جستجوی مقالات مرتبط با کلیدواژه "نانوامولسیون" در نشریات گروه "مهندسی شیمی، نفت و پلیمر"

Due to their high latent heat, phase change materials have can store and release a large amount of thermal energy during phase change. Meanwhile, phase change material nanoemulsions have received much attention due to their suitable heat transfer properties and high heat storage capacity. In addition to the sensible heat capacity of the carrier fluid, these materials also have the ability to store thermal energy by using the latent heat capacity of phase change materials in the form of a dispersed phase. Also, due to the large surface to volume ratio of the dispersed phase on very small scales, heat transfer accelerates in this nanoemulsion system. In the present work, a comprehensive study on the formulation, thermophysical and rheological properties of nanoemulsion phase change materials is presented, in order to provide an insight into the advantages and challenges of using these materials. In addition to the experimental investigations on emulsions stability during storage time, and under thermal cycles and shear mechanical stresses have also been discussed. The effect of droplet size, stabilizer type and dispersed phase concentration on supercooling and other rheological and thermophysical properties of nanoemulsions such as thermal conductivity and density have also been investigated in order to determine the cooling-heating rate and volume required for energy storage, respectively. Finally, the potential of phase change material nanoemulsions for the effective management of thermal energy and promoting the methods of using renewable energy in different fields has been reviewed.

Nowadays,, owing to the increasing concern about the side effects of chemical drugs and the ineffectiveness of some of them in long term consumption, the use of natural compounds as an alternative or a complementary treatment has received increasing attention. Nigella sativa (black seed) is a common herbal medicine that renowned in traditional medicine because of its anti-cancer, antimicrobial, anti-inflammatory, and antioxidant activity. It has wide applications in Iran’s food and pharmaceutical industries. The seeds of this plant contain large amounts of essential fatty acids such as linolenic acid, antioxidants and vitamins However, hydrophobic essential oil of N. sativa with low bioavailability and sustainability properties is have not been fully usable. The nanoemulsion formulation methods are widely effective approach for increase performance of lipophilic compounds. The aim of this study was to develop black seed oil into nanoemulsions formulation via ultrasonication. Variance analysis of laser light scattering data showed the lowest particle size related to samples prepared with 2% and 4% concentration of Tween 40 surfactant during 15 minutes of sonication. The images of the electron microscopy also confirmed the results of measuring the size of droplets by particle size analyzer .The effect of storage temperature on the physical stability of optimum nanoemulsions showed that these nanoemulsions were completely stable at low temperature, but became unstable at high temperature due to the increase in droplet size. Furthermore, the oxidative studying (60 days) showed that the peroxide number and anisidine value increased slightly during the storage period, which indicates the presence of effective antioxidant compounds in honey and Nigella sativa L. seed oil (NSO), which prevents the oxidation of the oil. In this study, the nanoemulsion sample containing Tween 40 surfactant with SER 4% showed high antioxidant activity .

The current work aims to compare the effect of essential oil (pure and emulsified) Nepeta glomerulosa as natural preservatives for improving the shelf life of high-fat mayonnaise during 6 weeks of storage at 35 ºC. The nanoemulsion of Nepeta glomerulosa essential oil was prepared by the ultrasound cavitation method and physical properties were determined. Soy oil was substituted by 0.5 %w/w of the Nepeta essential oil or its nanoemulsion to compare the effect of natural and chemical (BHT and sodium-benzoate/potassium-sorbate) preservatives on the chemical (pH, acidity, peroxide-value, thiobarbituric acid-reactive-substances), microbial (acid-resistant bacteria, heterofermentative lactic acid bacteria, Escherichia coli, mold and yeast content, and salmonella) and sensory properties of mayonnaise. 1,8-Cineole (26.9%), α-Pinene (7.3%), and Limonene (6.8%) were the main compounds of this essential oil. The mean droplet diameter, PDI and viscosity of Nepeta nanoemulsions were 191.95 nm, 0.255, and 1.03 cP, respectively. The addition of the essential oil (pure or emulsified) significantly improved the oxidative stability of mayonnaise. There was no significant difference between the antioxidant activity of BHT and the essential oil. Over time, a decreasing and increasing trend was observed in pH and acidity, respectively, the slope of these trends was greater in the control sample. Nepeta essential oil and benzoate/sorbate significantly delayed microbial spoilage. The antimicrobial potential of the essential oil and its nanoemulsion were comparable with benzoate/sorbate activity (P > 0.05). At the end of storage, the overall-sensory scores of the sample containing the nanoemulsion were higher than the threshold-limit (>3) while in the 5th week, the control sample was introduced as unacceptable by evaluators. Nepeta nanoemulsion showed good potential to enhance the shelf-life of mayonnaise. Using essential oil in the form of nanoemulsion, not only reduced the consumption of essential oil but the bioactivity of the essential oil was protected for a longer time.

In this study, macroemulsions and nanoemulsions of rosemary essential oil were prepared under different ultrasound treatments (0, 2.5, 5 and 10 min). The stability of macro- and nanoemulsions of rosemary essential oil during one month of storage at 4 °C was determined through particle size measurement by DLS method. The antimicrobial activity of macro- and nanoemulsions of rosemary essential oil was evaluated by two methods of well diffusion and microdilution against four pathogenic bacteria. Also, their antioxidant potential was tested by DPPH free radical scavenging activity. The results showed that with increasing the ultrasound treatment time from 0 to 10 minutes, the emulsion droplets size decreased from 148.04 nm to 98.14 nm. An increase in macroemulsion and nanoemulsions particle size was observed during storage. The results of antimicrobial tests also showed that macro and nanoemulsions of rosemary essential oil had the highest antimicrobial activity against gram-positive bacteria, especially S. aureus. In the antioxidant activity evaluation test, the IC50 index of macro- and nanoemulsions of rosemary essential oil were estimated to be 36.43 and 45.86 g/ml, respectively. Based on the results of this study, the nanoemulsion of rosemary essential oil is suggested as a natural antimicrobial and antioxidant compound for using in foods.

Due to the sensitivity of plant essential oils to molecular oxygen which, that causes oxidation and destruction of oils and changes its properties, it can be removed from the aqueous phase, during preparation of oil in water nanoemulsions. In the present study, dissolved oxygen was removed by nitrogen purging, and the thyme essential oil nanoemulsions, under subcritical water conditions (temperature 120 oC for 2 h) and using Tween 80, were prepared by two types of aqueous phases having dissolved oxygen and without that. Obtained results indicated that by removal dissolved oxygen from the aqueous phase, characteristics of the prepared nanoemulsions were improved and their mean particle size and polydispersity index decreased from 170 to 83 nm and from 0.562 to 0.2012, respectively, and zeta potential changed from -1.27 to -3.25 mV. Evaluation of the antioxidant and antibacterial activities of the prepared nanoemulsions against Streptococcus mutans, bacteria strain that causes tooth decay, also indicated that antioxidant activity of the formed nanoemulsions increased from 31.3% to 45% and their bactericidal activity, as manifested in diameter of the created clear zone, increased from 11 to 18 mm. Finally, based on obtained results and simulation of the operation conditions for the nanoemulsion preparation process, indicated that pressure of 1.7 bar was necessary and by removal dissolved oxygen from the aqueous phase consumed energy decreased from 10.01 and 8.88 kJ/h.

In this work, the mentha essential oil nanoemulsions were prepared using Tween 20-gelatin multicomponent stabilizing system as food preservative. The response surface methodology (RSM) was applied in order to study the main and interaction effects of the stabilizer components’ proportions, namely, Tween 20 (0-10 gr) and gelatin (0-10 gr) on physicochemical characteristics of obtained nanoemulsions such as average particle size, polydispersity index (PDI), turbidity, conductivity and ztea potential. It was resulted that the response-surface models were significantly (p < 0.05) fitted for studied response variables and could precisely predict all response changes with high coefficients of determination (R2 > 0.90). The overall optimum region with minimum z-average, PDI, turbidity, conductivity and maximum range of zeta-potential was achieved at 8 gr of tween 20 and 2 gr of Gelatin. The optimum mentha essential oil nanoemulsion showed good antibacterial activity against both E. coli and S. areus, alone as well as incorporated in edible coating formulations. The maximum inhibition zone was observed using 1% carboxymethyl, 0.5% glycerol and 5% optimized nanoemulsion.

In recent years, much consideration has been paid to use of essential oils and aromatic plants with anti-oxidant and antimicrobial properties in the food and pharmaceutical industries because of increasing in consumers’ tendency in using foods without Chemical preservative. However, the essential oils are volatile compounds, sensitive towards heat and insoluble in water, which limits their application. Therefore, this study aimed to investigate the capability of encapsulation technique as a suitable method for protecting essential oil against environmental conditions and assessing the colloidal properties of nanocapsules. For this purpose, identification of active compounds of Citrus Limon L. essential oil was performed using Gas Chromatography (GC). Then, Oil-in-water emulsion with a ratio of 1: 4 Essential oils: coatings with chitosan and modified starch with different ratios (0.5: 9.5, 1: 9 and 1.5: 8.5 % w/v) using freeze drying method was prepared by sonication. The effect of different wall concentrations on the physical and chemical properties of emulsion and nanocapsules were measured. The results showed that increasing in chitosan concentration resulted in higher stability and viscosity of nano-emulsion prepared with 1.5: 8.5% chitosan: Modified starch. Nano-emulsion which coated with higher concentration of chitosan showed smaller droplets and more uniform size distribution than the other treatments. The study of nano-capsule properties determined a significant difference (P≤0.05) based on the different ratios of wall materials on moisture content, encapsulation efficiency and particle size. The morphology of the nanocapsules confirmed that the capsules with higher encapsulation efficiency had smooth surfaces, without gaps and with the least porosity.

In this research, Nanoemulsions of water droplets in gas oil have been prepared using combination of nonionic surfactants. Three formulations of the emulsion containing various amount of water as 5, 10 and 14 volume fractions (based on 100 volume fractions of gas oil) have been prepared, clear and stable, using a mixture of two surfactants containing sorbitan monooleate (20%) and sorbitan trioleate polyoxyethylene (20 mole ethoxylated) (80%) and adjusting the system HLB at 10. The effect of water content on droplets size, fuel calorific value, amount of gas emissions (environmental pollutants) and the exhaust gas temperature have been studied in a diesel engine, and it has been found that the amount of nitrogen oxide, soot, particulates, unburnt hydrocarbons and carbon monoxide are reduced. This study shows that the average droplet size of water formed (being 19.3-39 nanometers in this research) depends on the total concentration of surfactants and the amount of water used.