controlled levels of protein and lipid oxidation using whey protein solution and sunflower oil as substrates, respectively. The adsorption kinetics, surface activity, and dilatational interfacial rheology of whey proteins at the sunflower oil–water interface were investigated using a drop tensiometer. Both protein and lipid oxidation led to a decrease in interfacial elasticity compared to the non‐oxidized samples, though through different pathways: protein oxidation led to a broad range of proteinaceous species, including peptides and aggregates, which did not form an interconnected network. Lipid oxidation induced the formation of surface active compounds, which presumably formed segregated domains at the interface. Practical applications: Oxidative reactions prevent whey proteins to form strong, viscoelastic layers at the oil–water interface. This could, in turn, drastically affect their ability to stabilize food emulsions. These findings suggest that considering the initial oxidative state of ingredients should be an integral part of food emulsion formulation. Protein oxidation leads to the formation of a broad range of proteinasceous material, including peptides and aggregates. Lipid oxidation leads to the formation of surface‐active compounds. Both oxidative reactions decrease the ability of whey proteins to form interconnected, elastic interfacial layers at the oil–water interface.

Toward a Spatiotemporal Model of Oxidation in Lipid Dispersions: A Hypothesis‐Driven Review

“…This means that LOOHs are prone to accumulate at the lipid–water interface. Likewise, Berton‐Carabin et al . showed that oxidized stripped sunflower oil decreases the tension at the interface formed with water, while the parent non‐oxidized stripped oil does not.…”

Phenolic residues in spruce galactoglucomannans improve stabilization of oil-in-water emulsions

“…Moreover, oxidation causes physical changes to the emulsion structures, e.g., polymerization of lipids and eruption of emulsions. 12 Thus, lipids should be protected against oxidation, and at the same time, the interfacial structure may be protected. The rate of oxidation is dependent on the amount and type of oil, emulsifiers, and stabilizers, and on the partitioning of the emulsifier and stabilizer between the interface and continuous phase.…”

Oxidative and physical stability of oil-in-water emulsions prepared with quinoa and amaranth proteins

“…Additionally, advanced oxidative damage to proteins may lead to reduction in physical stability. It has been reported earlier that while moderate oxidation helps increase emulsifying activity of proteins, extensive oxidation weakens protein network at the interfacial layer and leads to lower emulsion stability through aggregation [48][49][50]. Higher physical stability of emulsions kept at 6 °C support this outcome.…”