Stability Of Α-tocopherol Research Articles

Improving the Stability, Water Solubility, and Antioxidant Activity of α-Tocopherol by Encapsulating It into Niosomes Modified with Cationic Carbamate-Containing Surfactants.

The low solubility of α-tocopherol in water and its susceptibility to photodegradation make it difficult for biological systems to absorb this natural antioxidant. To overcome these limitations, α-tocopherol was encapsulated in low-toxicity nanocontainers, namely, niosomes based on Tween 80 and cholesterol. The niosomes were modified with cationic surfactants containing a carbamate fragment. The size and charge of the particles were determined and their stability was assessed using dynamic and electrophoretic light scattering methods. It was found that the introduction of cationic surfactants to niosome formulations significantly improved their physicochemical properties and increased stability due to a positive charge of up to +40 mV being generated. Modified niosomes loaded with α-tocopherol were characterized by a hydrodynamic diameter of 100-120 nm, a narrow particle size distribution, and a high encapsulation efficiency of more than 90%. Testing the photochemical stability of α-tocopherol using a spectrophotometric method demonstrated that niosomes were able to protect this substance from UV irradiation. Luminescence analysis showed that the inclusion of α-tocopherol in niosomes increased their antioxidant activity by 30%. An acute toxicity study has demonstrated the safety of the systems. The LD50 value for niosomes modified with carbamate-containing surfactants and loaded with α-tocopherol exceeded 10,000 mg·kg-1 (mice, intraperitoneal and oral administration).

Emulsions vs excipient emulsions as α-tocopherol delivery systems: Formulation optimization and behaviour under in vitro digestion

Oil-in-water emulsions (EM) have been extensively used for the encapsulation of lipophilic bioactive compounds and posterior incorporation into food matrices to obtain functional foods. Conversely, novel excipient oil-in-water emulsions (EXC) present identical composition and structure as EM, albeit are not bioactive by themselves since no bioactive compound is encapsulated. Instead, EXC aims at improving the bioavailability of foods’ natural bioactive compounds upon co-ingestion with nutrient-rich foods. In this work, EM and EXC were produced and their stability and functionality as delivery systems for α-tocopherol compared. Emulsions were formulated with corn oil and lecithin, and their composition was optimized using experimental designs. Formulations produced with 3 % lecithin and 5 % oil attained smallest particles sizes with the lowest polydispersity index of all tested formulations and remained stable up to 60 days. Encapsulation of α-tocopherol did not have a significative impact on the structural properties of the particles produced with the same composition. α-tocopherol stability during in vitro digestion was superior in EM regardless the processing methodology (EM stability < 50 %, EXC stability < 29 %), indicating that EM offered greater protection against the digestive environment. α-tocopherol’s bioaccessibility was significantly increased when encapsulated or when digested with added excipient emulsions (82–92 % and 87–90 % for EM and EXC, respectively). In conclusion, EM were more efficient vehicles for the selected bioactive compound, however, the good results obtained with EXC imply that excipient emulsions have a great potential for applications on foods to improve their natural bioactive compounds’ bioavailability without the need of further processing.

“Characterization and stability of α-tocopherol loaded solid lipid nanoparticles formulated with different fully hydrogenated vegetable oils”

Solid lipid nanoparticles can be compatible with several bioactive compounds and confer a differentiated crystalline structure. This study aimed to produce α-tocopherol loaded solid lipid nanoparticles with fully hydrogenated oils and fats from palm oil, soybean oil, and crambe oil, by high-pressure homogenization, using lecithin as an emulsifier. After recrystallization of solid lipid nanoparticles, dispersions were evaluated until 60 days of storage for particle size, polydispersity index, zeta potential, microstructure, dispersion stability and α-tocopherol quantification. α-tocopherol loaded solid lipid nanoparticles showed particle sizes and zeta potential values considered adequate for this type of particle. Presence of α-tocopherol altered thermal behavior of the particles, leading to increased crystallinity, with no changes in polymorphism, when compared to the unloaded solid lipid nanoparticles. All α-tocopherol loaded solid lipid nanoparticles dispersions showed stability with no losses of α-tocopherol, indicating their potential as a carrier for this compound in fortified foods.

Evaluation of α-tocopherol microencapsulation stability with either coconut oil or canola oil cores in Greek yogurt and butter

Worldwide vitamin-E consumption is below the recommended daily allowance (RDA). Therefore, the present work developed functional yogurt/butter with α-tocopherol microencapsulated in canola (α-CAN) or coconut oil (α-COC), using ora-pro-nobis mucilage and whey protein isolate as natural wall material. The primary hypothesis is that α-tocopherol degrades faster than its microencapsulated counterpart in whole food systems. Physical characteristics, pH and color remained constant over 28 days. Color varied from the control, with the total color difference (ΔE) ranging from 0.29 (α-free) to 0.87 (α-CAN) for yogurt and 5.07 (α-CAN) to 6.14 (α-free) for butter. The antioxidant activity of yogurt significantly increased from 15.99 (control) to 34.84% (α-COC), and for butter, it increased from 28.94 (control) to 67.03% (α-COC). The α-tocopherol decreased from 16.60 to 12.70 mg/100 g for yogurt and from 15.40 to 12.83 mg/10 g for butter. No significant differences (p>0.05) presented for α-COC, α-CAN, or α-free; hence microencapsulation did not significantly improve α-tocopherol stability. α-tocopherol degradation was greater for yogurt than butter due to the dissolution of the wall material, as both the continuous phase and wall material are hydrophilic, causing the release and oxidation of α-tocopherol. In butter, the fortification was more effective when the core contained coconut oil.

Coating of DNA and DNA complexes on zein particles for the encapsulation and protection of kaempferol and α-tocopherol

Zein particles are potential for the encapsulation of bioactive compounds. Deoxyribonucleic acid (DNA) shows good pH stability and can complex with antioxidants. In this study, DNA and DNA-quercetin complexes was used as the coating layer of zein particles. Zein particles had a size of 85.10 nm and ζ-potential of −30.73 mV at 1 mg/mL DNA. Zein/DNA particles were stable at pH 4–9. Encapsulation efficiency of kaempferol and α-tocopherol in complex particles reached 92.90% and 97.02%, respectively. The potential use of zein/DNA particles was evaluated for protecting kaempferol. Moreover, DNA-quercetin complex coating was investigated to discuss the protection of α-tocopherol in zein particles. The DNA coating improved the storage stability of kaempferol or α-tocopherol by strengthening physical barrier. DNA-quercetin complexes further improved the stability of α-tocopherol by acting as antioxidant barrier. The retention of kaempferol and α-tocopherol was about 58% in zein/DNA and zein/DNA-quercetin particles at 45 °C after 28 days.

Stability and bioaccessibility of α-tocopherol-enriched nanoemulsions containing different edible oils as carriers

Nanoemulsions have been described as carriers of bioactive compounds since they can protect them during digestion and improve their bioaccessibility. However, their stability and bioaccessibility can be influenced by nanoemulsion composition, mainly by the lipid phase characteristics. Consequently, this study aimed to evaluate three different carrier oils (avocado-AVO, flaxseed-FLA, and chia-CHI) on the stability and bioaccessibility of α-tocopherol carried in nanoemulsions. Particle characteristics (particle size-PS and polydispersity index-PdI) and oxidative stability of nanoemulsions, and α-tocopherol degradation during storage were determined. In addition, free fatty acids (FFAs) release kinetics and α-tocopherol bioaccessibility during in vitro digestion were analyzed. Results showed that all nanoemulsions were colloidally stable due to their droplet characteristics (PS < 200 nm and PdI<0.2), where no phase separation was observed. AVO nanoemulsion was the most stable against oxidation due to its high monounsaturated and saturated fatty acids, while CHI nanoemulsion showed the highest chemical stability of α-tocopherol during storage. Besides, AVO nanoemulsion showed the most significant release of FFA (94%) and the highest α-tocopherol bioaccessibility (81%). In conclusion, the oil type affects the chemical stability and bioaccessibility of α-tocopherol carried in nanoemulsions. Thus, AVO oil can be used as a carrier of fat-soluble vitamins to increase its bioaccessibility during digestion.

Degradation kinetic modeling of bioactive compounds and enzyme activity in wheat germ during stabilization

The stability of α-tocopherol (α-toco), total phenolic content (TPC), antioxidant capacity (DPPH and ABTS•+ radical scavenging capacity assays), activity of lipase (LA) and lipoxygenase (LOX) were investigated during stabilization of raw wheat germ with an industrial convection oven at different temperatures (120, 130, 140, 150 and 160 °C) and times (0, 5, 10, 15, and 20 min). Degradation kinetics were best fitted by first-order reaction models for all measured parameters with high R2 and low root mean square (RMSE) values, except ABTSassay which was modeled accurately with the second-order model. The temperature dependence of rate constants for all degradation kinetic parameters were calculated according to the Arrhenius, Eyring-Polanyi, and Ball models. Following the Arrhenius and Eyring models, activation energy (Ea) ranged from 20.69 to 55.04 kJ mol−1, activation enthalpy (ΔH*) ranged from 20.44 to 51.61 kJ mol−1 whereas the activation entropy (ΔS*) varied between −179.313 and −213.447 J mol−1K−1 for the stabilized germ, respectively. It can be concluded that heat treatment at 120 °C for 20 min was the best processing conditions to stabilize the raw germ to preserve its valuable bioactive compounds, antioxidant activity and the models can be useful to design different heat treatment conditions.

Impact of Pleurotus ostreatus β-Glucans on Oxidative Stability of Active Compounds Encapsulated in Powders during Storage and In Vitro Digestion.

Polyunsaturated fatty acids and α-tocopherol were encapsulated in powders by spray drying using maltodextrins DE 12 as wall material and different emulsifiers (Tween®20, acacia gum or β-glucans-rich extracts from Pleurotus ostreatus). The aim was to study the effects of the surfactants on: (a) the oil droplet size distribution and α-tocopherol stability during in vitro digestion, and (b) the oxidative stability during 15 days of accelerated storage. Acacia gum sample had the most stable particle size distribution up to the gastric phase, but showed a significant α-tocopherol degradation prior to the intestinal stage. On the contrary, β-glucan-samples displayed a bimodal distribution in the oral and gastric phases but retained α-tocopherol up to the beginning of the intestinal stage. At the end of intestinal stage, no α-tocopherol was found in the samples. The storage study showed that β-glucans improved the oxidative stability of the powders, which displayed 82% α-tocopherol retention after 5 days under accelerated conditions (60 °C), corresponding to 310 days at 20 °C, while acacia gum and Tween® 20 did not delay α-tocopherol degradation. Results highlight the potential antioxidant activity of β-glucans used as emulsifying agents during in vitro digestion and accelerated aging conditions.

Fabrication and characterisation of whey protein isolate–propolis–alginate complex particles for stabilising α-tocopherol-contained emulsions

Dairy proteins are being used as carrier materials for the co-encapsulation and protection of bioactive nutrients because of their emulsification and complexation with polysaccharides. In this study, whey protein isolate (WPI)-propolis and WPI-propolis-alginate complex particles were fabricated at pH 7.0 and characterised in term of size distribution, ζ-potential, antioxidant activity, and propolis encapsulation. The encapsulation efficiency of propolis was above 80% when 5 mg mL−1 WPI was incorporated. Propolis and α-tocopherol were further co-encapsulated in sunflower oil emulsions stabilised by the complex particles. About 92% α-tocopherol and 72% propolis were co-encapsulated in the inner oil phase and the oil-water interface of emulsions, respectively. Propolis and/or alginate improved the stability of α-tocopherol during storage, while sodium alginate counteracted the positive effect of propolis on the vitamin stability during enzymatic hydrolysis. The data gathered here would expand the use of biopolymer-stabilised emulsions for multi-nutraceutical delivery.

Synthesis of alpha-tocopherol encapsulated chitosan nano-assemblies and their impregnation on cellulosic fabric for potential antibacterial and antioxidant cosmetotextiles

This study describes the encapsulation of alpha (α)-tocopherol in chitosan nanosphere using the emulsion formation method. The α-tocopherol is a versatile antioxidant yet has limited applications due to its feeble stability in oxidizing environments. However, its encapsulation in a suitable capping agent might improve its stability. Chitosan is non-toxic, biodegradable, biocompatible and low-cost biomaterial. It could be used as an encapsulating agent to increase the stability of α-tocopherol and release when required over a sustained period. Once prepared, the encapsulated α-tocopherol nanospheres were characterized using different analytical techniques followed by application on cotton fabric. The treated fabric exhibited slight decrease in absorbency and tensile strength, and good antibacterial activity against broad spectrum bacterial strains. The release of α-tocopherol from the nanospheres in dispersed form was 64% whereas once applied on cotton fabric, the release was observed as 41%; this might be attributed to the cross-linking of nanospheres which decreased the opportunity to release the active ingredient. The produced cosmetotextiles can be used in skin care products particularly to reduce skin dryness with good antibacterial and antioxidant performance.

Partition and digestive stability of α-tocopherol and resveratrol/naringenin in whey protein isolate emulsions

Co-encapsulation of multiple bioactive components is an emerging field that shows promise as an approach to develop functional foods. Hydrophobic components are generally dissolved in the inner oil phase of protein-stabilised emulsions. Some components may co-adsorb to oil droplet surfaces, due to the ligand-binding properties of proteins. In this study, α-tocopherol and resveratrol/naringenin were co-encapsulated in emulsions stabilised by whey protein isolate (WPI). α-Tocopherol was totally encapsulated and its partitioning inside oil droplets was about 3.3 times that bound by free WPI in the aqueous phase. The total encapsulation efficiency for resveratrol or naringenin was 52% and 58%, respectively. Addition of resveratrol improved digestive stability of α-tocopherol, but naringenin did not. Co-encapsulation with α-tocopherol had no significant influence on the digestive stability of resveratrol/naringenin. The data gathered here should be useful for the delivery of bioactive components with different solubilities.

Comparison of whey protein particles and emulsions for the encapsulation and protection of α-tocopherol

Food proteins have been widely used for the preparation of emulsion-based carriers and lipid-free carriers. In this study, whey protein isolate (WPI)-α-tocopherol particles and emulsions were prepared at protein's concentrations from 0.5% to 5.0% and initial concentrations of α-tocopherol ∼0.06% and 0.12%. Concentration of α-tocopherol affected the size of WPI particles but not that of WPI emulsions. ζ-Potential of WPI particles was greater than that of WPI emulsions. Encapsulation efficiency of α-tocopherol was greater in the emulsions than in the particles, but not at 0.12% α-tocopherol and 5.0% WPI. Storage stability of α-tocopherol was better in WPI emulsions than particles at 25 °C and at the intermediate stage of 45 °C but contrary at the ending of storage at 45 °C. The data gathered here should be useful for the development of protein-based carrier systems for hydrophobic components.

Influence of Oxidants on the Stability of Tocopherol in Model Nanoemulsions: Role of Interfacial Membrane Organized by Nonionic Emulsifiers

Nanoemulsions were prepared by using emulsifiers with various sizes of hydrophilic and hydrophobic groups to determine the impact of interfacial characteristics on the stability of α-tocopherol incorporated into the nanoemulsions. The α-tocopherol concentration remaining after 3 weeks of storage at 25°C depended greatly on the type of oxidative stress, which indicated that the environment surrounding the oil droplets could determine the stability of α-tocopherol in nanoemulsions. α-Tocopherol was gradually degraded by radical-mediated oxidation over storage, and approximately 60% of its initial concentration remained after 3 weeks of storage. However, under acid- and iron-mediated oxidation, α-tocopherol concentration steeply decreases for the initial 3-day storage, but the degradation rate of α-tocopherol decreased after 3 days of storage and over 90% of the initial α-tocopherol remained after 3 weeks of storage. Interestingly, and contrary to our expectations, the thickness and/or density of the droplet interfacial membrane rarely affected the stability of α-tocopherol incorporated into nanoemulsions. Although it is difficult to generalize beyond α-tocopherol, we conclude that the properties of oil droplet surfaces had no influence on the storage stability of α-tocopherol encapsulated in the droplets.

Effects of chitosan and collagen containing α-tocopherol on the oxidative stability in bulk oil and oil-in-water emulsion.

To provide efficient antioxidant capacities, proper carriers are needed to protect antioxidants against oxidative stress. Collagen mesh structure or chitosan gel was loaded with α-tocopherol and their effects were evaluated in bulk corn oil or oil-in-water (O/W) emulsion at 60°C. Added collagen and chitosan enhanced oxidative stability in corn oil and O/W emulsions at 60°C compared to corn oils without carriers or with addition of α-tocopherol (p<0.05). Stability of α-tocopherol in corn oil loaded in collagen or chitosan was significantly enhanced compared to that in oils without carriers (p<0.05). In O/W emulsions, α-tocopherol loaded collagen showed higher antioxidant properties than α-tocopherol loaded chitosan (p<0.05). Collagen mesh structure and chitosan gel retarded the rates of lipid oxidation efficiently in both food matrices when α-tocopherol was not loaded. Collagen mesh structure and chitosan gel can be useful carriers for α-tocopherol in bulk oil or O/W emulsion.

Enhancing oxidative stability in heated oils using core/shell structures of collagen and α-tocopherol complex

In this study, collagen mesh structure was prepared by carrying α-tocopherol in the form of core/shell complex. Antioxidant properties of α-tocopherol loaded carriers were tested in moisture added bulk oils at 140°C. From one gram of collagen core/shell complex, 138mg α-tocopherol was released in medium chain triacylglycerol (MCT). α-Tocopherol was substantially protected against heat treatment when α-tocopherol was complexed in collagen core/shell. Oxidative stability in bulk oil was significantly enhanced by added collagen mesh structure or collagen core/shell complex with α-tocopherol compared to that in control bulk oils (p<0.05), although no significant difference was observed between oils containing collagen mesh structure and collagen core/shell with α-tocopherol (p>0.05). Results of DPPH loss in methanol demonstrated that collagen core/shell with α-tocopherol had significantly (p<0.05) higher antioxidant properties than collagen mesh structure up to a certain period. Therefore, collagen core/shell complex is a promising way to enhance the stability of α-tocopherol and oxidative stability in oil-rich foods prepared at high temperature.

Edible carboxymethyl cellulose films containing natural antioxidant and surfactants: α-tocopherol stability, in vitro release and film properties

Edible carboxymethyl cellulose films containing α-tocopherol (TC) and a mixture of polysorbate 80 (T80) and lecithin were prepared and characterized physicochemically. The stability of TC into the CMC matrix over time, the physicochemical properties of the films, in vitro release profile of TC from films and its antioxidant capacity were investigated. Films containing each one or both surfactants were more homogenous and no phase separation was observed during the drying. TC-loaded CMC films were stable over a period of 8 weeks, regardless of surfactant type. The addition of T80 in CMC films provided a plasticizing effect, reducing Young's modulus and elongation-at-break. Conversely, the presence of lecithin together with the T80 reduced the water vapor permeability to values close to pure CMC (4 × 10−7 g/h m Pa), improving the mechanical properties of the films. Lecithin-based films were able to release approximately 5 times more TC than T80-based films, probably due to differences in the interaction between surfactant and matrix. These findings also explain the higher antioxidant effect of lecithin-based films. Moreover, lecithin chemically interacts with TC, slowing down its degradation. The main contribution of this study is that combinations of surfactants are more effective to stabilize TC in a hydrophilic matrix, protecting it against degradation.

Stability of α-tocopherol, γ-tocopherol and β-carotene during ripening of pasta-filata cheese made from raw and pasteurised milk with different vitamin contents

Ripening stability of α-tocopherol, γ-tocopherol and β-carotene in cheese was evaluated in relation to different milk vitamin content and to the use of either pasteurised or raw milk. Milk from two farms with different management systems was used to obtain different vitamin content. Milk was divided into two parts, of which only one was pasteurised. Four blocks of cheese were made from each batch and ripened for 0, 15, 30, or 60 days at 14–16 °C. There was a notable variation in cheese vitamin levels, with the differences in milk vitamin content due to farm management having the highest impact. Pasteurisation had no effect on cheese vitamin content. Cheese γ-tocopherol and β-carotene content decreased after 30 and 60 days, respectively, whereas α-tocopherol content remained stable. γ-Tocopherol appeared to be the most efficient antioxidant in cheese, followed by β-carotene. Vitamin stability was not influenced by milk vitamin content or pasteurisation.

Effect of resveratrol or ascorbic acid on the stability of α-tocopherol in O/W emulsions stabilized by whey protein isolate: Simultaneous encapsulation of the vitamin and the protective antioxidant

Food proteins have been widely used as carrier materials due to their multiple functional properties. Hydrophobic bioactives are generally dissolved in the oil phase of O/W emulsions. Ligand-binding properties provide the possibility of binding bioactives to the protein membrane of oil droplets. In this study, the influence of whey protein isolate (WPI) concentration and amphiphilic resveratrol or hydrophilic ascorbic acid on the decomposition of α-tocopherol in the oil phase of WPI emulsions is considered. Impact of ascorbic acid, in the continuous phase, on the decomposition depended on the vitamin concentration. Resveratrol partitioned into the oil–water interface and the cis-isomer contributed most of the protective effect of this polyphenol. About 94% of α-tocopherol and 50% of resveratrol were found in the oil droplets stabilized by 0.01% WPI. These results suggest the feasibility of using the emulsifying and ligand-binding properties of WPI to produce carriers for simultaneous encapsulation of bioactives with different physicochemical properties.

Effects of relative humidity and neutral emulsifier on oxidative stability of corn oil during room temperature storage

The effects of tween 20, one of neutral emulsifiers, on oxidative stability of corn oil were determined under a relative humidity (RH) range of 0–93 % at room temperature after 350 days of storage. The degree of oxidation was determined by headspace oxygen content and conjugated dienoic acids analyses. Moisture content and α-tocopherol were also analyzed. The degree of lipid oxidation was significantly influenced by the concentration of tween 20 and relative humidity. Samples without addition of tween 20 showed the highest oxidative stability in 11 % RH, whereas oxidative stability was lowest at 93 % RH. Adding 0.5 and 1.0 % tween 20 increased the rate of lipid oxidation in a concentration dependent manner. Samples containing tween 20 had higher moisture content than those without an amphiphilic compound. Stability of α-tocopherol was depending on the content of moisture and amphiphilic compounds in bulk oil.

Effects of relative humidity on the antioxidant properties of α-tocopherol in stripped corn oil

The effects of relative humidity (RH) on the antioxidant properties of α-tocopherol (10, 20, 42, and 84ppm) were determined in stripped corn oil oxidised at 60°C. The degree of oxidation in oils was determined by analysing headspace oxygen content and conjugated dienoic acids (CDAs). Changes in moisture and α-tocopherol content were also monitored. The oxidative stability of stripped corn oil and stability of α-tocopherol differed significantly depending on the RH. As the concentration of α-tocopherol increased from 10 to 84ppm, oxidative stability decreased significantly irrespective of RH. The remaining α-tocopherol content decreased as RH increased, suggesting an important role for moisture content in the stability of α-tocopherol. Antioxidant properties of α-tocopherol were greatly influenced by both moisture content in oil and α-tocopherol concentration.