Destabilization of multilayered interfaces in digestive conditions limits their ability to prevent lipolysis in emulsions

Effects of mixing ratio on physicochemical, structural properties and application in lycopene-loaded emulsions of blends of whey protein and pea protein

Physicochemical, structural properties and application in lycopene-loaded emulsions of blends of whey protein isolate (WPI) and pea protein isolate (PPI) at varying mass ratios (100/0, 75/25, 50/50, 25/75, 0/100) were investigated. Data indicated that the mass ratios affected the physical, chemical and storage stability of the emulsion by influencing the particle size, zeta-potential, surface hydrophobicity, free sulfhydryl content, and secondary structure of the blends. Particularly, emulsion with a mixing ratio of 75/25 exhibited superior physical stability against salt concentrations (200 and 500 mM), better chemical stability against UV light and heat, and maintained stability over a 30-day storage period. Emulsions stabilized by blends of different ratios exhibited similar digestion behavior, with no significant differences observed in lycopene's transformation stability and bio-accessibility. Data indicated that substitution of whey protein by pea protein is effective in term of emulsifier application and replacement ratio is an important factor need to be considered.

The non-covalent and covalent interactions of whey proteins and saccharides: influencing factor and utilization in food

During the application of Whey proteins (WPs), they often have complex interactions with saccharides (Ss), another important biopolymer in food substrate. The texture and sensory qualities of foods containing WPs and Ss are largely influenced by the interactions of WPs-Ss. Moreover, the combination of WPs and Ss is possible to produce many excellent functional properties including emulsifying properties and thermal stability. However, the interactions between WPs-Ss are complex and susceptible to some processing conditions. In addition, with different interaction ways, they can be applied in different fields. Therefore, the non-covalent interaction mechanisms between WPs-Ss are firstly summarized in detail, including electrostatic interaction, hydrogen bond, hydrophobic interaction, van der Waals force. Furthermore, the existence modes of WPs-Ss are introduced, including complex coacervates, soluble complexes, segregation, and co-solubility. The covalent interactions of WPs-Ss in food applications are often formed by Maillard reaction (dry or wet heat reaction) and occasionally through enzyme induction. Then, two common influencing factors, pH and temperature, on non-covalent/covalent bonds are introduced. Finally, the applications of WPs-Ss complexes and conjugations in improving WP stability, delivery system, and emulsification are described. This review can improve our understanding of the interactions between WPs-Ss and further promote their wider application.

A review of recent progress in improving the bioavailability of nutraceutical-loaded emulsions after oral intake

Increasing awareness of the health benefits of specific constituents in fruits, vegetables, cereals, and other whole foods has sparked a broader interest in the potential health benefits of nutraceuticals. Many nutraceuticals are hydrophobic substances, which means they must be encapsulated in colloidal delivery systems. Oil-in-water emulsions are one of the most widely used delivery systems for improving the bioavailability and bioactivity of these nutraceuticals. The composition and structure of emulsions can be designed to improve the water dispersibility, physicochemical stability, and bioavailability of the encapsulated nutraceuticals. The nature of the emulsion used influences the interfacial area and properties of the nutraceutical-loaded oil droplets in the gastrointestinal tract, which influences their digestion, as well as the bioaccessibility, metabolism, and absorption of the nutraceuticals. In this article, we review recent in vitro and in vivo studies on the utilization of emulsions to improve the bioavailability of nutraceuticals. The findings from this review should facilitate the design of more efficacious nutraceutical-loaded emulsions with increased bioactivity.

Palm Lipid Emulsion Droplet Crystallinity and Gastric Acid Stability in Relation to in vitro Bioaccessibility and in vivo Gastric Emptying

It is poorly understood how the physical state of emulsified triacylglycerol (TAG) alters colloidal behavior in the gastrointestinal tract to modulate lipid digestion and absorption. We, therefore, aimed to investigate the individual and combined effects on fatty acid (FA) bioaccessibility using the dynamic TIM-1 in vitro digestion model and integrate the results with those from a human clinical study. Four 20% oil-in-water emulsions with overlapping particle size distributions contained either partially crystalline solid (palm stearin) or liquid (palm olein) lipid droplets at 37°C and either the colloidally acid-stable Tween 80 (2.2%) or acid-unstable Span 60 (2.5%) emulsifier. Experimental meals were fed to the TIM-1, and jejunal and ileal dialysates were analyzed over 6 h to measure free FA concentration. Cumulative FA bioaccessibility was significantly higher for the liquid stable emulsion compared to all others (p < 0.05), which did not differ (p > 0.05). Emulsified TAG physical state was associated with differences in overall bioaccessibility (higher for liquid state TAG) in the colloidally stable emulsions, but this difference was blunted in droplets susceptible to acidic flocculation. In contrast, human postprandial TAG concentrations did not differ significantly between the emulsions. The discrepancy may relate to differences in in vivo gastric emptying (GE) as evidenced by ultrasonography. When the in vivo differences in GE were accounted for in follow-up TIM-1 experiments, the findings aligned more closely. Cumulative FA bioaccessibility for the liquid stable emulsion no longer differed significantly from the other emulsions, and SU’s bioaccessibility was the lowest, consistent with the in vivo observations. This work highlights the potential for TAG physical state and colloidal stability to interactively alter behavior in the gastrointestinal tract with implications for FA absorption, and the importance of establishing and improving in vitro–in vivo correlations in food-nutrition research.

Effect of the chitosan second layer on the gelation and controlled digestion of Citrem-chitosan bilayer emulsions

This research aimed to induce repulsive gelation in Citrem-stabilized O/W emulsions by creating a secondary layer of chitosan around the droplets. A range of chitosan concentrations (0-0.25 wt%) and degrees of deacetylation (DDA 50% and 93%) were used to establish the conditions for repulsive gelation in 36 wt% O/W emulsion. The bilayer emulsions were prepared by the electrostatic deposition of positively charged chitosan on negatively charged Citrem-stabilized droplets at pH 4. The droplet size increased from <0.5 μm for the primary emulsion to 5-10 μm at an intermediate chitosan concentration (0.05-0.15 wt%) due to bridging flocculation and again dropped to 1.7-3.6 μm at higher concentrations (0.2 and 0.25 wt%). The droplet charge changed from -48 mV for the primary emulsion to +41.4 and +54.5 mV after surface saturation by DDA 50 and DDA 93 chitosan, respectively. The strain and frequency-dependent rheology indicated that with an increase in the chitosan concentration, emulsions changed from a viscoelastic liquid for monolayer emulsions to strong attractive gel due to bridging flocculation at an intermediate chitosan concentration. At a higher concentration, repulsive gels were formed at complete coverage due to an increase in the effective oil volume fraction towards close packing resulting from the expansion of the interfacial steric barrier and charge cloud thickness. The overall lipid digestibility during in vitro digestion was 25.7% for monolayer emulsions, which decreased with increased chitosan concentration and reached the lowest at surface saturation (17.5%). It was proposed that the formation of the Citrem-chitosan bilayer controlled lipid digestibility by delaying the action of gastric and pancreatic lipases. Such bilayer emulsion gels can be utilized for structure formation in reduced-fat foods.

Biophysical insights into modulating lipid digestion in food emulsions

During the last decade, major scientific advances on understanding the mechanisms of lipid digestion and metabolism have been made, with a view to addressing health issues (such as obesity) associated with overconsumption of lipid-rich and sucrose-rich foods. As lipids in common foods exist in the form of emulsions, the structuring of emulsions has been one the main strategies for controlling the rate of lipid digestion and absorption, at least from a colloid science viewpoint. Modulating the kinetics of lipid digestion and absorption offers interesting possibilities for developing foods that can provide control of postprandial lipaemia and control the release of lipophilic compounds. Food emulsions can be designed to achieve considerable differences in the kinetics of lipid digestion but most research has been applied to relatively simple model systems and in in vitro digestion models. Further research to translate this knowledge into more complex food systems and to validate the results in human studies is required. One promising approach to delay/control lipid digestion is to alter the stomach emptying rate of lipids, which is largely affected by interactions of emulsion droplets with the food matrices. Food matrices with different responses to the gastric environment and with different interactions between oil droplets and the food matrix can be designed to influence lipid digestion. This review focuses on key scientific advances made during the last decade on understanding the physicochemical and structural modifications of emulsified lipids, mainly from a biophysical science perspective. The review specifically explores different approaches by which the structure and stability of emulsions may be altered to achieve specific lipid digestion kinetics.

Physiological fluid interfaces: Functional microenvironments, drug delivery targets, and first line of defense

Fluid interfaces, i.e. the boundary layer of two liquids or a liquid and a gas, play a vital role in physiological processes as diverse as visual perception, oral health and taste, lipid metabolism, and pulmonary breathing. These fluid interfaces exhibit a complex composition, structure, and rheology tailored to their individual physiological functions. Advances in interfacial thin film techniques have facilitated the analysis of such complex interfaces under physiologically relevant conditions. This allowed new insights on the origin of their physiological functionality, how deviations may cause disease, and has revealed new therapy strategies. Furthermore, the interactions of physiological fluid interfaces with exogenous substances is crucial for understanding certain disorders and exploiting drug delivery routes to or across fluid interfaces. Here, we provide an overview on fluid interfaces with physiological relevance, namely tear films, interfacial aspects of saliva, lipid droplet digestion and storage in the cell, and the functioning of lung surfactant. We elucidate their structure-function relationship, discuss diseases associated with interfacial composition, and describe therapies and drug delivery approaches targeted at fluid interfaces. STATEMENT OF SIGNIFICANCE: Fluid interfaces are inherent to all living organisms and play a vital role in various physiological processes. Examples are the eye tear film, saliva, lipid digestion & storage in cells, and pulmonary breathing. These fluid interfaces exhibit complex interfacial compositions and structures to meet their specific physiological function. We provide an overview on physiological fluid interfaces with a focus on interfacial phenomena. We elucidate their structure-function relationship, discuss diseases associated with interfacial composition, and describe novel therapies and drug delivery approaches targeted at fluid interfaces. This sets the scene for ocular, oral, or pulmonary surface engineering and drug delivery approaches.

Advances of plant-based structured food delivery systems on the in vitro digestibility of bioactive compounds

Food researchers are currently showing a growing interest in in vitro digestibility studies due to their importance for obtaining food products with health benefits and ensuring a balanced nutrient intake. Various bioactive food compounds are sensitive to the digestion process, which results in a lower bioavailability in the gut. The main objective of structured food delivery systems is to promote the controlled release of these compounds at the desired time/place, in addition to protecting them during digestion processes. This review provides an overview of the influence of structured delivery systems on the in vitro digestive behavior. The main delivery systems are summarized, the pros and cons of different structures are outlined, and examples of several studies that optimized the use of these structured systems are provided. In addition, we have reviewed the use of plant-based systems, which have been of interest to food researchers and the food industry because of their health benefits, improved sustainability as well as being an alternative for vegetarian, vegan and consumers suffering from food allergies. In this context, the review provides new insights and comprehensive knowledge regarding the influence of plant-based structured systems on the digestibility of encapsulated compounds and proteins/polysaccharides used in the encapsulation process.

Cellulose and cellulose derivatives: Different colloidal states and food-related applications

Development of new sources and isolation processes has recently enhanced the production of cellulose in many different colloidal states. Even though cellulose is widely used as a functional ingredient in the food industry, the relationship between the colloidal states of cellulose and its applications is mostly unknown. This review covers the recent progress on illustrating various colloidal states of cellulose and the influencing factors with special emphasis on the correlation between the colloidal states of cellulose and its applications in food industry. The associated unique colloidal states of cellulose like high aspect ratio, crystalline structure, surface charge, and wettability not only promote the stability of colloidal systems, but also help improve the nutritional aspects of cellulose by facilitating its interactions with digestive system. Further studies are required for the rational control and improvement of the colloidal states of cellulose and producing food systems with enhanced functional and nutritional properties.

Microtechnological Tools to Achieve Sustainable Food Processes, Products, and Ingredients

One of the major challenges we face as humankind is supplying a growing world population with sufficient and healthy foods. Although from a worldwide perspective sufficient food is produced, locally, the situation can be dire. Furthermore, the production needs to be increased in a sustainable manner for future generations, which also implies prevention of food waste, and making better use of the available resources. How to contribute to this as food technologists is an ultimate question, especially since the tools that can investigate processes at relevant time scales, and dimensions, are lacking. Here we propose the use of microtechnology and show examples of how this has led to new insights in the fields of ingredient isolation (filtration), and emulsion/foam formation, which will ultimately lead to better-defined products. Furthermore, microfluidic tools have been applied for testing ingredient functionality, and for this, various examples are discussed that will expectedly contribute to making better use of more sustainably sourced starting materials (e.g., novel protein sources). This review will wrap up with a section in which we discuss future developments. We expect that it will be possible to link food properties to the effects that foods create in vivo. We thus expand the scope of this review that is technical in nature, toward physiological functionality, and ultimately to rational food design that is targeted to improve human health.

Bioaccessibility of Lipophilic Compounds Vehiculated in Emulsions: Choice of Lipids and Emulsifiers

Great efforts have been made to design emulsions considering the need to perform an effective encapsulation, protection, vehiculation, and bioaccessibility of lipophilic compounds. This task can be achieved by manipulating the structure of the emulsion based on the choice of the processes and ingredients of the aqueous phase, interface, and lipid matrix. Thus, the main focus of this perspective is to provide insights into the use of ingredient engineering in manipulating/building emulsion structures that enhance lipophilic compound release and bioaccessibility.

In Vitro Digestion of Oil-in-Water Emulsions Stabilized by Regenerated Chitin

Regenerated chitin (R-chitin) can stabilize oil-in-water (O/W) emulsions containing up to 50% oil at a low chitin dosage of 2 mg/g oil. The mean droplet size of the resulting emulsion decreased as more R-chitin was used. Confocal laser scanning microscopy (CLSM) demonstrated the adsorption of R-chitin on emulsion droplets surface, confirming the emulsions were stabilized via Pickering mechanism. The effects of R-chitin concentration on storage stability, microstructure, and lipid digestion properties were investigated. Pickering emulsions stabilized by R-chitin above 1.0% w/w exhibited outstanding physical stability against coalescence and Ostwald ripening. In particular, highly consistent emulsions that remained almost unchanged during oral, gastric, and intestine digestion could be prepared using R-chitin. The emulsions could enhance fullness and satiety perceptions at gastric level, and R-chitin could be used as a substitute for food emulsifiers for weight management via increasing satiation perception and reducing lipid digestion.

Reducing Intestinal Digestion and Absorption of Fat Using a Nature-Derived Biopolymer: Interference of Triglyceride Hydrolysis by Nanocellulose

Engineered nanomaterials are increasingly added to foods to improve quality, safety, or nutrition. Here we report the ability of ingested nanocellulose (NC) materials to reduce digestion and absorption of ingested fat. In the small intestinal phase of an acellular simulated gastrointestinal tract, the hydrolysis of free fatty acids (FFA) from triglycerides (TG) in a high-fat food model was reduced by 48.4% when NC was added at 0.75% w/w to the food, as quantified by pH stat titration, and by 40.1% as assessed by fluorometric FFA assay. Furthermore, translocation of TG and FFA across an in vitro cellular model of the intestinal epithelium was significantly reduced by the presence of 0.75% w/w NC in the food (TG by 52% and FFA by 32%). Finally, in in vivo experiments, the postprandial rise in serum TG 1 h after gavage with the high fat food model was reduced by 36% when 1.0% w/w NC was administered with the food. Scanning electron microscopy and molecular dynamics studies suggest two primary mechanisms for this effect: (1) coalescence of fat droplets on fibrillar NC (CNF) fibers, resulting in a reduction of available surface area for lipase binding and (2) sequestration of bile salts, causing impaired interfacial displacement of proteins at the lipid droplet surface and impaired solubilization of lipid digestion products. Together these findings suggest a potential use for NC, as a food additive or supplement, to reduce absorption of ingested fat and thereby assist in weight loss and the management of obesity.