Κυριακή, 1 Δεκεμβρίου 2019

Fabrication and Characterization of Curcumin-Loaded Complex Coacervates Made of Gum Arabic and Whey Protein Nanofibrils

Abstract

In this research, gum Arabic (GA) and whey protein nanofibrils (WPN) were employed for the encapsulation of curcumin as a bioactive compound with low water solubility through the complex coacervation method. The optimum conditions for the formation of complex coacervates were found at WPN/GA weight ratio of 1:1 and pH value of 3.0. The resulting complexes showed a high ability for loading of curcumin as a bioactive cargo. Fluorescence spectroscopy showed that the curcumin was loaded in the hydrophobic core of WPN/GA coacervates. The characteristics of curcumin-loaded coacervates were also evaluated by XRD and FT-IR analysis. The curcumin-loaded complex coacervates dispersions showed a shear thinning behavior. They also showed a good surface activity which makes them excellent candidates to fabricate new functional food emulsions and beverages. The results indicated that the antioxidant activity and photo-stability of curcumin were significantly improved by encapsulation into WPN/GA complexes. A sustained-release profile also was investigated for curcumin from WPN/GA complexes in the simulated gastrointestinal conditions. This study suggested that the WPN/GA electrostatic-driven complexes can be used as efficient carriers for curcumin delivery.

Technological and Structural Properties of Oat Cookies Incorporated with Fructans ( Agave tequilana Weber)

Abstract

The beneficial effect of agave fructans on health has been demonstrated gaining popularity as a new prebiotic and functional food ingredient, however, their role as an ingredient and their technological properties is scarcely reported. This work studied the structural and quality features of doughs and cookies added with agave fructans “AF” and compared to systems added with chicory fructans “CF” or without fructans (“WF”) added, to analyse the effect of the chemical structure due to the fructan-type added. For doughs, it was found that AF lowered the water adsorption, causing a short development time and the highest stability during kneading. The texture profile analysis and rheological tests revealed that AF increased springiness and cohesiveness. For cookies, the crumb and lightness were evaluated using a computer vision system. Among the samples, AF promoted a darker and shiny crust and a more homogeneous and compact microstructure. X-ray diffraction analysis demonstrated that AF had the highest values of crystallinity. In order to provide more information about the distribution of carbohydrates (aldoses and ketoses) and gluten proteins in the cookies, a method was developed to specifically stain these molecules, and it successfully described the effect of the fructans incorporated into doughs and cookies. Results from confocal laser scanning microscopy illustrated differences in the distribution of the biopolymers stained. This research provided an improved understanding of the AF addition on the technological properties and the structure–functionally relationship of doughs and cookies, beyond the nutraceutical applications attributed to the AF.

Avocado Oil Incorporated in Ultrafine Zein Fibers by Electrospinning

Abstract

The objective of this study was to encapsulate avocado oil in ultrafine zein fibers by the electrospinning technique. Avocado oil, at concentrations of 15 and 30% (w/w), was incorporated into 20, 25 and 30% (w/v) zein polymer solutions. The polymer solutions were evaluated for viscosity and electrical conductivity. The zein fibers containing the avocado oil were evaluated for the efficiency of encapsulation, morphology and size distribution of diameter, FTIR-ATR and X-ray diffraction, as well as for the release of carotenoids in gastrointestinal conditions in vitro. At the concentration of 30% zein, continuous ultrafine fibers were obtained, without bead formation and with mean diameter distribution ranging from 618 to 971 nm, whose encapsulation efficiency was higher than 77%. The FTIR-ATR analysis showed the encapsulation of the oil, and X-ray diffraction showed the amorphous structure of the fibers. It was verified that the composite fiber of 30% of zein and 30% of oil had a release profile close to the ideal of carotenoid release under simulated gastrointestinal conditions.

Electrospun Ultrafine Fibers from Black Bean Protein Concentrates and Polyvinyl Alcohol

Abstract

In this study, ultrafine fibers were produced from black bean protein concentrates (BPCs) and polyvinyl alcohol (PVA) by electrospinning. The BPC was denatured under acidic (pH 2) or basic (pH 11) conditions. Polymer solutions containing different PVA concentrations (11% or 21%, w/v) and different BPC: PVA ratios (50:50 or 75:25, v/v) were used for fiber production. The electrical conductivity and rheological properties of the fiber-forming solutions were evaluated, as well as the morphology, size distribution, infrared spectrum, and thermal properties of the electrospun fibers. The fibers showed a homogeneous morphology and diameters ranging from 115 to 541 nm. Fibers from the solution containing BPC denatured at pH 11, 11% PVA, and 75:25 (v/v) BPC: PVA presented the lowest diameter, and those from BPC denatured at pH 2 had less beads than the fibers obtained from BPC denatured at pH 11. The solution formulation affected the thermal properties of the fibers, with weight loss increases ranging from 39.0% to 60.9%. The polymeric solutions containing PVA and BPC (whether denatured under basic or acidic conditions) resulted in ultrafine electrospun fibers with highly favorable characteristics that could potentially be used for the encapsulation of bioactive compounds and food applications.

Physical-Mechanical and Antifungal Properties of Pectin Nanocomposites / Neem Oil Nanoemulsion for Seed Coating

Abstract

Biodegradable polymers, when reinforced with nanostructures, are considered good sustainable coatings and viable alternatives to replace conventional coatings. In addition, biopesticides are also considered safe, biodegradable and environmentally friendly; therefore there is a growing interest in nanoemulsions based on phytochemical mixtures. In this context, the aim of this study is to aggregate Neem oil nanoemulsions and pectin matrices to produce nanocomposite films, as well as evaluate the nanoemulsions effect on the film properties for coating soybean seeds. Nanoemulsions were characterized assessing their average diameter and stability, while the nanocomposite antifungal, morphology, mechanical and barrier properties were analyzed. In general, the nanoemulsions had an average diameter close to 59 ± 0.61 nm, showed good stability and its addition improved film mechanical properties: reduced stiffness, resistance, and water vapor permeability, and increased extensibility. In addition, Neem oil provided antifungal properties against Aspergillus Flavus and Penicillium Citrinum. The seed coatings promoted a positive effect on the germination process of soybean seeds. Thus, antifungal nanocomposite films from renewable sources were successfully produced. The fungicidal inhibition of Neem oil as a nanoemulsion makes these new materials promising for the production of seed coatings.

Influence of Disperse Phase Transfer on Properties of Nanoemulsions Containing Oil Droplets with Different Compositions and Physical States

Abstract

The impact of the initial oil droplet composition and physical state on molecular exchange processes in mixed oil-in-water nanoemulsions was investigated. Nanoemulsions consisting of model oils (hexadecane or octadecane), non-ionic surfactant (Tween 80), and water were prepared by microfluidization. The physical state of the droplets in the nanoemulsions was varied by altering their thermal history. The evolution of oil droplet size and composition during storage was monitored using dynamic light scattering and differential scanning calorimetry, respectively. The effects of oil phase composition were examined by preparing nanoemulsions containing liquid hexadecane droplets and liquid octadecane droplets mixed together at mass ratios of 100:0, 75:25, 50:50, 25:75 or 0:100 H:O (w/w). Changes in droplet growth and composition during storage depended on the initial mixing ratio of the two kinds of droplets. The higher the proportion of hexadecane droplets present, the faster the rate of droplet growth, which was attributed to its higher water-solubility. The final droplet composition depended on the initial ratio of the different droplets. Second, the impact of droplet physical state was examined by preparing nanoemulsions containing liquid hexadecane droplets and either liquid or solid octadecane droplets. The solidification of the octadecane droplets retarded molecular exchange, but promoted droplet growth in the mixed nanoemulsions. These results may have important implications for understanding molecular exchange processes in complex colloidal dispersions that contain multiple types of oil phase.

Heat Stability of Differently Stabilized Solid Lipid Nanoparticles in the Presence of Excess Bulk Phase Protein

Abstract

In order to apply emulsion-based delivery systems to food, they have to be stable in a protein rich environment. This study investigated the stability of solid lipid nanoparticles (SLN) during heat treatment in the presence or absence of β-lactoglobulin (BLG). SLN were stabilized either by Tween 20 (TS) or by the protein itself (BS) and were enriched to a total BLG content of 56 mg/mL. The sizes of both types of SLN were initially in the range of 170 nm. The amount of free protein was determined before and after enrichment with BLG. As revealed by particle size and zeta potential measurements, a protein layer of BLG (hard corona) adsorbed on BS but not on TS. By contrast, a soft corona was formed around both BS and TS. SLN were heat treated in the presence and absence of protein and were characterized regarding size and zeta potential. According to transmission electron microscopy imaging, heating did not affect the shape of TS and BS: TS were platelets, whereas BS exhibited a spherical or platelet like shape. Upon heat treatment, the particle size of TS increased to about 3.5 fold of the initial size (to appr. 600 nm) in the presence and in the absence of excess protein. The cloudy protein layer (soft corona) around TS could thus not prevent coalescence of TS. By contrast, BS did not experience a change in particle size. Hence, by the choice of emulsifier, an encapsulation system that is stable against heat treatment can be obtained.

Water Crystallisation of Model Sugar Solutions with Nanobubbles Produced from Dissolved Carbon Dioxide

Abstract

This study was conducted to examine the influence of CO2 nanobubbles on crystallisation behaviour of water during freezing of model sugar (2–5%w/v) solutions. CO2 gas was dissolved at 0, 1000, and 2000-ppm concentrations before freezing. Carbonated sugar solutions in 50 mL plastic tubes were immersed in a pre-cooled (−15 °C) ethylene glycol bath and left to freeze at −15 °C for 90 min. When the temperature of the solutions reached 0 °C, ultrasound (US; 20 kHz) was emitted in the bath for 20 s duration through a metal horn transducer. The US wave applied in the ethylene glycol bath was expected to propagate to the sugar solutions in the tube and promote gas bubble formation from dissolved CO2, which will trigger the ice nucleation. Obtained freezing curves were analysed for nucleation time and temperature, supercooling degree, and time taken for phase change. In general, the CO2 gas promoted freezing of water, causing a noticeable shift in nucleation parameters. For example, nucleation time of 2000-ppm carbonated water coupled with sonication emission for 20 s (7.8 min) was much shorter than that of controls (pure water without any treatment = 19.1 min and US only = 14.3 min). The former initiated ice nucleation just below sub-zero temperature (−0.2 °C) whereas the onset temperature of controls (pure water without any treatment = −11.3 °C and the US only treatment = −10.3 °C). A similar effect was observed with different model sugar solutions. The current findings can be applied to refine the manufacturing process of ice-cream and frozen desserts by the food industries.

Characterization of Core-Shell Alginate Capsules

Abstract

A new droplets millifluidic/inverse gelation based process was used to produce core-shell alginate milli-capsules. Water-in-oil (W/O) emulsion dispersed phase containing Ca2+ ions was directly injected into a continuous alginate phase to generate a secondary W/O/W emulsion. Due to the cross-linking of alginate molecules by Ca2+ ions release, core-shell milli-capsules were formed with a very high oil loading. The influence of the curing time and of the storage conditions on capsules physico-chemical properties were investigated. It was first found as expected that alginate membrane thickness increased with curing time in the collecting bath. However, a plateau was reached for the higher curing times, in close relation with previous observations (Martins, Poncelet, Marquis, Davy, & Renard, 2017b) that an external oil layer surrounded the surface of W/O emulsion drops that acted as a barrier and hindered the release of aqueous CaCl2 droplets during curing time. Compression experiments on individual capsules revealed that alginate membrane thickness was inversely related to its mechanical properties, i.e. the thicker membrane, the lower surface Young modulus. Surface Young modulus ranged from 61 to 26 N/m at curing times of 3 and 45 min, respectively. This result was explained in terms of enhanced swelling properties of alginate membrane with curing time or storage conditions. Drying capsules led to much more resistant membranes due to the loss of water. Oil loading of 80 wt% was obtained for dry capsules whatever the conditions used.

Improving Hydrophilic Barriers of Encapsulated Compounds in Ca-Alginate Microgel Particles through a New Ionotropic Gelation Method for Double Emulsion Droplets

Abstract

The ability of encapsulation to protect hydrophilic–bioactive food compounds from harsh environments can be improved by strengthening the hydrophilic barriers of encapsulated food compounds in Ca-alginate microgel particles via the integration of oil into the microgels. This study introduces a one-step procedure to integrate water-in-oil (W/O) emulsion droplets directly into Ca-alginate microgels during the production using the impinging aerosols system. A water-in-oil-in-water (20 kg m−3 alginate solution) (W1/O/W2) double emulsion was prepared using a high speed homogeniser followed by a microfluidiser. The microstructure of the W1/O/W2 emulsion was analysed using optical and fluorescence microscopy. The mean diameters of the W1/O/W2 emulsion droplets and resultant microgels were in the range of 27.8–65.4 μm and 160–420 μm, respectively. Food dye was used as a proxy for a hydrophilic food compound and its release from the microgels was significantly decreased when it was encapsulated in the W/O emulsion droplets. Based on the numerical analysis, the presence of the W/O emulsion droplets in the gel network reduced the degree of gelation of the microgel because the diffusion rate of Ca2+ cation in the microgel is reduced. The degree of gelation of the W/O emulsion droplets encapsulated microgel is 0.6 when the diameter of the droplet is reduced to 77.5 μm and the concentration of CaCl2 solution is doubled to 22 kg m−3. The potentiality of the impinging aerosol system to produce Ca-alginate microgels to encapsulate hydrophilic compounds with improved barriers is presented in this work.

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