Nutraceutical Bioaccessibility Research Articles

Ovalbumin fibril-stabilized oleogel-based Pickering emulsions improve astaxanthin bioaccessibility

The present study aimed to enhance the bioaccessibility of hydrophobic astaxanthin (AST) by developing food-grade emulsion systems. Ovalbumin (OVA) fibrils and candelilla wax-based oleogels were prepared for the next fabrication of AST-loaded oleogel-based Pickering emulsions. The food-grade oleogel was obtained by mixing 0.7% (w/w) candelilla wax and soybean oil. The nano-scale OVA fibrils were observed by transmission electron microscope. SDS-PAGE analysis of OVA fibrils displayed the appearance of peptides with molecular weight around 10 kDa. Contact angle measurement indicated that excellent amphiphilicity endowed OVA fibrils with satisfactory Pickering emulsifier performance. The obtained oleogel-based Pickering emulsions displayed ultrastability during 90-day storage and outstanding freeze-thaw stability. Furthermore, the superiority of AST-loaded oleogel-based Pickering emulsion was further reflected in the apparently ameliorative lipolysis extent and AST bioaccessibility compared with oleogel. This work would facilitate the utilization of OVA and the development of oleogel-based Pickering emulsions with desirable nutraceutical bioaccessibility.

Fabrication and characterization of core-shell gliadin/tremella polysaccharide nanoparticles for curcumin delivery: Encapsulation efficiency, physicochemical stability and bioaccessibility

The objectives of the present study were to synthesize gliadin/tremella polysaccharide nanoparticles (Gli/TP NPs) as well as curcumin-loaded gliadin/tremella polysaccharide nanoparticles (Cur-Gli/TP NPs) and evaluate the encapsulation efficiency (EE), physicochemical stability and bioaccessibility of Cur-Gli/TP NPs. The physicochemical properties of the nanoparticles depended on the mass ratio of Gli to TP and pH values. The characterization of the Gli/TP NPs indicated that the prepared nanoparticles were the most stable when the Gli/TP mass ratio was 1:1 and pH was at 4.0–7.0. Afterward, prepared Cur-Gli/TP NPs at different pH values were studied. Compared with the EE of Cur (58.2%) in Cur-Gli NPs at pH 5.0, the EE of Cur (90.6%) in Cur-Gli/TP NPs at pH 5.0 was increased by 32.4%. Besides, the Cur-Gli/TP NPs possessed excellent physical stability, photostability, thermal stability and re-dispersibility than Cur-Gli NPs. Furthermore, the bioaccessibility of Cur reached 83.5% after encapsulation of Cur into Gli/TP NPs after in vitro digestion, indicating that Cur-Gli/TP NPs could improve curcumin bioaccessibility significantly. In summary, this study demonstrates that the new food-grade Gli/TP NPs possess high encapsulation efficiency, excellent stability and prominent nutraceutical bioaccessibility. Meanwhile, it contributes to expanding the application of TP in food-grade delivery systems.

Impact of composite gelators on physicochemical properties of oleogels and astaxanthin delivery of oleogel-based nanoemulsions

In this study, binary systems of carnauba wax (CW) and 1-docosanol (DS) were first explored to enhance the properties of oleogels. Compared to the corresponding single component oleogels (0:5 and 5:0), a synergistic effect of oleogel strength was observed at CW:DS ratios of 1:4 (C1D4). At this ratio, the formed oleogel showed the highest hardness, rheological property and oil binding ability. Meanwhile, the gel-sol melting temperature of this oleogel at this ratio was lower than most of others. Subsequently, the effect of composite gelators on the astaxanthin delivery of oleogel-based nanoemulsion was explored. The oleogels at CW:DS ratios of 1:4, 0:5 and 5:0 were chosen to prepare oleogel-based nanoemulsions. The oleogel-based nanoemulsion formulated with C1D4 had the largest droplet size. In vitro digestion study revealed that although C1D4 oleogel-based nanoemulsion could not improve the extent of lipolysis, it could significantly improve astaxanthin bioaccessibility when compared with the other two oleogel-based nanoemulsions. This study developed a new formula of oleogel-based nanoemulsion with improved astaxanthin bioaccessibility. This novel formulation approach might also be suitable for other hydrophobic nutraceuticals and provided a new idea for the preparation of oleogel-based nanoemulsions with improved nutraceutical bioaccessibility.

Factors impacting lipid digestion and nutraceutical bioaccessibility assessed by standardized gastrointestinal model (INFOGEST): Emulsifier type

This paper is part of a series examining the impact of the main factors influencing lipid digestion and nutraceutical bioaccessibility in β-carotene-loaded oil-in-water emulsions using the harmonized INFOGEST simulated gastrointestinal model. Here, the impact of emulsifier type was examined since food emulsions and nutraceutical delivery systems are often stabilized by various types of emulsifier. The INFOGEST method was adopted to investigate the in vitro gastrointestinal fate of emulsions stabilized by five kinds of food-grade emulsifier representing different classes: synthetic surfactants (Tween 20); natural surfactants (quillaja saponin); proteins (caseinate); polysaccharides (gum arabic); and phospholipids (soy lysolecithin). Microfluidization produced emulsions with small droplet sizes for all emulsifiers, except soy lysolecithin. Within the gastrointestinal model, the caseinate-coated oil droplets had the worst gastric stability, with severe droplet flocculation and coalescence occurring in the stomach. The fraction of the lipid phase that had been digested by the end of the gastrointestinal model was considerably lower for the emulsions stabilized by soy lysolecithin (93%) or caseinate (93%), than those stabilized by gum arabic (99%), quillaja saponin (111%) or Tween 20 (117%). This effect was attributed to lower surface area of lipids available for lipase to attach to for the lysolecithin and caseinate emulsions. The overall bioaccessibility of the β-carotene increased in this order: lysolecithin (25%) < gum arabic (51%) < caseinate (55%) < quillaja saponin (56%) < Tween 20 (62%). The impact of emulsifier type on carotenoid bioaccessibility was ascribed to various factors: (i) some emulsifiers inhibited lipid digestion and so a fraction of the β-carotene remained inside the undigested droplets and the mixed micelle phase had less solubilization capacity, i.e., lysolecithin, and caseinate; (ii) some emulsifiers protected β-carotene from chemical degradation, i.e., lysolecithin and caseinate; and (iii) some emulsifiers promoted sedimentation of the β-carotene-loaded micelles, i.e., lysolecithin. These results suggest that food emulsion behavior in the human gut may be influenced by the nature of the emulsifier employed, which is important knowledge when creating functional food and beverage products.

In vitro digestion studies of the impact of food matrix effects on vitamin and nutraceutical bioaccessibility

In vitro digestion studies of the impact of food matrix effects on vitamin and nutraceutical bioaccessibility

Impact of calcium levels on lipid digestion and nutraceutical bioaccessibility in nanoemulsion delivery systems studied using standardized INFOGEST digestion protocol

Recently, the standardized in vitro digestion model ("INFOGEST method") used to evaluate the gastrointestinal fate of foods has been revised and updated (Brodkorb et al., 2019, Nat. Protoc., 2019, 14, 991-1014). Under fed state conditions, the calcium level used in this model is fixed and relatively low: 0.525 mM. In practice, the calcium concentration in the human gut depends on the nature of the food consumed and may vary from person-to-person. For this reason, we examined the impact of calcium concentration on the gastrointestinal fate of a model nutraceutical delivery system. The effect of calcium level (0.525-10 mM) on lipid digestion and β-carotene bioaccessibility in corn oil-in-water nanoemulsion was investigated using the INFOGEST method. At all calcium levels, the lipids were fully digested, but this could only be established by carrying out a back titration (to pH 9) at the end of the small intestine phase. Conversely, the bioaccessibility of β-carotene decreased with increasing calcium levels: from 65.5% at 0.525 mM Ca2+ to 23.7% at 10 mM Ca2+. This effect was attributed to the ability of the calcium ions to precipitate the β-carotene-loaded mixed micelles by forming insoluble calcium soaps. The ability of calcium ions to reduce carotenoid bioaccessibility may have important nutritional implications. Our results show that the bioaccessibility of hydrophobic carotenoids measured using the INFOGEST method is highly dependent on the calcium levels employed, which may have important consequences for certain calcium-rich foods. Moreover, we have shown the importance of carrying out a back titration to accurately measure free fatty acid levels in the presence of low calcium levels.

Factors impacting lipid digestion and nutraceutical bioaccessibility assessed by standardized gastrointestinal model (INFOGEST): oil.

The oil droplets in commercial emulsified foods have dimensions that vary widely, from hundreds of nanometers to tens of micrometers. Previously, the size of the droplets in oil-in-water emulsions has been shown to impact their gastrointestinal behavior, which may influence their physiological effects. In this study, we analyzed the impact of oil droplet diameter (0.16, 1.1 and 8.2 μm) on lipid digestion and nutraceutical bioaccessibility using a widely used standardized gastrointestinal tract model: the INFOGEST method. The emulsions used consisted of corn oil droplets stabilized using a food-grade non-ionic surfactant (Tween 20), and the droplet size was controlled by preparing them with a microfluidizer (small), sonicator (medium), or high-shear blender (large). The surfactant-coated oil droplets were relatively resistant to size changes in the mouth and stomach, due to the strong surface activity and steric stabilization mechanism of the non-ionic surfactant used. As expected, the kinetics of lipid digestion were enhanced for smaller droplets because of their greater specific surface area. The degree of lipid digestion fell from 117% to 78% (p < 0.001) as the initial droplet diameter was raised from 0.16 to 8.2 μm. In addition, there was a reduction in β-carotene bioaccessibility from 83 to 15% (p < 0.001) with increasing droplet diameter. This result was ascribed to several effects: (i) some carotenoids were trapped inside the undigested oil phase; (ii) fewer mixed micelles were produced to internalize the carotenoids; and, (iii) a fraction of the carotenoids crystallized and sedimented. Our results underline the critical importance of considering droplet size when developing emulsified foods loaded with carotenoids. The results obtained by the INFOGEST method are consistent with those found using other in vitro methods in earlier studies.

Ovotransferrin fibril-stabilized Pickering emulsions improve protection and bioaccessibility of curcumin.

The present study aimed to investigate protection and bioaccessibility of curcumin in ovotransferrin (OVT) fibril-stabilized Pickering emulsions. Curcumin protection of OVT fibril-stabilized emulsions against ultraviolet light exposure was studied. OVT fibril-stabilized Pickering emulsion at an ionic strength of 1000 mM provided the best curcumin protection. OVT fibril-stabilized Pickering emulsion at pH 6 provided better curcumin protection than those at pH 2 and 4. Afterwards, digestion of OVT fibril-stabilized curcumin emulsion was investigated in both TNO dynamic digestion model (TIM-1) and pH-stat static digestion model. In terms of TIM-1 result, curcumin bioaccessibility in OVT fibril-stabilized emulsion increased by 129% when compared with that in bulk oil. In pH-stat digestion model, curcumin bioaccessibility increased by 114% after formulated into OVT fibril-stabilized droplets, which was due to higher extent of lipolysis. Interestingly, both TIM-1 and pH-stat digestion models gave almost consistent measurements of improved percentage in curcumin bioaccessibility. Curcumin bioaccessibility of the emulsion in TIM-1 and pH-stat model was 15.3% and 33.8% respectively, indicating bioaccessibility overestimation in pH-stat model. The novel findings in this work could facilitate designing food-grade Pickerinng emulsion with excellent nutraceutical protection and enhanced nutraceutical bioaccessibility.

Developing organogel-based Pickering emulsions with improved freeze-thaw stability and hesperidin bioaccessibility

Soybean oil-based organogel was structured using monostearin, and the organogel had a gel-sol melting temperature of 44.0 °C. Loading amount of hesperidin in soybean oil-based organogels could be about twice as much as metastable solubility of hesperidin in soybean oil. Organogel-in-water Pickering emulsion was formed using the soybean oil-based organogel as the oil phase and ovotransferrin (OVT) fibrils as the emulsifier. Visual observation indicated that organogel-based Pickering emulsions stabilized by OVT fibrils (40 mg/mL) at oil fractions of 0.50–0.85 had excellent storage stability and could withstand three cycles of freeze-thaw treatments. Conventional oil-in-water Pickering emulsion was prepared as control to better understand impact of organogel incorporation on freeze-thaw stability, and conventional Pickering emulsion was formed using soybean oil as the oil phase and OVT fibrils as the emulsifier. Freeze-thaw stability of organogel-based Pickering emulsions was better than that of conventional Pickering emulsions (without organogel) stabilized by OVT fibrils. In vitro digestion study revealed that organogel-based Pickering emulsion could improve both the extent of lipolysis and hesperidin bioaccessibility when compared with organogel. This study demonstrates the feasibility of formulating novel food-grade organogel-based Pickering emulsions with high nutraceutical loading, excellent freeze-thaw stability and improved nutraceutical bioaccessibility.

Enhancement of the solubility, stability and bioaccessibility of quercetin using protein-based excipient emulsions

Emulsion-based excipient foods were developed to improve the bioaccessibility of an important hydrophobic nutraceutical: quercetin. Protein-stabilized oil-in-water excipient emulsions were prepared using sodium caseinate, whey protein isolate, or soy protein isolate as an emulsifier. These emulsions were then mixed with powdered quercetin and heated to simulate a cooking process. The excipient emulsions had relatively small droplet sizes (d < 270 nm) and remained stable against coalescence after exposure to boiling (100 °C for 60 min). In particular, casein was shown to be better at adsorbing to oil-water interface and contributed to a more stable interfacial layer than the other two proteins. Quercetin was solubilized in the emulsions during heating, which may be attributed to dissolution in the oil phase and complexation with proteins. There were appreciable differences in quercetin bioaccessibility in excipient emulsions stabilized by different emulsifiers (≈74% for casein, 54% for whey protein, 22% for soy protein, and 58% for Tween). This study suggests that milk proteins may be natural alternatives to synthetic surfactants for forming stable excipient emulsions capable of enhancing nutraceutical bioaccessibility.

Control of lipid digestion and nutraceutical bioaccessibility using starch-based filled hydrogels: Influence of starch and surfactant type

The aim of this study was to prepare starch-based filled hydrogels fortified with a model lipophilic nutraceutical (β-carotene) and determine the influence of starch type (mung bean or rice starch) and surfactant type (whey protein isolate (WPI) or Tween 20 (T20)) on lipid digestibility and β-carotene bioaccessibility. Microstructure, lipid digestion, and β-carotene bioaccessibility were measured as the emulsions and filled hydrogels were passed through a simulated gastrointestinal tract that included oral, gastric, and intestinal phases. The bioaccessibility was defined as the fraction of β-carotene solubilized within the mixed micelle phase after lipid digestion. Non-encapsulated T20-stabilized emulsions had better aggregation stability than WPI-stabilized emulsions under simulated gastrointestinal conditions, which led to a higher β-carotene bioaccessibility. Both Tween 20- and WPI-stabilized emulsions incorporated in starch-based filled hydrogels led to high lipid digestion and β-carotene bioaccessibility. The release behavior of free fatty acids during lipase digestion depended on the type of starch used as a hydrogel matrix, which was attributed to differences in starch structure. The information obtained in this study may be useful for the fortification of starch-based gelled products with lipophilic nutraceuticals.