Search

Lipid oxidation constitutes the main source of degradation of lipid-rich foods, including food emulsions. The complexity of the reactions at play combined with the increased demand from consumers for less processed and more natural foods result in additional challenges in controlling this phenomenon. This review provides an overview of the insights acquired over the past two decades on the understanding of lipid oxidation in oil-in-water (O/W) emulsions. After introducing the general structure of O/W emulsions and the classical mechanisms of lipid oxidation, the contribution of less studied oxidation products and the spatiotemporal resolution of these reactions will be discussed. We then highlight the impact of emulsion formulation on the mechanisms, taking into consideration the new trends in terms of emulsifiers as well as their own sensitivity to oxidation. Finally, novel antioxidant strategies that have emerged to meet the recent consumer's demand will be detailed. In an era defined by the pursuit of healthier, more natural, and sustainable food choices, a comprehensive understanding of lipid oxidation in emulsions is not only an academic quest, but also a crucial step towards meeting the evolving expectations of consumers and ensuring the quality and stability of lipid-rich food products., Competing Interests: Declaration of competing interest JvD is employed by a company (Unilever) that manufactures and markets food emulsions., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Dietary lipids containing high concentrations of polyunsaturated fatty acids are considered to be beneficial to human health, yet their incorporation within formulated foods is complicated by their susceptibility to oxidation. Lipid oxidation in foods is inhibited through the incorporation of antioxidants, yet the list of antioxidants approved for food use is small, and consumers frequently demand foods without synthetic additives. As a consequence, food processors are now tasked with improving the efficacy of approved, "natural" (i.e., nonsynthetic) antioxidants; a rational strategy for doing so involves localizing the antioxidants at the interface where oxidation usually occurs and regenerating the consumed antioxidants after the oxidation event has occurred. The present study describes a procedure to evaluate antioxidant interactions in oil-in-water food emulsions, which is based on controlled oxidation reactions induced in the dispersed oil phase by the lipophilic radical generator, 2,2'-azobis(2,4-dimethylvaleronitrile). The extent of lipid oxidation is measured spectroscopically by following the loss of an oxidatively labile, lipophilic probe (methyl eleostearate), the synthesis of which is described here. Using this procedure, the ability of various aqueous phase solvated antioxidants (ascorbic acid, gallic acid, (-)-epicatechin, (-)-epigallocatechin-3-gallate) to regenerate lipid phase solvated α-tocopherol was evaluated. In all cases, the test compounds were able to inhibit oxidation reactions; however, these effects were not profoundly synergistic, and the maximum synergistic interaction observed was only ∼ 3% using ascorbic acid.

Lipid oxidation is a major cause of quality deterioration in food products. In these foods, lipids are often present in a bulk or in emulsified forms. In both systems, the rate, extent and pathway of oxidation are highly dependent on the presence of colloidal structures and interfaces because these are the locations where oxidation normally occurs. In bulk oils, reverse micelles (association colloids) are present and are believed to play a crucial role on lipid oxidation. Conversely, in emulsions, surfactant micelles are present that also play a major role in lipid oxidation pathways. After a brief description of lipid oxidation and antioxidants mechanisms, this review discusses the current understanding of the influence of micellar structures on lipid oxidation. In particular, is discussed the major impact of the presence of micelles in emulsions, or reverse micelles (association colloids) in bulk oil on the oxidative stability of both systems. Indeed, both micelles in emulsions and associate colloids in bulk oils are discussed in this review as nanoscale structures that can serve as reservoirs of antioxidants and pro-oxidants and are involved in their transport within the concerned system. Their role as nanoreactors where lipid oxidation reactions occur is also commented. [ABSTRACT FROM AUTHOR]

The encapsulation β-carotene in whey protein concentrate (WPC) capsules through the emulsion electrospraying technique was studied, using deep eutectic solvents (DES) as solvents. These novel solvents are characterized by negligible volatility, a liquid state far below 0 °C, a broad range of polarity, high solubilization power strength for a wide range of compounds, especially poorly water-soluble compounds, high extraction ability, and high stabilization ability for some natural products. Four DES formulations were used, based on mixtures of choline chloride with water, propanediol, glucose, glycerol, or butanediol. β-Carotene was successfully encapsulated in a solubilized form within WPC capsules; as a DES formulation with choline chloride and butanediol, the formulation produced capsules with the highest carotenoid loading capacity. SEM micrographs demonstrated that round and smooth capsules with sizes around 2 µm were obtained. ATR-FTIR results showed the presence of DES in the WPC capsules, which indirectly anticipated the presence of β-carotene in the WPC capsules. Stability against photo-oxidation studies confirmed the expected presence of the bioactive and revealed that solubilized β-carotene loaded WPC capsules presented excellent photo-oxidation stability compared with free β-carotene. The capsules developed here clearly show the significant potential of the combination of DES and electrospraying for the encapsulation and stabilization of highly insoluble bioactive compounds. [ABSTRACT FROM AUTHOR]

Many previous reports suggested that conventional antioxidant assays could not forecast antioxidant performance of plant extracts, especially when it came to a real food system such as oil‐in‐water emulsion. In this study, antioxidant activities of aqueous and ethanolic plant extracts are investigated using multiple conventional assays (TPC, ABTS, FRAP, ORAC) and the oil‐in‐water (O/W) emulsion‐based high throughput assays (the CAT and ApoCAT) in a comparison with an autoxidative O/W emulsion model monitored by formation of lipid hydroperoxide and TBARS values. Results suggest that only the ApoCAT assay is able to forecast the antioxidative performances of the extracts in O/W emulsions, regardless of the differences in extraction solvents, while the CAT assay can explain only the performance of ethanolic plant extracts in O/W emulsions. According to untargeted metabolite analysis, the antioxidants activities of plant extracts might be strongly influenced by extraction solvents. As a result, not only is the quantity of particular metabolites impacted, but also the whole metabolite (antioxidant) profiles of the extracts are modified. In addition, this study demonstrates that both the chemical reaction scheme and physical‐state of a model are important parameters for designing a better antioxidant assay in the future. Practical Applications: The ApoCAT assay would be a more practical method for screening antioxidant compounds and/or crude plant extracts than conventional antioxidant assays and the original CAT assay. The antioxidant capacity of plant extracts obtaining from the ApoCAT can be used to represent their antioxidant performances in food emulsions regardless of their extraction solvents. Several crude plant extracts using different solvents are used to validate the performance of the CAT and the ApoCAT assays in comparisons with multiple conventional antioxidant assays. These assays differ from each other in terms of scheme of reaction and physical state of the test. In addition, oil‐in‐water (O/W) emulsion model is used as a reference method representing the antioxidant activities in food matrices. Principal component analysis (PCA) is performed to better understand the relationship among all assays. The results suggest that only the ApoCAT assay exhibits a close relationship with O/W emulsion model in both crude ethanolic and aqueous plant extracts. Furthermore, putative metabolite profiles of crude plant extracts are identified using LC‐orbitrap MS/MS. Several crude plant extracts using different solvents are used to validate the performance of the CAT and the ApoCAT assays in comparisons with multiple conventional antioxidant assays. These assays differ from each other in terms of scheme of reaction and physical state of the test. In addition, oil‐in‐water (O/W) emulsion model is used as a reference method representing the antioxidant activities in food matrices. Principal component analysis (PCA) is performed to better understand the relationship among all assays. The results suggest that only the ApoCAT assay exhibits a close relationship with O/W emulsion model in both crude ethanolic and aqueous plant extracts. Furthermore, putative metabolite profiles of crude plant extracts are identified using LC‐orbitrap MS/MS. [ABSTRACT FROM AUTHOR]

• We studied how phenolipid polarity affects antioxidant activity in dried emulsions. • Polar antioxidants (e.g., gallic acid) are not effective in spray-dried emulsions. • For both the surface and encapsulated fat, octyl gallate seems to be most effective. • Yet, dodecyl and hexadecyl gallates are both still relatively effective. • The onset of lipid oxidation occurs during the spray drying process. Lipid oxidation is a well-recognized issue in dried food emulsions, such as infant milk formula. Antioxidants can be used to mitigate this issue; however, their efficiency in such complex systems is far from understood. In this study, antioxidant polarity is varied through the alkyl chain length of gallic acid esters (0–16 carbon atoms) incorporated to O/W emulsions that are subsequently spray-dried. During processing and subsequent storage of the samples, antioxidants with more than eight carbon atoms are effective. Both for encapsulated fat and surface free fat, we observe a slight cut-off effect, meaning that beyond eight alkyl groups, a more nonpolar antioxidant is slightly less effective. Depending on the antioxidant polarity, lipid oxidation is faster either in the encapsulated or in the surface free fat. The insights obtained contribute to understanding lipid oxidation in low moisture food emulsions, and thus lead to effective antioxidant strategies. [ABSTRACT FROM AUTHOR]

The effect of the presence of surfactant micelles and of the mode of incorporation (pre-homogenization or post-homogenization) on the antioxidant efficiency of a homologous series of n-alkyl gallates phenolipids (G0, G3, G8, G12 or G16) was investigated in oil-in-water nanoemulsions. In both absence and presence of surfactant micelles, G12 and G16 were the best antioxidants. The effect of the mode of incorporation was modulated by the presence of surfactant micelles. In absence of surfactant micelles, G8 and G16 had higher efficiency when incorporated pre-homogenization, suggesting that the mode of incorporation promoted a distinct initial distribution of these compounds. In contrast, in presence of surfactant micelles, the antioxidants could be incorporated in any phases without efficiency loss. These results demonstrate the important role of surfactant micelles in modulating the antioxidant efficiency and could be used by the food industry to optimize emulsion formulations. • Alkyl gallates varying in chain lengths were investigated for their antioxidant efficiency in oil-in-water emulsion. • The mode of incorporation influences their activity to protect lipids from oxidation. • Interactions between antioxidant and emulsifier micelles modify antioxidants behavior. • Effect of the mode of incorporation was less important in the presence of surfactant micelles. [ABSTRACT FROM AUTHOR]