Isolation and characterization of nettle (Urtica dioica L.) seed proteins: Conversion of underutilized by-products of the edible oil industry into food emulsifiers.

This study aimed to upcycle a byproduct of the edible oil industry, cold-pressed nettle seed meal (CPNSM), into a plant-based emulsifier, thereby increasing the sustainability of the food system. The protein content of the nettle seed protein (NSP) powder was 48.3% with glutamic acid (16.6%), asparagine (10.7%), and arginine (9.7%) being the major amino acids. NSPs had a denaturation temperature of 66.6 °C and an isoelectric point of pH 4.3. They could be used as emulsifiers to form highly viscous coarse corn oil-in-water emulsions (10% oil, 4% NSP). Nevertheless, 10-fold diluted emulsions exhibited rapid creaming under different pH (2-9), salt (0-500 mM NaCl) and temperature (>40 °C) conditions, but they were relatively stable to aggregation. Our findings suggest that NSPs could be used as emulsifiers in highly viscous or gelled foods, like dressings, sauces, egg, cheese, or meat analogs.

Development of plant-based whole egg analogs using emulsion technology.

RuBisCO is a plant protein that can be derived from abundant and sustainable natural resources (such as duckweed), which can be used as both an emulsifying and gelling agent. Consequently, it has the potential to formulate emulsion gels that can be used for the development of plant-based replacements of whole eggs. In this study, we investigated the ability of RuBisCO-based emulsion gels to mimic the desirable properties of whole eggs. The emulsion gels contained 12.5 wt% RuBisCO and 10 wt% corn oil to mimic the macronutrient composition of real whole eggs. Initially, an oil-in-water emulsion was formed, which was then heated to convert it into an emulsion gel. The impact of oil droplet diameter (∼15, 1, and 0.2 µm) on the physicochemical properties of the emulsion gels was investigated. The lightness and hardness of the emulsion gels increased as the droplet size decreased, which meant that their appearance and texture could be modified by controlling droplet size. Different concentrations of curcumin (3, 6, and 9 mg/g oil) were incorporated into the emulsions using a pH-driven approach. The curcumin was used as a natural dual functional ingredient (colorant and nutraceutical). The yellow-orange color of curcumin allowed us to match the appearance of raw and cooked whole eggs. This study shows that whole egg analogs can be formulated using plant-based emulsion gels containing natural pigments.

Influence of pH and ionic strength on the physicochemical and structural properties of soybean ß-conglycinin subunits in aqueous dispersions.

Understanding the impact of pH and ionic strength on the physicochemical and structural properties of soy proteins at subunit level is essential for design and fabrication of many plant-based foods. In this study, soybean ß-conglycinin and its subunit fractions αα' and ß were dispersed in solutions with different pH values (3.7, 7.6, and 9.0) at low (5 mM NaCl) and high (400 mM NaCl) ionic strengths, respectively. The solubility, rheology, particle size, zeta potential, microstructure, secondary structure, and tertiary structure of the different dispersions were analyzed using a range of analytical methods. The ß-conglycinin, αα'- and ß-subunits aggregated near the isoelectric point (pH 3.7). Increasing the ionic strength led to the assembly of more homogeneous units. An increase in ionic strength at pH 7.6 and pH 9.0 led to electrostatic screening, which promoted dissociation of the aggregates. The ß-subunit showed a greater sensitivity to pH and ionic strength than the αα'-subunits. Based on the evidence from a range of analytical methods, the highly hydrophilic extension region of the αα'-subunits played an important role in determining the stability of the ß-conglycinin dispersions under different environmental conditions. Moreover, the N-linked glycans appeared to impact the conformation and aggregation state of the ß-conglycinin.

Optimizing Protein Fiber Spinning to Develop Plant-Based Meat Analogs via Rheological and Physicochemical Analyses.

The substitution of meat products in the human diet with plant-based analogs is growing due to environmental, ethical, and health reasons. In this study, the potential of fiber-spinning technology was explored to spin protein fiber mimicking the structural element of meat muscle for the purpose of developing plant-based meat analogs. Overall, this approach involved extruding fine fibers and then assembling them into hierarchical fibrous structures resembling those found in whole muscle meat products. Considering the nutritional facts and to help build muscle fiber, soy protein, polysaccharide (pectin, xanthan gum, or carrageenan), plasticizer (glycerol), and water were used in the formulations to spin into fibers using an extruder with circular orifice dies. Extrudability and thermal and rheological properties were assessed to characterize the properties of the spun fiber. The extrusion trials showed that the presence of the polysaccharides increased the cohesiveness of the fibers. The properties of the fibers produced also depended on the temperature used during extrusion, varying from pasty gels to elastic strands. The extrudability of the fibers was related to the rheological properties (tan δ) of the formulations. This study demonstrated that fiber-spinning technology can be used to produce fibrous materials from plant-derived ingredients. However, the formulation and operating conditions must be optimized to obtain desirable physicochemical and functional attributes in the fibers produced.

Post pH-driven encapsulation of polyphenols in next-generation foods: principles, formation and applications.

To meet the needs of a growing global population (∼10 billion by 2050), there is an urgent demand for sustainable, healthy, delicious, and affordable next-generation foods. Natural polyphenols, which are abundant in edible plants, have emerged as promising food additives due to their potential health benefits. However, incorporating polyphenols into food products presents various challenges, including issues related to crystallization, low water-solubility, limited bioavailability, and chemical instability. pH-driven or pH-shifting approaches have been proposed to incorporate polyphenols into the delivery systems. Nevertheless, it is unclear whether they can be generally used for the encapsulation of polyphenols into next-generation foods. Here, we highlight a post pH-driven (PPD) approach as a viable solution. The PPD approach inherits several advantages, such as simplicity, speed, and environmental friendliness, as it eliminates the need for heat, organic solvents, and complex equipment. Moreover, the PPD approach can be widely applied to different polyphenols and food systems, enhancing its versatility while also potentially contributing to reducing food waste. This review article aims to accelerate the implementation of the PPD approach in the development of polyphenol-fortified next-generation foods by providing a comprehensive understanding of its fundamental principles, encapsulation techniques, and potential applications in plant-based foods.

Intrinsic structures and properties of polyphenols are introduced.Fundamental principles of the PPD approach are emphasized.Potential factors to affect the encapsulation efficiency of polyphenols are discussed.It has many promising applications in creating polyphenols-fortified foods or ingredients.

Co-Encapsulation of Multiple Polyphenols in Plant-Based Milks: Formulation, Gastrointestinal Stability, and Bioaccessibility.

Plant-based milk is particularly suitable for fortification with multiple nutraceuticals because it contains both hydrophobic and hydrophilic domains that can accommodate molecules with different polarities. In this study, we fortified soymilk with three common polyphenols (curcumin, quercetin, and resveratrol) using three pH-driven approaches. We compared the effectiveness of these three different approaches for co-encapsulating polyphenols. The gastrointestinal fate of the polyphenol-fortified soymilks was then studied by passing them through a simulated mouth, stomach, and small intestine, including the stability and bioaccessibility of polyphenols. All three pH-driven approaches were suitable for co-encapsulating multiple polyphenols at a high encapsulation efficiency, especially for the curcumin and resveratrol. The polyphenol-loaded delivery systems exhibited similar changes in particle size, charge, stability, and bioaccessibility as they passed through the mouth, stomach, and intestinal phases. The bioaccessibility of the co-encapsulated polyphenols was much greater than that of crystallized polyphenols dispersed in water. The poor bioaccessibility of the crystallized polyphenols was attributed to their low solubility in water, which made them more difficult to solubilize within mixed micelles. This study underscores the feasibility of pH-driven approaches for encapsulating a variety of polyphenols into the same plant-based delivery system. These fortified plant-based milks may therefore be designed to provide specific health benefits to consumers.

Applications of the INFOGEST In Vitro Digestion Model to Foods: A Review.

The in vitro digestion model developed by the INFOGEST international consortium is widely used to simulate the physicochemical processes occurring inside the human gastrointestinal tract (mouth, stomach, and small intestine) during the digestion of foods. In this review, we provide a brief overview of the INFOGEST method and the procedures used to measure the digestion of macronutrients (lipids, proteins, and starch), the bioaccessibility of bioactive agents (vitamins, minerals, and nutraceuticals), and the changes in the structure and physical properties of foods under gastrointestinal conditions (particle size, charge, and location). We then review the application of the INFOGEST method for monitoring the gastrointestinal fate of different kinds of foods and beverages, including dairy, egg, meat, seafood, fruit, vegetable, cereal, and emulsified products. We also discuss the application of this method for studying the digestibility of next-generation plant-based foods, such as meat, seafood, dairy, and egg analogs. Finally, the benefits and limitations of this standardized in vitro digestion model are assessed.

Formulation and characterization of plant-based egg white analogs using RuBisCO protein.

RuBisCO protein, which can be isolated from abundant and sustainable plant sources, can mimic some of the desirable functional attributes of egg white proteins. In this study, plant-based egg white analogs were successfully produced using 10 w% RuBisCO solutions (pH 8). These protein solutions had similar apparent viscosity-shear rate profiles, shear modulus-temperature profiles, gelling temperatures, and final gel strengths as egg white. However, there were some differences. RuBisCO protein gels were slightly darker than egg white, which was attributed to the presence of phenolic impurities. Moreover, RuBisCo proteins exhibited a single thermal transition temperature (∼66 °C) whereas egg white proteins exhibited two (∼66 and ∼81 °C). RuBisCO gels were more brittle but less chewy and resilient than egg white gels. This study provides valuable insights into the potential of RuBisCO protein for formulating plant-based egg white analogs.

Recent Advances in the Gastrointestinal Fate of Organic and Inorganic Nanoparticles in Foods.

Inorganic or organic nanoparticles are often incorporated into foods to enhance their quality, stability, nutrition, or safety. When they pass through the gastrointestinal environment, the properties of these nanoparticles are altered, which impacts their biological effects and potential toxicity. Consequently, there is a need to understand how different kinds of nanoparticles behave within the gastrointestinal tract. In this article, the current understanding of the gastrointestinal fate of nanoparticles in foods is reviewed. Initially, the fundamental physicochemical and structural properties of nanoparticles are discussed, including their compositions, sizes, shapes, and surface chemistries. Then, the impact of food matrix effects and gastrointestinal environments on the fate of ingested nanoparticles is discussed. In particular, the influence of nanoparticle properties on food digestion and nutraceutical bioavailability is highlighted. Finally, future research directions are highlighted that will enable the successful utilization of nanotechnology in foods while also ensuring they are safe.

Lutein-Fortified Plant-Based Egg Analogs Designed to Improve Eye Health: Formation, Characterization, In Vitro Digestion, and Bioaccessibility.

Lutein is a carotenoid found in real eggs that has been reported to have beneficial effects on eye health by reducing the risk of age-related macular degeneration. However, lutein is not often included in plant based (PB) egg analogs. It would, therefore, be advantageous to fortify PB eggs with this health-promoting carotenoid. Moreover, lutein is a natural pigment with a bright red to yellowish color depending on its concentration and environment. It can, therefore, also be used as a plant-based pigment to mimic the desirable appearance of egg yolk. Some of the main challenges to using lutein as a nutraceutical and pigment in PB foods are its poor water-solubility, chemical stability, and bioavailability. In this study, we encapsulated lutein in oil-in-water emulsions, which were then utilized to formulate whole egg analogs. Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) protein isolated from a sustainable plant-based source (duckweed) was used to mimic the thermally irreversible heat-set gelling properties of globular egg proteins, with the aim of obtaining a similar cookability and texture as real eggs. The lutein content (80 mg/100 g) of the egg analogs was designed to be at a level where there should be health benefits. The protein (12.5 wt.%) and oil (10 wt.%) contents of the egg analogs were selected to match those of real egg. The effects of oil droplet size and oil type on the bioaccessibility of the encapsulated lutein were examined using the INFOGEST in vitro digestion model. For the emulsions formulated with long chain triglycerides (LCTs, corn oil), lutein bioaccessibility significantly increased when the initial droplet diameter decreased from around 10 to 0.3 µm, which was attributed to more rapid and complete digestion of the lipid phase for smaller droplets. For medium chain triglycerides (MCTs), however, no impact of droplet size on lutein bioaccessibility was observed. A high lutein bioaccessibility (around 80%) could be obtained for both LCTs and MCTs emulsions containing small oil droplets. Thus, both types of oil can be good carriers for lutein. In summary, we have shown that lutein-fortified PB eggs with good digestibility and bioaccessibility can be created, which may play an important role in ensuring the health of those adopting a more plant-based diet.

Comparison of Lutein Bioaccessibility from Dietary Supplement-Excipient Nanoemulsions and Nanoemulsion-Based Delivery Systems.

The impact of lutein-loaded nanoemulsions and excipient nanoemulsions mixed with lutein-based dietary supplements (capsules and soft gels) on the bioaccessibility of lutein was explored using a simulated gastrointestinal tract (GIT). The particle size, particle size distribution, ζ-potential, microstructure, lipid digestibility, and lutein bioaccessibility of all the samples were measured after they were exposed to different environments (stomach and small intestine environments) within a simulated GIT. As expected, the bioaccessibility of lutein from the capsules (1.5%) and soft gels (3.2%) was relatively low when they were administered alone. However, the co-administration of excipient nanoemulsions significantly increased the bioaccessibility of lutein from both the capsules (35.2%) and soft gels (28.7%). This phenomenon was attributed to the fast digestion of the small oil droplets in the excipient nanoemulsions and the further formation of mixed micelles to solubilize any lutein molecules released from the supplements. The lutein-loaded nanoemulsions exhibited a much higher lutein bioaccessibility (86.8%) than any of the supplements, which was attributed to the rapid release and solubilization of lutein when the lipid droplets were rapidly and extensively digested within the small intestine. This study indicates that the bioaccessibility of lutein is much higher in nanoemulsion droplets than that in dietary supplements. However, consuming dietary supplements in the presence of nanoemulsion droplets can greatly increase lutein bioavailability. The results of this study have important guiding significance for the design of more effective lutein supplements.

Digestibility and gastrointestinal fate of meat versus plant-based meat analogs: An in vitro comparison.

Plant-based meat analogs are likely to have different gastrointestinal fates than real meat products due to differences in their compositions and structures. Here, we compared the gastrointestinal fate of ground beef and ground beef analogs using the INFOGEST in vitro digestion model, focusing on differences in microstructure, physicochemical properties, lipid digestion, and protein digestion in different regions of the model gut. The presence of dietary fibers in the beef analogs increased their apparent shear viscosity in the gastrointestinal fluids, which may have inhibited lipid digestion in the small intestine. The proteins in the beef analogs were digested more rapidly in the stomach but less rapidly in the small intestine, which may have been due to differences in protein type (globular soy versus fibrous beef proteins), structural organization, and the presence of dietary fibers in the meat analogs.

Bioaccessibility of oil-soluble vitamins (A, D, E) in plant-based emulsions: impact of oil droplet size.

We systematically investigated the impact of oil droplet diameter (≈0.15, 1.6, and 11 µm) on the bioaccessibility of three oil-soluble vitamins (vitamin A palmitate, vitamin D, and vitamin E acetate) encapsulated within soybean oil-in-water emulsions stabilized by quillaja saponin. Lipid digestion kinetics decreased with increasing droplet size due to the reduction in oil-water interfacial area. Vitamin bioaccessibility decreased with increasing droplet size from 0.15 to 11 µm: 87 to 39% for vitamin A; 76 to 44% for vitamin D; 77 to 21% for vitamin E. Vitamin bioaccessibility also decreased as their hydrophobicity and molecular weight increased, probably because their tendency to remain inside the oil droplets and/or be poorly solubilized by the mixed micelles increased. Hydrolysis of the esterified vitamins also occurred under gastrointestinal conditions: vitamin A palmitate (∼90%) and vitamin E acetate (∼3%). Consequently, the composition and structure of emulsion-based delivery systems should be carefully designed when creating vitamin-fortified functional food products.

Encapsulation of lipophilic polyphenols in plant-based nanoemulsions: impact of carrier oil on lipid digestion and curcumin, resveratrol and quercetin bioaccessibility.

Lipophilic polyphenol compounds (LPCs) are claimed to exhibit a broad spectrum of biological activities that may improve human health and wellbeing, including antioxidant, anti-inflammatory, and anti-cancer properties. Nanoemulsion-based delivery systems have been developed to encapsulate LPCs so as to increase their food matrix compatibility, physicochemical stability, and bioavailability. LPCs vary in their structural features, including the number and position of phenolic hydroxyl, ketone, and aliphatic groups, which results in different molecular, physicochemical, and gastrointestinal properties. In this study, we examined the impact of plant-based carrier oils (coconut, sunflower, and flaxseed oils) and LPC type (curcumin, resveratrol, and quercetin) on the in vitro gastrointestinal fate of polyphenols loaded into quillaja saponin-stabilized nanoemulsions. Coconut oil contains high levels of medium-chain saturated fatty acids (MC-SFAs), sunflower oil contains high levels of long-chain monounsaturated fatty acids (LC-MUFAs), and flaxseed oil contains high levels of long-chain polyunsaturated fatty acids (LC-PUFAs). The encapsulation efficiency and gastrointestinal stability of the LPCs were slightly lower in the MC than the LC oils. Differences in the gastrointestinal stability of the three LPCs were linked to differences in their oil-water partition coefficients. Some of the LPCs inhibited lipid digestion for certain oil types. In particular, resveratrol retarded the digestion of all three oils, but it still had the highest GIT stability and bioaccessibility. This study provides valuable information about the gastrointestinal fate of LPC-loaded nanoemulsions and highlights important differences in the behavior of LPCs with different characteristics. This knowledge may facilitate the design of more effective plant-based delivery systems for bioactive lipophilic polyphenols.

Enhancing emulsion functionality using multilayer technology: Coating lipid droplets with saponin-polypeptide-polysaccharide layers by electrostatic deposition.

Electrically charged food-grade biopolymers can be used to form multilayer coatings around the lipid droplets in oil-in-water emulsions using a sequential layer-by-layer electrostatic deposition approach. In principle, this approach can be used to improve the stability and enhance the functionality of food emulsions. In this study, multilayer coatings were formed from saponins, polypeptides, and polysaccharides using medium chain triglyceride (MCT) lipid droplets as templates (pH 4.0). First, an emulsion containing negatively charged lipid droplets was created using quillaja saponin (QS) as an anionic emulsifier. Second, these anionic droplets were coated with a cationic polypeptide (poly-L-lysine, PLL) to form positively-charged droplets. Finally, these cationic droplets were coated with a negatively-charged polysaccharide, either pectin (PE) or κ-carrageenan (KC), to form anionic droplets. Overall, the 1-layer emulsions had the best resistance to salt, pH, and heat, indicating that quillaja saponins were effective emulsifiers. The 2-layer emulsions had better pH-stability than the 3-layer emulsions, which tended to strongly aggregate under acidic conditions. Conversely, the 3-layer emulsions had better salt-stability than the 2-layer emulsions, which tended to aggregate strongly even at low salt levels (50-100 mM NaCl). All the emulsions were relatively stable to heating (90 °C, 30 min). Overall, our results provide useful insights into the formulation of stable multilayer emulsions from food-grade emulsifiers and biopolymers. There appears to be little advantage to using the multilayer technology to enhance the physical stability of saponin-coated lipid droplets, but there may be advantages in terms of extending their functional properties, which will be explored in future studies.

Fortification of Plant-Based Milk with Calcium May Reduce Vitamin D Bioaccessibility: An In Vitro Digestion Study.

Many plant-based milks lack key micronutrients found in bovine milk, such as calcium and vitamin D. In this study, we fortified almond milk with these two micronutrients and used a standardized gastrointestinal model to examine the impact of product formulation on their bioaccessibility. The impact of different forms (CaCl2 versus CaCO3) and concentrations (0, 1, or 2 g per 240 mL) of calcium on the physicochemical properties, lipid digestibility, and vitamin D bioaccessibility was examined. Soluble calcium (CaCl2) promoted particle aggregation by reducing the electrostatic repulsion, while colloidal calcium (CaCO3) did not because there were fewer free calcium ions. High levels of calcium (soluble or insoluble) reduced vitamin D bioaccessibility, which was attributed to insoluble calcium soap formation in the small intestine. Calcium bioaccessibility was higher for CaCO3 than CaCl2. These findings are useful for the development of nutritionally fortified plant-based milks with improved physicochemical and nutritional properties.

In Vitro Gastrointestinal Stability of Lipophilic Polyphenols is Dependent on their Oil-Water Partitioning in Emulsions: Studies on Curcumin, Resveratrol, and Quercetin.

Many lipophilic polyphenols have low bioavailability because of their poor solubility and chemical stability within the human gut. The encapsulation of these polyphenols within digestible lipid droplets can improve their solubility and stability. However, there is currently a poor understanding of how the molecular and physicochemical properties of specific polyphenols impact these characteristics. In this study, the factors influencing the solubility and stability of different polyphenols (curcumin, resveratrol, and quercetin) under simulated gastrointestinal conditions were examined when they were delivered in the form of soybean oil-in-water nanoemulsions containing quillaja saponin-coated droplets (d32 ≈ 0.15 µm; ζ = -63 mV; pH 5). The polyphenols were loaded into the lipid droplets using a pH-driven method, which is based on the pH-dependent electrical charge, oil-water partitioning, and water-solubility of these molecules. The encapsulation efficiency of all three polyphenols was relatively high (75-87%). However, their chemical stability under gastrointestinal conditions (i.e., the % remaining after exposure to gastrointestinal conditions) differed considerably: quercetin (44%), curcumin (92%), and resveratrol (100%). This effect was mainly attributed to the lower logD value of quercetin (2.17) than those of resveratrol (3.39) and curcumin (4.12). As a result, a high fraction (>50%) of quercetin was located within the aqueous gastrointestinal fluids, where it would be more prone to chemical degradation or precipitation. The fraction of the polyphenols solubilized in the gastrointestinal fluids (bioaccessibility) followed a different trend: curcumin (57%) < quercetin (73%) < resveratrol (76%). This effect was attributed to the chemical instability and/or binding of curcumin with other molecules in the simulated intestinal conditions. These results provide useful information for designing nanoemulsion-based delivery systems to improve the efficacy of lipophilic polyphenols.

Stabilization of soybean oil-in-water emulsions using polypeptide multilayers: Cationic polylysine and anionic polyglutamic acid.

Oil-in-water emulsions are used as delivery systems for non-polar functional ingredients in various industries, including foods, cosmetics, personal care products, agrochemicals, and pharmaceuticals. Emulsions, however, tend to breakdown under the conditions found in many commercial products. In this study, the functional performance of the lipid droplets in emulsions was tailored by sequential layer-by-layer electrostatic deposition of oppositely charged polypeptides onto their surfaces. Cationic poly-L-lysine (PLL) and anionic poly-glutamic acid (PGA) were used as a pair of oppositely charged polypeptides (pH 4.0). First, a primary emulsion (10% w/w soybean oil-in-water emulsion) was formed consisting of small lipid droplets (d32 = 500 µm) coated by a natural surfactant (0.05% w/w quillaja saponin). Second, cationic PLL was deposited onto the surfaces of the anionic saponin-coated droplets. Third, anionic PGA was deposited onto the surfaces of the cationic PLL-saponin-coated droplets. We then assessed the ability of the coatings to protect the lipid droplets from aggregation when the pH (2.0-9.0), ionic strength (0-350 mM), or temperature (30-90 °C) were altered. The properties of the primary, secondary, and tertiary emulsions were monitored by measuring the mean particle diameter (d32), electrical characteristics (ζ-potential), and microstructure of the lipid droplets. The electrical characteristics of the droplets could be modulated by controlling the number and type of layers used. The primary emulsion had the best resistance to varying environmental conditions, while the secondary emulsion had the worst, suggesting electrostatic deposition should only be used to obtain specific functionalities. Interestingly, PLL detached from the surfaces of the secondary emulsions at high salt concentrations due to electrostatic screening, which improved their salt stability. This phenomenon may be useful for some food applications, e.g., having cationic droplets during food storage, but anionic ones inside the human body.

Factors impacting lipid digestion and ß-carotene bioaccessibility assessed by standardized gastrointestinal model (INFOGEST): oil droplet concentration.

Food, nutrition, and pharmaceutical scientists are trying to elucidate the major factors impacting the bioavailability of macronutrients (e.g., lipids) and micronutrients (e.g., vitamins) so as to improve their efficacy. Currently, there is still a limited understanding of how food matrix effects impact digestion and bioaccessibility determined under the INFOGEST model, which is currently the most widely used standardized in vitro gastrointestinal model. Therefore, we examined the impact of corn oil concentration on lipid digestion and ß-carotene bioaccessibility using model food emulsions. For all oil concentrations tested (2.5 to 20%), complete lipid digestion was achieved using fed-state gastrointestinal conditions, which could only be seen if a back-titration was performed. The particle size and negative surface potential on the mixed micelles formed at the end of the small intestine phase both increased with increasing oil concentration, which was attributed to the generation of more free fatty acids. The ß-carotene bioaccessibility increased when the oil concentration was raised from 2.5 to 10% due to the increased solubilization capacity of the mixed micelles, but then it decreased when the oil concentration was raised further to 20% due to precipitation and sedimentation of some of the ß-carotene. The maximum ß-carotene bioaccessibility (93.2%) was measured at 10% oil. These results indicate that the oil concentration of emulsions influences ß-carotene bioaccessibility by altering digestion, solubilization, and precipitation processes. This knowledge is important when designing more effective functional or medical food products.

Impact of fat crystallization on the resistance of W/O/W emulsions to osmotic stress: Potential for temperature-triggered release.

Water-in-oil-in-water (W/O/W) emulsions can be designed to encapsulate, protect, and release both hydrophilic and hydrophobic functional compounds. In this study, we examined the impact of crystallizing the fat phase on the resistance of W/O/W emulsions to osmotic stress, with the aim of developing osmotic-responsive systems. Polyglycerol polyricinoleate (PGPR) was used as a hydrophobic surfactant to stabilize the inner water droplets, while Quillaja saponin and whey protein isolate (WPI) were used as hydrophilic surfactants to coat the oil droplets. The impact of fat crystallization was examined by using either a liquid (soybean oil, SO) or semi-solid (hydrogenated soybean oil, HSO) fat as the oil phase. An osmotic stress was generated by establishing a sucrose concentration gradient between the internal and external water phases. Alterations in the droplet size, morphology, and stability of the W/O/W emulsions was measured when the sucrose concentration gradient was changed. The W/O droplets in the SO-emulsions swelled/shrank when the external sucrose concentration was below/above the internal sucrose concentration, which is indicative of water diffusing into/out of the droplets. Conversely, there was no change in the size of the W/O droplets in the HSO-emulsions under the same conditions, which was attributed to the mechanical strength of the fat crystal network resisting swelling or shrinking. HSO-emulsions did exhibit swelling when they were heated above a critical temperature, due to melting of the fat crystals and disruption of the crystal network. Our results demonstrate that crystallization of the oil phase of W/O/W emulsions can prevent water transport due to osmotic stress, which may be useful for developing temperature-triggered delivery systems for application in foods, cosmetics, pharmaceuticals, or personal care products.