Characterization Of Microcapsules Research Articles

Microencapsulation of Saffron Petal Phenolic Extract: Their Characterization, In Vitro Gastrointestinal Digestion, and Storage Stability.

Saffron petal, as a byproduct of saffron processing, contains a considerable amount of antioxidant compounds. In the present study, the effect of drying methods (spray and freeze) and different wall structures (maltodextrin and pectin) was investigated on the physicochemical characteristics of microcapsules of saffron petal extracts. Results showed that the increase of the pectin ratio in wall composition leads to the increase of polyphenols content and antioxidant activity of microcapsules. Microencapsulation efficiency and loading capacity in pectin-contained samples were higher than pure maltodextrin samples. Moreover, microcapsules obtained from spray drying method had higher microencapsulation efficiency and loading capacity in comparison with microcapsules obtained from freeze drying method. Also, scanning electron microscopy, X-ray diffraction, and differential scanning calorimetry have been shown to be useful tools for establishing the difference between produced microcapsules. High-performance liquid chromatography was used to evaluate the polyphenolic compounds of the microsphere. The chromatograms obtained from both encapsulation methods indicated high levels of routine in microcapsules of saffron petal extract. In addition, the release of polyphenols from microcapsules of saffron petal extract was evaluated under simulated gastrointestinal conditions. The results indicated that the release behavior of the microcapsules varied according to the type of drying method and wall composition. To assess the shelf life, the microcapsules were kept at different temperatures and relative humidities for 16 weeks. The microcapsules produced by freeze drying and containing high levels of pectin in wall composition had the highest antioxidant activity when kept in relative humidity of 11% and temperature of 4 °C. PRACTICAL APPLICATION: Saffron petal is the huge amount of saffron by-product and contains a number of various antioxidant compounds. Microencapsulation of its valuable compounds results in preventing the destruction of these compounds by environmental factors and their increased bioavailability. Indeed, this paper focuses on the release of microencapsulated powder in the simulated system of the digestive system that helps us to improve the shelf life of the final product during the process and controlled release of compounds in the food and pharmaceutical industries.

Effect of Arrowroot Nano Starch Preparation Methods on the Characteristics of Temulawak Oleoresin Microcapsules

Active compounds of temulawak often have some disadvantages such as barely dissolve in water, unstable in alkaline and acidic conditions, that need to be overcome by coating with the starch matrix. Starch nanoparticles precipitated with alcohol can serve as coating material because it has a helical hole and the porous structure. The research objective was to determine the effect of starch nanoparticles coating materials on the characteristics of temulawak microcapsule. The treatments tested included types of coating/starch matrix resulted from two different preparations of arrowroot starch nanoparticles namely by butanol and ethanol precipitation with two degrees of hydrolysis. The parameters observed consist of yield, encapsulation efficiency (EE), drug loading (DL), morphology (SEM and TEM), particle size distribution and polydispersity index (PDI), FTIR, and antioxidant activity. The results showed that the yield of microcapsules ranged from 42.91 to 58.31%, with EE from 48.69 to 69.59% and DL from 19.02 to 28.96%. Microcapsule size ranged from micro to nano size having 200 nm in average with rounded shape, and polydispersity index from 0.69 to 0.94. The antioxidant activity showed that microcapsule coated with butanol precipitation starch matrix was higher than that of ethanol precipitation. The FTIR analysis showed a binding of the active ingredient (curcumin) in the matrix as seen with the new absorption peak at a wavelength of 1510 cm−1 as well as two new peaks at 1750 cm−1 and 3730 cm−1.

Use of enzymatically modified starch in the microencapsulation of ascorbic acid: Microcapsule characterization, release behavior and in vitro digestion

Microcapsules were prepared using enzyme-treated corn starch with 16 and 20 h of hydrolysis time (ETCS 16 h-GA and ETCS 20 h-GA) and coated with gum (GA). Microcapsules made only from GA were used as control. The increase in hydrolysis time caused an increase in the number and size of pores on the corn starch. The percentage of total starch decreased with the increase in hydrolysis time, while apparent amylose increased. The starch/ascorbic acid ratio in the microencapsulation process was 1/0.1 (shell/core). Particle size to ETCS 16 h-GA and ETCS 20 h-GA were 1087.44 μm and 1245.43 μm, respectively. While that for GA microcapsules was 12.71 μm. The ETCS microcapsules showed a lower percentage of retention and surface ascorbic acid (AA) than GA microcapsules. ETCS 16 h-GA microcapsules lost less AA during storage time and provided a better protection for AA during digestion in the gastrointestinal tract (GIT); these benefits were more noticeable from day 7 of storage. ETCS can be used as a wall material, as it shows greater stability in the protection of AA and allows for a controlled release in the GIT.

A Study of the Effect of Kosmotropic and Chaotropic Ions on the Release Characteristics of Lignin Microcapsules under Stimuli-Responsive Conditions

Stimuli-responsive behavior of lignin microcapsules (LMCs) has been investigated along with the detailed characterization of their stability profiles. The disassembly of LMCs was found to be salt species-dependent, indicating the specific relevance of inherent kosmotropic and chaotropic characteristics. For the first time, a connection between the Hofmeister series and the stability profile of lignin microscale materials is established. LMCs showed excellent stability in water and under high temperature and pressure (autoclaving conditions). Active release is efficiently triggered by pH changes and balancing chaotropic and kosmotropic effects via salinity tuning.

The photoelectric properties characteristics of dye-doped nematic liquid crystal microcapsules with different structural composition

In this study, we promote a new dye-doped nematic liquid crystal (DDNLC) microcapsules system sandwiched between two ITO substrates for making an electrochromic fabric coating with both low driving voltage and wide versatility. The effects of the dye dosage, particle size and shell thickness of microcapsules on the electro-optical properties of DDNLC microcapsules were systematically investigated. Results show that optical appearance of the optimized DDNLC microcapsules can be reversibly changed between transparent and colored states by switching on and off the direct-current power. Driving voltage, response time and delay time were close related to the particle size of DDNLC core in microcapsules, and an alignment model was used to calculate the geometric construction of the microcapsules. The proposed experimental results provide reliable simulations of the electro-optical properties of DDNLC microcapsules which showing great potential applications in a wide range of uses, such as electronic paper, military camouflage coating or intelligent flexible display fabric.

Development of vanillin/β-cyclodexterin inclusion microcapsules using flax seed gum-rice bran protein complex coacervates.

Encapsulation of vanillin through β-cyclodexterin inclusion complex coacervates (β-CD-IC) was developed to achieve higher thermal stability and controlled release of vanillin. The effect of protein to polysaccharide (Pr:Ps) ratio and core (Vanillin/β-CD-IC) to wall (coacervate) ratio on the vanillin encapsulation as well as thermal, microstructural and physical characteristics of microcapsules were investigated. Microcapsules had particle size ranging from 0.75 to 4.5 μm with negative surface charge and narrow size distribution. Although particle size and encapsulation efficiency were increased by increasing the Pr:Ps ratio and core to wall ratio, the zeta-potential decreased. Vanillin/β-cyclodexterin loaded microcapsules had the maximum encapsulation efficiency about 85% at core to wall ratio of 1:3 and Pr:Ps ratio of 9:1. Structural studies by Fourier-transform infrared spectroscopy (FTIR) indicated the entrapment of encapsulant and X-Ray diffraction data and scanning electron microscopy (SEM) images showed that microcapsules have amorphous structure with soft surface. Furthermore, FTIR results indicated the formation of vanillin/β-cyclodextrin inclusion is the result of chemical interactions, but physical interaction between core and shell leads to encapsulate vanillin/β-cyclodextrin inclusion in rice bran protein-flaxseed gum (RBP-FG) coacervates. Microencapsulation increased the vanillin thermostability and its shelf life. Therefore, it is possible to increase thermal stability of vanillin against environmental conditions.

Camel whey protein microparticles for safe and efficient delivery of novel camel milk derived probiotics

Novel encapsulating matrix (whey proteins from camel and cow milk) were utilized for encapsulation of a potent probiotic strain (Pediococcus acidilactici) isolated previously from raw camel milk. The bacterial cell death, thermal tolerance, release behaviour, microcapsule characterization and bioactive properties of encapsulated probiotic strain demonstrated upon simulated gastro-intestinal digestion (SGID) conditions were studied. Micro-images showed small round shaped particles embedded in the matrix of both whey proteins while, FTIR showed the presence of characteristic peak of free cells at 1230 cm−1 in micro-capsules that confirms the encapsulation of Pediococcus acidilactici within the whey protein matrices. The bacterial death cycles after encapsulation was very less and found to be 0.94 and 1.07 log cfu/g in camel whey capsules (ECMW) and cow whey capsules (ECWW), respectively, which revealed improved viability of probiotic cells after encapsulation. ECMW offered better thermal protection to cells than ECWW, whereas ECWW showed higher viability (8.67 log cfu/g) than ECMW (7.89 log cfu/g) after SGID. Probiotic cells encapsulated in cow whey capsules (CWW) showed remarkable retention of α-glucosidase, cholesteryl-esterase and pancreatic-lipase inhibitory activity.

Fabrication and characterization of microcapsule encapsulating EOR surfactants by microfluidic technique

During the process of enhanced oil recovery (EOR), surfactants are injected underground in order to draw more oil from the reservoir. Surface active agent molecules, however, can be easily absorbed by the pore surface of the reservoir rock, causing a massive waste. This paper introduces a novel method for designing a type of microcapsule loading EOR surface activator to solve the absorption problem for surfactants injection. The approach employs microfluidic technique to generate O/W/O double emulsion templates that can be used to fabricate hollowed microcapsules coupled with free radical polymerization. Factors including emulsifier concentrations, flow rates, viscosities and densities of the inner, middle and outer fluids which can affect the formation and morphology of emulsions and microcapsules have been systematically investigated and optimized as well. Additionally, morphological analysis confirms that the as-prepared monodisperse microcapsule has the capacity of encapsulating surfactant molecules owing to its hollowed structure. Finally, the diffusion permeability of the prepared microcapsules is examined, indicating that permeability of the microcapsule membrane can be controlled by adjusting the thickness and cross-linking degree of the microcapsule membrane. Overall, this study provides controllable and versatile preparation for this kind of microcapsule with potential in the field of enhanced oil recovery. The results can also provide valuable guidance for further investigation regarding the “smart” controllable release of EOR surface active agent.

Microcapsule characterization of phenolic powder obtained from strawberry pomace

Strawberry pomace, waste of strawberry (Fragaria x ananassa) juice, is widely produced in food industry, and contains natural phenolic compounds. In this study, microencapsulation of phenolic powder obtained from strawberry pomace was achieved using different combinations of maltodextrin (MD) and gum arabic (GA). Microcapsules were prepared using a high-speed homogenizer (HSH) and a high-pressure homogenizer (HPH). During HPH, 50 and 70 MPa were chosen as pressures with different process cycles (3, 5, and 7). The objective of this research was to study the effects of different coatings, encapsulation techniques (HSH and HPH), and parameters (pressures and process cycles) on microcapsules. Microcapsules obtained after HPH had the highest encapsulation efficiencies. Process cycle had no effect in D[50] and D[32] values. Applying 70 MPa pressure resulted in higher efficiencies and smaller particle sizes. Microcapsules coated with MD:GA ratio of 6:4, prepared by HPH 70 MPa with 5 cycles had the highest efficiency. Practical applications Strawberries (Fragaria × ananassa) are widely used in food industry for juice production. It will be beneficial to develop a novel approach in the utilization of strawberry pomace as this waste contain natural phenolic compounds. Although it is crucial to consume natural phenolic compounds, they are susceptible to oxidants, light and heat. Encapsulation is an important method that is used to enhance the shelf life and stability of compounds and to prevent unwanted taste of food ingredients like phenolics. There is no study about comparison of microencapsulation of phenolic powder obtained from strawberry pomace, using different coating materials with different encapsulation techniques. The microcapsules obtained in this study are recommended to be incorporated into functional foods. The aim of the present research was to study the effects of different coating materials, different encapsulation techniques, and different parameters of high pressure homogenization on the efficiency and characterization of microcapsules of phenolic powder.

Preparation and release properties of flufiprole-loaded microcapsules with core status of solid particles, solution droplets and oil suspending agent

Our main goal was to evaluate release mechanism of microcapsules with different core status. First, flufiprole microcapsules were directly encapsulated with chitosan (CS) and sodium dodecyl sulfate (SDS) through layer-by-layer (LbL) self-assembly. The changes of process parameters on the microcapsules characteristics (zeta potential, and morphology) were investigated. Also the release trends of flufiprole were determined and fitted with mathematical models. It was revealed that releases of three types of microcapsules were all very similar, but microcapsule with solid particles and oil suspending agent reached their peak values at 36–42, 42–48 h respectively, microcapsule with solution droplets cannot reach a maximum value. In the stage of initial burst release, Higuchi model performed better with oil suspending agent and solid particles, which was in agreement with the Fick's law. Core status being solution, release curves of the pesticide corresponded to zero-order which was in agreement with dissolution mechanism. In the stage of slow release, the values of R2 for solution and solid particles were all above 0.98, betokened the release phenomenon were in line with the first-order. On the other hand, release of oil suspending agent conformed to Higuchi model.

Relation between the particle size and release characteristics of aromatic melamine microcapsules in functional textile applications.

The relation between the particle size and release characteristics of aromatic microcapsules with a melamine resin shell in functional textile applications have been investigated. Firstly, the microcapsules are characterized based on their Fourier transform infrared spectra, encapsulation efficiencies, particle size distributions, optical images, and scanning electron microscopy images. The impregnation performances of the microcapsules have been initially evaluated using image analysis. Subsequently, the impregnation efficiency and broken release characteristics are semi-quantitatively analyzed using solid-phase microextraction-gas chromatography-mass spectrometry. The analysis results show that the highest impregnation efficiency and broken release intensity could be observed when the microcapsule size was similar to the fiber diameter (25–30 μm). Eventually, the sustained release of the microcapsules over a period of 2400 h was evaluated using the weighing calculation method, and the trends were studied using the Peppas model. It was found that the microcapsule release rate slowly and continuously decreased with time, and the release rates significantly increased with the decrease in microcapsule particle size. Thus, it could be concluded that the large microcapsules exhibited better leak tightness than the small microcapsules, whereas the small microcapsules exhibited faster sustained release rates.

Microencapsulation of Citrus Grandis Peel Oil Using Interfacial Precipitation Chemistry Technique for Repellent Application.

Essential oil of Citrus family plant is known to have repellent effect against mosquito. Unfortunately, due to its high volatility effect, its repellency effect was compromised. The incorporation of essential oil in a microencapsulation formulation has been shown to help improve the stability and potency of the repellent. In this study, Citrus grandis peel oil (CGPO) was encapsulated by using the interfacial precipitation chemistry technique. The microencapsulated CGPO was then formulated into lotion form to produce topical repellent formulation. This study includes the characterization of microcapsules with regards to the morphology, size distribution, zeta potential, Fourier Transmission Infrared spectrophotometer (FTIR), and Thermogravity analysis (TGA). The effectiveness of the microencapsulated CGPO-lotion formulation against mosquitoes was evaluated in the laboratory setting. Results indicated that CGPO have been successfully encapsulated with 6.5 µm in diameter and zeta potential values, -47.9 mV. The FTIR analysis spectrum indicated the presence of interaction between the wall materials in microcapsules. The TGA analysis demonstrated that microencapsulation improved the thermal stability of CGPO. Repellency assay revealed that microencapsulated CGPO- based formulation possessed excellent effect compared with pure CGPO. In conclusion, CGPO was successfully encapsulated and the microencapsulation aid to improve the repellency effect of CGPO against mosquito bites.

Microencapsulation of anthocyanin compounds extracted from blueberry (Vaccinium spp.) by spray drying: Characterization, stability and simulated gastrointestinal conditions

This study microencapsulated anthocyanin compounds extracted from blueberry (Vaccinium spp.) by spray drying using different inlet air temperatures (120, 140 and 160 °C) and wall materials (maltodextrin DE20 and hi-maize) to evaluate the microcapsule characteristics, stability and behavior under simulated gastrointestinal tract conditions. The encapsulation efficiency, moisture content, water activity, particle size, determination of total monomeric anthocyanins, storage stability, morphology and simulated gastrointestinal conditions were analyzed as responses. The microcapsules produced with different wall materials and different inlet temperatures presented an encapsulation efficiency between 74.40 and 85.22%. The microcapsule which presented the lowest degradation constant (0.0060) and longest half-life (115.47 days) during storage was treatment T3 (9% maltodextrin DE20 and 9% hi-maize) at 140 °C. Treatment T3 also presented more uniform particles, ensuring a better protection and retention of the active material. Microencapsulation was effective in protection during storage and improved the delivery of compounds of interest under the simulated gastrointestinal conditions in comparison to the free extract during all the steps that comprised the simulated gastric system.

Characteristics and release of monosodium glutamate microcapsules obtained by spray drying

The present study aimed at investigating the characteristics of monosodium glutamate (MSG) microcapsules. Spray-drying was used to prepare the microcapsules, in which the core material (MSG) was coated with gum Arabic (GA) and maltodextrin (MD), and the weight ratio of MD with GA was 1:2. The characteristics of microcapsules were evaluated by scanning electron microscopy (SEM), moisture content, particle size, Fourier-transform infrared (FTIR), differential scanning calorimeter (DSC), thermogravimetry analysis (TGA), release behavior, the flavor, and taste in hot-pot. Few concave wrinkles were observed on the quasispheres surface of microcapsules coated with GA and MD. The particle size of the microcapsules ranged from 14.00 to 30.00 µm in the mean diameter, and moisture content was 2.08%. An FTIR study indicated a successful packet of MSG by wall materials and the formation of MSG microcapsules during spray drying. Results of DSC and TGA showed that hybrid encapsulation was conducive to the improvement of thermal stability of MSG. In the release of hot-pot study, tests of slow-release, electronic nose, and electronic tongue demonstrated that MSG microcapsules were available in hot water conditions to release. The MSG microcapsules coated with GA and MD exhibited long time for slow-release. Therefore, spraying drying is a suitable approach to manufacture slow-released powdered microcapsules.

MICROENCAPSULATION OF BERGAMOT PEEL ESSENTIAL OIL WITH GUM ARABIC AND MALTODEXTRIN BLENDS: STABILITY AND RELEASE CHARACTERISTICS OF THE ESSENTIAL OIL COMPOUNDS

Bergamot peel essential oil is a high value product which can be used in food, beverage, confectionary, and cosmetic industries. Bergamot essential oil has high volatility, so it could be easily affected by environmental factors so it should be protected with further techniques to increase its shelf-life. The aim of this study was to examine the effect of different wall material compositions on the product yield, encapsulation efficiency, physical and chemical properties of encapsulated oil powders. For this purpose, bergamot essential oil was encapsulated with gum arabic and maltodextrin (DE 12) in varying concentrations (100:0, 0:100, 25:75, 75:25, 40:60, 60:40). Then, physical and chemical (terpenoid composition) characteristics of microcapsules were evaluated. The microcapsules were stored at 25°C for 20 days and the content and stability of main aroma compounds were determined after storage. The encapsulation yield was increased when the maltodextrin ratio was increased however, gum arabic provided greater protection of essential oil composition.

Magnetically activated microcapsules as controlled release carriers for a liquid PDMS cross-linker

Injecting water into a porous oil reservoir enhances oil sweep efficiency and leads to increased oil production, but due to the occurrence of fractures in water-flooded reservoirs, excessive water production is observed. Hence, water shut-off treatments are continuously investigated, albeit currently applied plugging materials still suffer from some disadvantages such as lack of selectivity and poor mechanical strength. In this work, we introduce a new plugging material consisting of vinyl-functional PDMS microspheres and magnetically activated microcapsules. This work focuses on the preparation and characterisation of microcapsules containing magnetite nanoparticles (MNPs), and liquid cross-linker in their core. The microcapsules are prepared via a phase separation technique, and it is established that the MNPs are located inside the microcapsules and that the shell remains nonporous, in which case the cross-linker is well protected before activating the microcapsules. While exposed to an alternating magnetic field, the MNPs generate sufficient heat to soften the polymeric shell, thereby leading to the efficient release of the cross-linker; moreover, the PDMS microspheres create a strong network, due to a cross-linking reaction. It is expected that this new approach will improve significantly the plugging process of fractures in matured reservoirs, which in turn will lead to higher oil recovery rates.

Mikroenkapsulasi Antosianin Kulit Buah Kakao (Theobroma cacao L.) Dengan Metode Koaservasi Kompleks

Anthocyanin is a class of antioxidants that are widely found in the skin of cocoa fruit (Theobroma cacao L.). Anthocyanin degradation occurs not only during the extraction process from plant tissues but also during the storage process. The microencapsulation process can protect the active substance from environmental influences or improve the stability of the preparation. This study aims to characterize anthocyanin microcapsules from cocoa (Theobroma cacao L.) fruit peel using a complex coacervation method, therefore, it can provide economic value added from this plant. Anthocyanin microencapsulation was formulated using a coating of gelatin: arabic gom with different concentrations of 1:1, 3:2, and 2:1. Microcapsule characterization was organoleptic and morphological test, particle size distribution, moisture content test, absorption efficiency, recovery test, antioxidant activity of the preparation, and FTIR analysis. The results showed that extract yield was 39.82%, optimum microcapsule characterization was obtained from 1: 1 concentration with 36.65% recovery test, 80.40% absorption efficiency, and antioxidant activity with IC50 of 20.52 ppm.

Preparation and characterization of microcapsules based self-healing coatings containing epoxy ester as healing agent

Cracks caused by chemicals or mechanical forces would damage the performance of coatings leading to the coating failure. Microcapsules based self-healing smart coatings can provide automatic recovery and extend the durability of coatings. In this study, poly urea-formaldehyde microcapsules contained tall oil fatty acid based-epoxy ester as core materials were synthesized through in situ polymerization. The synthesized microcapsules were characterized by scanning electron microscope (SEM), optical microscope, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The core content of microcapsules was 67 wt. %; the average diameter of microcapsules was 101 ± 48 μm. The self-healing coatings were prepared by embedding the poly(urea-formaldehyde)-epoxy ester (PUF-epoxy ester) microcapsules into epoxy coatings. Salt spray, SEM, and electrochemical impedance spectroscopy were examined, and the self-healing coatings exhibited satisfactory self-healing property and sufficient corrosion resistance recovery.

Characteristics of Self-Healing Microcapsules for Cementitious Composites

Urea formaldehyde/epoxy resin microcapsules were prepared by an in situ polymerization method and the effect of emulsifier on the syntheses process of the microcapsules was discussed. The surface morphology of the microcapsules was observed by optical microscopy and scanning electron microscopy (SEM). Chemical structure was characterized by Fourier transform infrared spectroscopy (FTIR). Thermal stability was obtained using simultaneous thermal analysis (STA). The microcapsules were composed of urea-formaldehyde resin shell and epoxy resin core. Emulsifier played an important role in the polymerization process when the core material was packed by pre-polymer, so the effects of different emulsifiers (OP-10, SDS and SDBS) were discussed respectively. Results showed that the particle size of the microcapsules was uniform when SDBS as an emulsifier. Microcapsules showed good thermal stability below 240 °C and the initial decomposition temperature of the microcapsules was 265 °C. The core materials released after microcapsules rupturing, which could be proven by the images of SEM. When implanted in cementitious composites, complete shape of microcapsules and good interface between microcapsules and cement specimen substrate could also be observed.

Physical and chemical stability of l-ascorbic acid microencapsulated into taro starch spherical aggregates by spray drying

Taro starch spherical aggregates are potential wall material for microencapsulation of biocompounds. The present work considered microencapsulation of l-ascorbic acid into taro starch spherical aggregates. Physical and chemical characteristics of microcapsules, as well as their stability were assessed. SEM images showed spherical microcapsules produced by the aggregation of starch granules. The range Dx50 of the particle size distribution was 14.5 μm for microcapsules and 18.7 μm for taro starch spherical aggregates. The effective encapsulation efficiency was as high as 20.9%. ATR-FTIR spectrum indicated the formation of hydrogen bonds between l-ascorbic acid and starch granules surface. The degradation rate was in the range from 0.006 (13% RH) to 0.029 (72% RH) at 55 °C. The Arrhenius parameters estimated from non-linear regression were A=1.5 and Ea=15.6 kJ∙mol−1. The minimum integral entropy was observed in the activity water range 0.3–0.4 for storage temperatures between 25 and 45 °C. Taro starch spherical aggregates have the ability of retaining and preserving l-ascorbic acid at different humidity and temperature conditions.