Claire C. Berton-Carabin

Lipid Oxidation in Oil-in-Water Emulsions: Involvement of the Interfacial Layer

More polyunsaturated fats in processed foods and fewer additives are a huge demand of public health agencies and consumers. Consequently, although foods have an enhanced tendency to oxidize, the usage of antioxidants, especially synthetic antioxidants, is restrained. An alternate solution is to better control the localization of reactants inside the food matrix to limit oxidation. This review establishes the state-of-the-art on lipid oxidation in oil-in-water (O/W) emulsions, with an emphasis on the role of the interfacial region, a critical area in the system in that respect. We first provide a summary on the essential basic knowledge regarding (i) the structure of O/W emulsions and interfaces and (ii) the general mechanisms of lipid oxidation. Then, we discuss the factors involved in the development of lipid oxidation in O/W emulsions with a special focus on the role played by the interfacial region. The multiple effects that can be attributed to emulsifiers according to their chemical structure and their location, and the interrelationships between the parameters that define the physicochemistry and structure of emulsions are highlighted. This work sheds new light on the interpretation of reported results that are sometimes ambiguous or contradictory.

Pickering Emulsions for Food Applications: Background, Trends, and Challenges

Particle-stabilized emulsions, also referred to as Pickering emulsions, have garnered exponentially increasing interest in recent years. This has also led to the first food applications, although the number of related publications is still rather low. The involved stabilization mechanisms are fundamentally different as compared to conventional emulsifiers, which can be an asset in terms of emulsion stability. Even though most of the research on Pickering emulsions has been conducted on model systems, with inorganic solid particles, recent progress has been made on the utilization of food-grade or food-compatible organic particles for this purpose. This review reports the latest advances in that respect, including technical challenges, and discusses the potential benefits and drawbacks of using Pickering emulsions for food applications, as an alternative to conventional emulsifier-based systems.

Food-grade Micro-encapsulation Systems that May Induce Satiety via Delayed Lipolysis: A Review

ABSTRACT The increasing prevalence of overweight and obesity requires new, effective prevention and treatment strategies. One approach to reduce energy intake is by developing novel foods with increased satiating properties, which may be accomplished by slowing down lipolysis to deliver substrates to the ileum, thereby enhancing natural gut-brain signaling pathways of satiety that are normally induced by meal intake. To develop slow release food additives, their processing in the gastrointestinal tract has to be understood; therefore, we start from a general description of the digestive system and relate that to in vitro modeling, satiety, and lipolytic mechanisms. The effects of physicochemical lipid composition, encapsulation matrix, and interfacial structure on lipolysis are emphasized. We give an overview of techniques and materials used, and discuss partitioning, which may be a key factor for encapsulation performance. Targeted release capsules that delay lipolysis form a real challenge because of the high efficiency of the digestive system; hardly any proof was found that intact orally ingested lipids can be released in the ileum and thereby induce satiety. We expect that this challenge could be tackled with structured o/w-emulsion-based systems that have some protection against lipase, e.g., by hindering bile salt adsorption and/or delaying lipase diffusion.

Interfacial tension measured at high expansion rates and within milliseconds using microfluidics

To understand droplet formation and stabilisation, technologies are needed to measure interfacial tension at micrometer range and millisecond scale. In this paper, microtechnology is used, and that allows us to access these ranges and derive a model for surfactant free systems. The predicting power of the model was tested, and we found that it can be used to accurately (validated with >60 experiments) describe droplet size for a wide range of flow rates, interfacial tensions, and continuous phase viscosities. The model was used next to determine interfacial tensions in a system with hexadecane and sodium dodecylsulfate (SDS) solutions, and it was found that the model can be used for droplet formation times ranging from 0.4 to 9.4ms while using a wide range of process conditions. The method described here differs greatly from standard dynamic interfacial tension methods that use quiescent, mostly diffusion-limited situations. The effects that we measured are much faster due to enhanced mass transfer; this allows us to assess the typical time scales used in industrial emulsification devices.

Amadori products formation in emulsified systems

The formation of Amadori products (APs) is the key step determining the development of the Maillard reaction (MR). The information on the chemical behaviour of the reaction between amino acids and reducing sugars in emulsions during thermal treatments is scanty and mainly focused on volatile compounds. The aim of this work was to investigate the formation of APs from glucose and two amino acids with different partition coefficients (phenylalanine and leucine) in emulsions. Two submicron oil-in-water (O/W) emulsions consisting of water, tricaprylin and Tween 20 were prepared, thermally treated and the formation of fructose-phenylalanine (Fru-Phe) and fructose-leucine (Fru-Leu) was monitored by mass spectrometry. The concentration of Fru-Phe in submicron emulsions was similar to that in water, while Fru-Leu was reduced up to 47% in the emulsions. These data indicated that partition coefficient of amino acids, determining the reactants location, can substantially influence the MR and the final quality of foods.

Convective mass transport dominates surfactant adsorption in a microfluidic Y-junction

Surfactant adsorption during emulsification can be quantified by measuring the acting interfacial tension using a Y-junction microfluidic device. To obtain insight into the surfactant transport mechanism to the interface, the effect of shear force on the acting interfacial tension was assessed by systematically varying the continuous phase viscosity and velocity. Varying the continuous phase viscosity did not affect the acting interfacial tension, indicating that surfactant adsorption during Y-junction emulsification is not diffusion-limited. The acting interfacial tension was inversely dependent on the continuous phase velocity, which indicates that surfactant adsorption is governed by convective mass transfer resulting from the continuous phase velocity. The acting interfacial tension can be measured in the sub-millisecond time scale and under convective transport conditions using the Y-junction. These conditions are relevant to industrial emulsification and cannot be assessed by conventional tensiometry techniques (e.g., drop tensiometers) where surfactant adsorption is mostly driven by diffusion. We believe, therefore, that this method can be used to understand emulsifier adsorption during industrial emulsification, which can, in turn, be used to rationally design emulsion formulations and processes.

Encapsulation of the therapeutic microbe Akkermansia muciniphila in a double emulsion enhances survival in simulated gastric conditions

There is considerable attention for developing Akkermansia muciniphila as a new therapeutic microbe since it has shown to prevent diet-induced obesity and type 2 diabetes in mice. However, A. muciniphila is sensitive to gastric conditions such as low pH and oxygen. Therefore, we explored the possibility of encapsulating A. muciniphila in a water-in-oil-in-water (W/O/W) double emulsion, to allow for protection during gastric passage and subsequent release in the small intestine. The bacteria were efficiently encapsulated in the inner emulsion droplets and remained entrapped during in vitro gastric digestion. The cells were then released in the simulated intestinal phase of the in vitro system. The viability of encapsulated cells was found to be higher when compared to cells dispersed in buffer, that had been subjected to similar mechanical process as the one conducted to prepare the emulsion systems. Surprisingly, the viability of the processed cells was even higher than that of the cells dispersed in buffer without processing, likely due to shear-induced stress tolerance. To conclude, encapsulation in a double emulsion seems to be a promising strategy to protect A. muciniphila during gastric passage in oral formulations.

Emulsification: Established and Future Technologies

Oil and water don’t mix, that is what everyone knows….but if you are able to convince them; it is very well possible to produce stable emulsions. For this you need the right technology, of which examples will be presented in this chapter, focusing both on established equipment (high pressure homogenization, rotor-stator systems, ultrasound) and technology that is currently developed (microfluidic technology, hybrid systems). Based on the droplet size that is generated and the energy that is required to do so, the technologies will be compared. Besides, attention is given to the emulsion ingredients that stabilize the oil-water interface, and prevent instability of the emulsion through sedimentation, flocculation, and/or coalescence. The chapter concludes with a short outlook on methods that are currently developed to determine emulsion stability, which we expect to become very useful, not only for emulsions but also for derived products.

Ionic Liquids in the Synthesis of Antioxidant Targeted Compounds

Abstract Oxidation of polyunsaturated lipids is a major cause of degradation of the sensory and nutritional quality of food products. The oxidation reactions lead to formation of volatile compounds generally associated with unpleasant flavors, which damages the sensory quality of foods. Lipid oxidation is also responsible for a loss of macro- and micronutrients, and leads to the formation of potentially toxic compounds. The interest in using antioxidants from natural sources is increasing, and ionic liquids (ILs) have attracted considerable attention as solvents in extraction and separation of antioxidants from natural materials. Additionally, ILs are also applied as reaction media for the lipophilization of natural antioxidant. Lipophilization of antioxidants improve the oil solubility and tailor the antioxidants to specific applications, according to the polar paradox and cutoff theories.

Protein Oxidation in Plant Protein-Based Fibrous Products: Effects of Encapsulated Iron and Process Conditions

Plant protein-based fibrous structures have recently attracted attention because of their potential as meat replacer formulations. It is, however, unclear how the process conditions and fortification with micronutrients may affect the chemical stability of such products. Therefore, we aimed to investigate the effects of process conditions and the incorporation of iron (free and encapsulated) on protein oxidation in a soy protein-based fibrous product. First, the physicochemical stability of iron-loaded pea protein particles, used as encapsulation systems, was investigated when exposed to 100 or 140 °C. Second, protein oxidation was measured in the iron-fortified soy protein-based fibrous structures made at 100 or 140 °C. Exposure to high temperatures increased the carbonyl content in pea protein particles. The incorporation of iron (free or encapsulated) did not affect carbonyl content in the fibrous product, but the process conditions for making such products induced the formation of carbonyls to a fairly high extent.