Stability Of Retinol Research Articles

Silica Microparticles from Sugarcane By-Products as an Encapsulation System for Retinoids Aimed at Topical Sustained Release.

The encapsulation of retinol within silica microparticles has emerged as a promising opportunity in the realm of cosmetic and pharmaceutical formulations, driven by the need to reinforce the photoprotection and oxidation stability of retinol. This work examines the process of encapsulating retinol into silica microparticles. The association efficiency, microparticle size, molecular structure, morphology, oxidation, and release profile, as well as biocompatibility and skin sensitization, were evaluated. Results showed that 0.03% of retinol and 9% of emulsifier leads to an association efficiency higher than 99% and a particle size with an average of 5.2 µm. FTIR results indicate that there is an association of retinol with the silica microparticles, and some may be on the surface. Microscopy indicates that when association happens, there is less aggregation of the particles. Oxidation occurs in two different phases, the first related to the retinol on the surface and the second to the associated retinol. In addition, a burst release of up to 3 h (30% free retinol, 17% associated retinol) was observed, as well as a sustained release of 44% of retinol up to 24 h. Encapsulation allowed an increase in the minimal skin cytotoxic concentrations of retinol from 0.04 μg/mL to 1.25 mg/mL without skin sensitization. Overall, retinol is protected when associated with silica microparticles, being safe to use in cosmetics and dermatology.

An eco-friendly system for stabilization of retinol: Astep towards attending performance with improved environmental respect.

Retinol (Vitamin A) is one of the most effective molecules for the treatment of skin aging. However, it degrades rapidly under the influence of light, oxygen, metal ions, and oxidizing agents. To prevent this, stabilizing systems are used commonly. Notably, butylated hydroxytoluene (2,6-di-tert-butyl-p-cresol) (BHT) and ethylenediaminetetraacetic acid (EDTA) salts exhibit excellent antioxidant and metal-chelating properties but are not eco-friendly. In this study, our goal was to develop a new eco-friendly stabilization system for retinol-based formulations such that the system does not interfere with retinol skin absorption, nor its clinical efficacy. An evaluation tool called the Sustainable Product Optimization Tool (SPOT) was used to assess the environmental performance of formulations containing retinol and the various stabilizers investigated. Accelerated stability tests were performed on formulations stored for 2 months at 4 and 45°C (ISO/TR Standard 18811 2018 directives). Long-term stability evaluation was done on formulations stored for 24-months at room temperature. Retinol skin absorption was assessed by the Franz cell method using human skin explants (OECD guideline 428). Finally, a clinical study was performed to evaluate the cosmetic performance of a 0.3% stabilized retinol formulation. N,N'-ethylenediamine disuccinic acid ([S,S]-EDDS isomer) and pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate) (PBHC) showed higher biodegradability and a reduced water footprint compared with those of BHT and EDTA. The SPOT simulation gave [S,S]-EDDS + PBHC a score of 10 versus 8.84 for EDTA + BHT. Moreover, [S,S]-EDDS + PBHC better controlled the chemical degradation of retinol compared with EDTA + BHT. Retinol skin absorption was also achieved in the case of a formulation containing [S,S]-EDDS + PBHC, and several skin attributes improved significantly after 12 weeks of product use, with over 75% of the panel perceiving benefits. Regarding retinol stabilization, the PBHC + [S,S]-EDDS combination is an eco-friendlier and more effective alternative to BHT + EDTA.

Stability of retinol in liposomes as measured by fluorescence lifetime spectroscopy and FLIM

Retinol shows complex photophysical properties that make it potentially useful as an exogenous or endogenous probe of membrane microenvironment, but it has not been fully explored. In this study, we use bulk fluorescence lifetime measurements and fluorescence lifetime imaging microscopy (FLIM) to examine the stability of retinol in phosphatidylcholine (PC) multilamellar and unilamellar vesicles with and without cholesterol. We find that both light and exposure to ambient temperature and oxygen contribute to retinol degradation, with the addition of an antioxidant such as butylated hydroxytoluene (BHT) essential to provide stability, especially in the absence of cholesterol. With exposure to ultraviolet light to excite its native fluorescence, retinol degrades rapidly and can photosensitize vesicles. Degradation can be measured by a decrease in fluorescence lifetime. In POPC vesicles without cholesterol, BHT leads to initially higher lifetimes compared with no BHT, but it increases the rate of photodegradation. The presence of 10 mol % cholesterol protects against this effect, and vesicles with 20 mol % cholesterol show longer lifetimes without BHT under all conditions. Because of its environmental sensitivity, retinol is interesting as a FLIM probe, but careful controls are needed to avoid degradation, and additional work is needed to optimize liposomes for food and cosmetic applications.

Effect of Storage Condition on Retention of Vitamins in Selected Commercial Fortified Maize Flour in Kenya

Food fortification is one strategy that has been used to overcome micronutrient deficiencies among vulnerable populations. Maize, a common staple food in Kenya, has been used as a suitable fortification vehicle. However, several factors, including storage conditions, impact micronutrient stability in fortified maize flour.This study aimed to to assess the influence of storage condition on the retention of retinol and B-vitamins in selected commercial fortified maize flour. Fresh samples of fortified maize flours from two brands (coded XX1 and XY2) were sampled from the manufacturers at the point of production. The storage stability of retinol and B-vitamins in the two brands (XX1 and XY2) was monitored for 6 months at 25 °C/ 75 % relative humidity and 35 °C/ 83 % relative humidity. Retinol and thiamine were the least stable vitamins in both flour brands, while riboflavin and folate were relatively stable. Niacin was the most stable vitamin. Retinol was the least stable vitamin for brand XXI at both 25 °C/75% RH and 35 °C/83% RH, followed by thiamine, riboflavin, folate, and niacin. However, brand XY2 showed that under both storage conditions, thiamine was the least stable vitamin, followed by retinol, riboflavin, folate, and niacin. Vitamin retention was higher in samples stored at a lower temperature and relative humidity (25 °C/ 75 % RH) than in samples stored at higher temperature and relative humidity (35 °C/ 83 % RH) for both brands. In conclusion, thiamine and retinol were generally more susceptible to storage losses. Although the vitamin content in the flour samples decreased during storage, the changes in both storage conditions (except for riboflavin) and both brands were not significantly different.

33252 Novel antiaging retinol complex improves facial photodamage in a Hispanic and Caucasian population

Retinol continues to be a key ingredient to improve facial photodamage. However, retinol stability in convenient and affordable consumer formats - such as day and night cream jars - has been a formulation challenge which can lead to a loss in retinol potency and product discoloration. An antiaging night cream was developed with a novel retinol complex, including a proprietary stabilizing oil system which maximizes retinol potency, pro-ceramides and niacinamide. The objective of this research was to demonstrate efficacy of the novel retinol complex in a mixed Hispanic and Caucasian population.

698 Retinol: A better solution for skin anti-aging than retinyl palmitate

The retinoids are a well-known anti-aging ingredients that show a clinical efficacy for wrinkle improvement. Retinol has been applied to many products as a representative ingredient for skin anti-aging cosmetics for many years. Recently, the use of retinol derivatives such as retinyl palmitate or retinyl propionate is increasing. The introduction of these derivatives is intended to use a more stable and to lower the risk of skin irritation. However, a technology to increase the stability of retinol has been developed and the problem has been sufficiently overcome. In this study, we conducted experiments comparing retinol and retinyl palmitate, a well-known retinol alternative, regarding the efficacy on skin anti-aging related markers in vitro. The efficacy of retinol on procollagen I expression, a representative dermal component for skin elasticity was increased in a dose-dependent manner in normal fibroblasts. Retinyl palmitate also induced procollagen I expression, but the effect of retinol was higher significantly. As a result of evaluating hyaluronic acid(HA) expression in normal keratinocytes, retinol showed a significant increase in HA secretion whereas retinyl palmitate did not induce HA secretion. The expression of MMP-1 increased by TNFα was reduced when retinol was treated, and retinyl palmitate had no inhibitory effect. Therefore, the efficacy of retinol was confirmed even in inflammatory aging in this study. In terms of antioxidant efficacy, retinyl palmitate had a lower radical scavenging activity compared to the high radical scavenging activity of retinol. Although not shown in this study, the antioxidant efficacy of retinol was superior to that of retinyl propionate. In conclusion, retinol can be expected to have an obvious effect than its derivatives by affecting the skin anti-aging targets. Retinol is a still attractive anti-aging ingredient in cosmetics.

Synthesis of Retinol-Loaded Lipid Nanocarrier via Vacuum Emulsification to Improve Topical Skin Delivery.

Retinol has been widely used as an anti-wrinkle active ingredient in cosmetic fields. However, the oxidation of retinol by air was one of the critical problems for application in the skincare field. In this study, Retinol-loaded lipid nanocarriers were prepared via the vacuum emulsification method to increase the stability of retinol vulnerable to air and optimized encapsulation conditions and to increase the penetration efficiency into skin. Optimizing the components of lipid nanocarriers, gradients of carbon chain C8-22 using various lipid species which made the amorphous structure and enough spaces to load retinol inside the capsules were estimated from the lower enthalpy change and peak shift in DSC analysis. The vacuum-assisted lipid nanocarriers (VLN) could help suppress oxidation, which could have advantages to increase the thermal stability of retinol. The retinol-loaded VLN (VLN-ROL) had narrow size distribution under 0.3 PDI value, under 200 nm scaled particle size, and fully negative surface charge of about -50 mV for the electrostatic repulsion to avoid aggregation phenomenon among the lipid nanoparticles. It maintained 90% or more retinol concentration after 4 weeks of storage at 25, 40 and 50 °C and kept stable. The VLN-ROL-containing cream showed improved penetration efficiency applied to porcine skins compared to the commercial retinol 10S from BASF. The total amount of retinol into the skin of VLN-ROL (0.1% of retinol) was enhanced by about 2.2-fold (2.86 ± 0.23 μg) higher than that in 0.1% of bare retinol (about 1.29 ± 0.09 μg). In addition, applied on a 3D Human skin model, the epidermal thickness and the relative percentage of dermal collagen area effectively increased compared to the control and retinol, respectively. Additionally, the level of secreted IL-1α was lower and epidermal damage was weaker than commercial product A. This retinol-loaded lipid nanocarrier could be a potentially superior material for cosmetics and biomedical research.

Comparing the stability of retinol in liposomes with cholesterol, β-sitosterol, and stigmasterol.

In this study, cholesterol (CH), β-sitosterol (SI), and stigmasterol (ST) were explored to improve the stability of retinol in the liposome bilayer. Retinol was incorporated into liposomes composed of soybean-derived L-α-phosphatidylcholine (PC) and 10% sterol (w/w), which were prepared as multilamellar vesicles. Under all conditions, the efficiency of retinol incorporation into liposomes was higher than 99%, and the average particle size of liposomes was similar to that of PC alone. Liposomes were stored at 4 and 25°C, with and without light, respectively, for 10days. It was found that during the storage, CH and SI were effective in stabilizing the retinol in liposomes. These results indicate that an appropriate phytosterol could improve the stability of retinol in liposomes.

고분자 마이셀을 이용한 레티놀 제형개발: 레티놀 안정성

레티놀은 빛, 열 및 산소에 대해 불안정하다는 특징이 있어 레티놀에 대한 안정화 기술이 계속해서 요구되고 있다. 이러한 추세에 따라 안정성이 개선된 레티놀 폴리머 마이셀 연구를 수행하게 되었다. 레티놀 조성에 산화방지제를 함량별 첨가하였고 입도 측정, 장기 및 가속 안정성, 피부투과 등 실험을 진행하였다. 입자 크기는 산화방지제 함량에 따라 차이를 나타내었다. 이 중 레티놀과 butylated hydroxyanisole(BHA) 비율이 1:1인 M3 조성은 80.83% 및 81.18%의 장기 및 가속안정성을 나타내었다. 이 제형을 대상으로 피부투과 실험을 진행하였을 때, 대조군으로 사용된 S1보다 M3의 피부투과율(52.8%)이 더 크게 나타났다. 종합적으로 레티놀 안정성을 개선할 수 있는 산화방지제와 계면활성제의 적합한 비율을 확립하였다.

Characterization of Retinol Stabilized in Phosphatidylcholine Vesicles with and without Antioxidants.

Retinol stability has been reported to be improved by encapsulation in liposomes, both with and without cholesterol. However, this improvement is limited because of lipid peroxidation. In this study, we compare the stability of retinol in phosphatidylcholine liposomes under ultraviolet (UV) light or standard room air, with and without the addition of antioxidants. Both butylated hydroxytoluene (BHT) and a proprietary mix (StoppOx) improved the shelf stability from <10 to over 30 d. The addition of cholesterol had no effect. Fluorescence imaging showed a heterogeneous distribution of retinol within the vesicles, including within the aqueous layer. Fluorescence lifetimes were equally heterogeneous. Under UV irradiation, StoppOx protected retinol for significantly longer than BHT and via different mechanisms. This suggests that natural antioxidants work well to improve the retinol stability, but that further work to determine the optimal vesicle structure remains to be performed.

A Novel LC-MS/MS Method for Improving Long-Term Stability of Retinol in Dried Blood Spots and Quantification of Its Levels

Abstract Objectives To establish an accurate and reliable method for stabilizing vitamin A (retinol) in Dried blood spots (DBS), quantifying and comparing DBS retinol concentrations with their equivalent plasma retinol levels. Methods Antioxidants pretreated on paper combined with vacuum treatment were used to increase retinol stability on DBS. A surrogate matrix of whole blood prepared using mixture of human erythrocytes and 2% BSA in PBS was firstly used in DBS retinol determination based on the fact that retinol is excluded from erythrocytes. Results DBS retinol was stable during 120 min of air drying and 30 days of room-temperature storage. The method was linear in the concentration range of 0.04–300 μg/mL. Accuracy was calibrated using two National Institute of Standards and Technology (NIST) calibrants generated serum at concentrations of 0.1962 and 0.3948 g/mL, relative errors (RE% values) of 0.07% and 4.95% were found, respectively. Both the between-run (n = 5) and within-run (n = 6) precision (relative standard deviations, RSD%) were below 8.42%. The spiked recoveries at 3 concentrations ranged from 86.48% to 98.13%. A reliable calibration model was first developed to convert DBS retinol concentration to the equivalent plasma retinol concentration. Conclusions The validated method can be applied to the nutritional assessment of vitamin A, using the established calibration model, DBS retinol can compare with clinical reference ranges and with studies using serum or plasma samples. Funding Sources The National Key Research and Development Program of China (2018YFC1002503); The National Natural Science Foundation of China (Grant No. 81,400,848, 81,701,441); The CAMS Initiative for Innovative Medicine (2016-I2M-1–008); The Beijing municipal program of medical research (Grant No. 2016–04); The National Key Research and Development Program of China (No. 2016YFC1306204).

Effect of storage on retinol content and total antioxidant capacity of human milk

PurposeThe purpose of this paper is to evaluate the effect of different times and freezing temperatures on the antioxidant activity of raw human milk (HM) and the impact of light by different packaging on retinol level and the antioxidant activity of pasteurized HM.Design/methodology/approachDonor milks were homogenized to form the pool of the experimental study characterized by the evaluation of the effects of time (0, 2, 4, 8 and 15 days) freezing temperatures (−3°C, −8°C and −18°C) and the interference of the type of packaging on the antioxidant activity and retinol levels of HM.FindingsThe existing studies do not reveal the real impact of HM storage conditions adopted by human milk banks (HMB) in Brazil on their compounds, mainly in relation to the effects of temperature and freezing time and the incidence of light on retinol levels and antioxidant activity. In view of the already documented importance of these compounds for the growth, development and health of children, it is extremely important to assess their stability according to the procedures adopted by the banks. It has been observed in this study that lower freezing temperatures (−18°C) further preserve the antioxidant activity. It was found that the amber and transparent vials wrapped with aluminum foil allowed for greater retinol stability of HM, with values of 2.501±0.757 µmol/L and 4.991±0.825 µmol/L, respectively. On the contrary, there was no significant influence on antioxidant activity.Originality/valueIt is suggested that HMB store milk at lower temperatures and use glass jars that block the passage of light.

Improving long-term stability of retinol in dried blood spots and quantification of its levels via a novel LC-MS/MS method.

Vitamin A deficiency (VAD) is a major micronutrient deficiency in children. Although plasma and serum retinol levels are proposed as the key indicators of VAD, collecting and transporting plasma and serum are difficult and inconvenient in field studies. Dried blood spot (DBS) retinol has been used as an alternative to plasma retinol in several epidemiological and clinical studies. A limitation of methods that use DBS retinol is the instability and apparent loss of retinol in DBSs. Therefore, an accurate, reliable method for stabilizing retinol in DBSs and quantifying and comparing DBS retinol concentrations with equivalent plasma retinol levels is required. In this study, antioxidants on paper combined with vacuum treatment were found to greatly increase the stability of DBS retinol during 120min of air drying and 30days of room-temperature storage. A surrogate matrix of whole blood prepared using a mixture of human erythrocytes and 2% BSA in PBS was firstly used in DBS retinol determination based on the fact that retinol is excluded from erythrocytes. The method was linear in the concentration range of 0.04-300μg/mL. Both the between-run (n = 5) and within-run (n = 6) precision (relative standard deviations, RSD%) were below 8.42%. The spiked recoveries at 3 concentrations ranged from 86.48 to 98.13%. The internal standard (IS)-normalized matrix factor (MF) was 99.72% with a RSD% of 10.50% (n = 3). The accuracy was calibrated using two National Institute of Standards and Technology (NIST) serum-generated calibrants at concentrations of 0.1962 and 0.3948g/mL, and relative errors (RE% values) of 0.07% and 4.95% were found, respectively. A simple calibration model was first developed to convert DBS retinol concentration to the equivalent plasma retinol concentration, thereby enabling comparisons with clinical reference ranges and with studies using serum or plasma samples. Graphical abstract.

UV and storage stability of retinol contained in oil-in-water nanoemulsions

This study was performed to examine the stability of retinol contained within oil-in-water (O/W) emulsions under UV and during storage at different temperatures. O/W emulsions were prepared using different emulsifiers and oil concentrations. The stability of the retinol contained in the O/W emulsions was investigated by measuring the percentage of residual retinol in the samples after UV exposure and storage at different temperatures (4, 25, and 40 °C). The oil concentration of the emulsion had a greater impact on UV stability than the type of emulsifier used, whereas the storage stability at different temperatures was affected by both the choice of emulsifier and the oil concentration. The storage stability of the retinol contained in the O/W emulsions may be related to the lipid oxidation properties of the emulsions rather than the latter’s physical stability. Experiments with EDTA and different oil types were performed to confirm this theory.

SmartLipids® as third solid lipid nanoparticle generation - stabilization of retinol for dermal application.

smartLipids® as the 3rd lipid nanoparticle generation are made from a complex lipid mixture. The chaotic particle matrix structure provides higher loading with actives and a firmer inclusion inside the particle matrix being more protective for chemically labile molecules. Thus, these particles were used to develop an optimized retinol formulation. As a new approach, the old concept of the core-shell SLN particles was combined with the novel smartLipids® technology as new stabilization model. Particles were produced by hot high pressure homogenization, loaded with increasing amounts of retinol (5%, 15%, 20%), and both the physical (size, crystallinity) and chemical stability were monitored. According to the core-shell model, the retinol precipitates first, forming a core. Then, in the final solidification stage of the particles the retinol core gets surrounded by a shell of lipid-retinol eutectic mixture. With increasing retinol content, more retinol precipitates in the core and is chemically protected. The model was confirmed by the stability data obtained, e.g. with 5%, 15% and 20% retinol loading, after 60 days of storage 37%, 59% and 75% of retinol remained in the particle suspensions. Thus, chemical stability increased with loading. Size remained unchanged at about 200 nm. Crystallinity showed absence of polymorphic transitions, which can cause expulsion of active from the particle matrix, leading to degradation. After incorporation of the particles into a gel as dermal formulation, similar stability was observed. The developed concept can be transferred to other chemically labile dermal actives, in cosmetics and pharma.

Effect of layer-by-layer coatings and localization of antioxidant on oxidative stability of a model encapsulated bioactive compound in oil-in-water emulsions

Oxidation of encapsulated bioactives in emulsions is one of the key challenges that limit shelf-life of many emulsion containing products. This study seeks to quantify the role of layer-by-layer coatings and localization of antioxidant molecules at the emulsion interface in influencing oxidation of the encapsulated bioactives. Oxidative barrier properties of the emulsions were simulated by measuring the rate of reaction of peroxyl radicals generated in the aqueous phase with the encapsulated radical sensitive dye in the lipid core of the emulsions. The results of peroxyl radical permeation were compared to the stability of encapsulated retinol (model bioactive) in emulsions. To evaluate the role of layer-by-layer coatings in influencing oxidative barrier properties, radical permeation rates and retinol stability were evaluated in emulsion formulations of SDS emulsion and SDS emulsion with one or two layers of polymers (ϵ-polylysine and dextran sulfate) coated at the interface. To localize antioxidant molecules to the interface, gallic acid (GA) was chemically conjugated with ϵ-polylysine and subsequently deposited on SDS emulsion based on electrostatic interactions. Emulsion formulations with localized GA molecules at the interface were compared with SDS emulsion with GA molecules in the bulk aqueous phase. The results of this study demonstrate the advantage of localization of antioxidant at the interface and the limited impact of short chain polymer coatings at the interface of emulsions in reducing permeation of radicals and oxidation of a model encapsulated bioactive in oil-in-water emulsions.

Improved oxidative barrier properties of emulsions stabilized by silica–polymer microparticles for enhanced stability of encapsulants

The materials encapsulated within oil-in-water emulsions are prone to oxidation due to the permeation of oxidative species across the oil–water interface and into the lipid phase. Thus, the oxidative barrier properties of the interfacial layer are pivotal in reducing oxidation within emulsified oils. To enhance these barrier properties, we explored an approach of stabilizing emulsions using ‘silica–polymer microparticles’. We hypothesize that these microparticles will enhance the barrier properties of emulsion interfaces by mechanisms such as higher interfacial thickness and quenching of oxidative species before they permeate into the emulsions. Silica–ε-polylysine (Si–EPL) microparticles were synthesized by electrostatic aggregation of anionic silica nanoparticles and cationic ε-polylysine in the aqueous phase. Formation of Si–EPL microparticles was validated using particle size, ζ-potential and scanning electron microscopy measurements. These microparticles were subsequently used for emulsion stabilization. Emulsions stabilized by silica nanoparticles alone were used as control. Oxidative barrier properties were determined by measuring the rate of permeation of peroxyl radicals from the aqueous to the oil phase of the emulsion using fluorescence based methods. The rate of permeation of peroxyl radicals was significantly lower in emulsions stabilized by Si–EPL microparticles compared to that stabilized by silica nanoparticles. One of the mechanisms responsible for the observed effect was enhanced quenching of peroxyl radical by Si–EPL microparticles before they can permeate inside the oil phase. To further validate the results, stability of a model bioactive compound, retinol, encapsulated in these emulsions was compared. Consistent with peroxyl radical permeation measurements, emulsion stabilized by Si–EPL microparticles significantly improved the oxidative stability of retinol compared to that stabilized by silica nanoparticles alone. Thus, by engineering the physical properties of the interfacial layers, the oxidation of the encapsulants in emulsions can be controlled.

Role of oxygen scavengers in limiting oxygen permeation into emulsions and improving stability of encapsulated retinol

The oxidation reactions significantly limit quality and shelf life of food products. The overall goal of this study was to evaluate the relative efficiency of selected oxygen scavengers in limiting oxygen permeation into the oil phase of the emulsion and its impact on stability of encapsulated model bioactive compound. Sodium sulfite (Na2SO3), glucose oxidase+catalase (GOx+catalase) and ascorbic acid (AA) were evaluated as water-soluble oxygen scavengers. The results show that GOx+catalase was approximately 6 times more effective in improving stability of retinol encapsulated in the oil phase of the emulsion than Na2SO3. Na2SO3 reduced the rate of permeation of oxygen into the oil phase of the emulsion by approximately 2.5 times as compared to the control emulsion but was not effective in limiting degradation of retinol encapsulated in the emulsion. AA was not effective in limiting oxygen permeation into the emulsion. This study demonstrates the potential of oxygen scavengers in limiting oxygen permeation in emulsion and their impact on improving oxidative stability of encapsulated bioactives.

Effect of barrier properties of zein colloidal particles and oil-in-water emulsions on oxidative stability of encapsulated bioactive compounds

BackgroundOxidation of encapsulated bioactive compounds is a key challenge that limits shelf-life of bioactive containing products. The objectives of this study were to compare differences between the oxidative barrier properties of biopolymer particle based encapsulation system (zein colloidal particles) and oil-in-water emulsions and evaluate the impact of these differences on oxidative stability of encapsulated bioactives. MethodsBoth zein colloidal particles and oil-in-water emulsions were stabilized by casein protein. The oxidative barrier properties of the selected encapsulation systems were determined by measuring the permeation rate of peroxyl radicals and oxygen across the interface. Peroxyl radical permeation rates were correlated with stability of a model bioactive, curcumin and oxygen permeation rates were correlated with stability of another model bioactive, retinol. ResultsRadical permeation rate was significantly higher in oil-in-water emulsions compared to zein colloidal particles, indicating enhanced barrier property of zein colloidal particles against peroxyl radical induced oxidation. Consistent with these results, stability of curcumin encapsulated in zein colloidal particles was significantly higher compared to that in oil-in-water emulsions. Oxygen permeation measurements showed no significant differences in the barrier properties of both encapsulation systems against oxygen permeation. Consistent with these results, the oxidative stability of retinol was similar in both encapsulation systems. ConclusionsThe results of this study demonstrate the advantages of biopolymer particle based encapsulation system in limiting free radical induced oxidation of encapsulated bioactives and also demonstrate the ineffectiveness of both encapsulation systems in limiting oxygen permeation.

Effect of Polymer Characteristics on the Thermal Stability of Retinol Encapsulated in Aliphatic Polyester Nanoparticles

The present study investigates how the thermal stability of retinol (vitamin A) encapsulated in polyester nanoparticles is influenced by the types of polyester used for the nanoparticles. A variety of polyester-retinol nanoparticles were prepared with various polyesters like: poly(ethylene adipate), PEA; poly(butylene adipate), PBA; poly(hexamethylene adipate), PHMA; and three polycaprolactones, PCL, of different molecular weights (<TEX>$M_n$</TEX> ~10, 40, and 80K). The chemical stability of retinol in these nanoparticles, monitored in an aqueous solution at <TEX>$25^{\circ}C$</TEX> and <TEX>$40^{\circ}C$</TEX> for 4 weeks, was high in the following order of the nanoparticles prepared with PHMA > PCL 40K > PCL 10K > PCL 80K > PBA~PEA at <TEX>$25^{\circ}C$</TEX> and PCL 10K > PCL 40K > PHMA > PCL 80K > PEA > PBA at <TEX>$40^{\circ}C$</TEX>. More importantly, this study has also found that the thermal stability of the retinol in the nanoparticles was closely connected with the melting temperatures of polyesters and polyester nanoparticles. The results were further discussed with possible factors - such as sample preparation condition (or history) and miscibility between the polyesters and retinol - affecting <TEX>$T_m$</TEX> of the polyesters and the nanoparticles.