Mohanad Bashari

An Overview of Ultrasound-Assisted Food-Grade Nanoemulsions

Nanoemulsions are considered a very important tool for the delivery of bioactive compounds to the human body through food systems. Application of low-frequency ultrasound, a high-energy method, facilitates the homogenization and dispersion process under the influence of cavitation phenomena. Frequency, time, power, oil phase and aqueous phase are major parameters governing the cavitation process, concomitantly influencing the size and polydispersity index of nanoemulsion droplet. Additionally, hydrostatic pressure, gas content and temperature may also have profound effects on the process. Present review highlights the principles and production technology of high-intensity ultrasound and discusses the role of acoustic cavitation in the preparation of food-grade O/W nanoemulsions. Finally, it indicates technical hurdles, issues and future prospects of the technology.

Process optimization of ultrasound-assisted curcumin nanoemulsions stabilized by OSA-modified starch.

This study reports on the process optimization of ultrasound-assisted, food-grade oil-water nanoemulsions stabilized by modified starches. In this work, effects of major emulsification process variables including applied power in terms of power density and sonication time, and formulation parameters, that is, surfactant type and concentration, bioactive concentration and dispersed-phase volume fraction were investigated on the mean droplet diameter, polydispersity index and charge on the emulsion droplets. Emulsifying properties of octenyl succinic anhydride modified starches, that is, Purity Gum 2000, Hi-Cap 100 and Purity Gum Ultra, and the size stability of corresponding emulsion droplets during the 1 month storage period were also investigated. Results revealed that the smallest and more stable nanoemulsion droplets were obtained when coarse emulsions treated at 40% of applied power (power density: 1.36 W/mL) for 7 min, stabilized by 1.5% (w/v) Purity Gum Ultra. Optimum volume fraction of oil (medium chain triglycerides) and the concentration of bioactive compound (curcumin) dispersed were 0.05 and 6 mg/mL oil, respectively. These results indicated that the ultrasound-assisted emulsification could be successfully used for the preparation of starch-stabilized nanoemulsions at lower temperatures (40-45 °C) and reduced energy consumption.

Influence of low ultrasound intensity on the degradation of dextran catalyzed by dextranase

In our current research work, the effect of ultrasound irradiation on the enzymatic activity and enzymatic hydrolysis kinetic parameters of dextran catalysis by dextranase were investigated. Furthermore, the effects of ultrasound irradiation on the structure of dextranase were investigated with the aid of fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The maximum activity of dextranase was observed when the sample was treated with ultrasound at 25 kHz, 40 W for 15 min, under which the enzyme activity increased by 13.43% compared the routine thermal incubation at 50 °C. Experimental Kinetics results, demonstrated that, both the V(max) and K(M) values of dextranase increased with ultrasound-treated compared with the incubation at 50 °C. Likewise, both the catalytic and specificity constants were higher under the effects of an ultrasonic field, indicating that, the substrate is converted into the product at an increased rate when compared with the incubation at 50 °C. On the other hand, fluorescence and CD spectra reflected that the ultrasound irradiation had increased the number of tryptophan on dextranase surface with increased α-helix by 15.74% and reduced random coil by 5.41% upon ultrasound-treated dextranase protein compared to the control, which were helpful for the improvement of its activity.

Fabrication of polymeric nanocapsules from curcumin-loaded nanoemulsion templates by self-assembly.

In this study, biodegradable polymeric nanocapsules were prepared by sequential deposition of food-grade polyelectrolytes through the self-assembling process onto the oil (medium chain triglycerides) droplets enriched with curcumin (lipophilic bioactive compound). Optimum conditions were used to prepare ultrasound-assisted nanoemulsions stabilized by octenyl-succinic-anhydride (OSA)-modified starch. Negatively charged droplets (-39.4 ± 1.84 mV) of these nanoemulsions, having a diameter of 142.7 ± 0.85 nm were used as templates for the fabrication of nanocapsules. Concentrations of layer-forming cationic (chitosan) and anionic (carboxymethylcellulose) biopolymers were optimized based on the mean droplet/particle diameter (MDD/MPD), polydispersity index (PDI) and net charge on the droplets/capsules. Prepared core-shell structures or nanocapsules, having MPD of 159.85 ± 0.92 nm, were characterized by laser diffraction (DLS), ζ-potential (ZP), atomic force microscopy (AFM), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). Furthermore, physical stability of curcumin-loaded nanocapsules in suspension was determined and compared at different storage temperatures. This study may provide information regarding the formation of ultrasound-assisted polymeric nanocapsules from the nanoemulsion templates which could be helpful in the development of delivery systems for lipophilic food bioactives.

Improved stability and controlled release of ω3/ω6 polyunsaturated fatty acids by spring dextrin encapsulation

Food grade biopolymers, such as dextrin, have been suggested as a technological solution for the controlled delivery of health promoting substances. The main focus of this work is to improve the stability of poly-unsaturated fatty acids (PUFAs) and controlled release by encapsulating with helical spring dextrin (SD). The encapsulation was formed between SD with a DP¯ of 62 and α-linolenic acid (ALA) or linoleic acid (LA) at 60 °C and characterized by WXRD, DSC, TGA and SEM. Under conditions which simulated the human environment of the gastrointestinal system, 21.7% and 18.5% of SD-ALA and SD-LA were released, respectively. A molecular dynamics simulation indicated that the space of helix cavity for ALA-SD complex was larger than that for LA-SD complex. This research work supports the idea that these complexes not only can improve the stability of ALA and LA, but also can achieve the targeted delivery of functional lipids or other bioactive components to the small intestine.

Identification and releasing characteristics of high-amylose corn starch-cinnamaldehyde inclusion complex prepared using ultrasound treatment.

In this study, the high-amylose corn starch-cinnamaldehyde inclusion complex was prepared by an ultrasound treatment and its releasing characteristic was investigated. The results showed that the ultrasound treatment (35°C, 10min and 250W) generated a higher encapsulation rate of 40.2% than the conventional treatment (encapsulation rate, 5.7%). Data obtained from Fourier-transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA) indicated that cinnamaldehyde was successfully encapsulated by high-amylose corn starch and the encapsulation significantly increased the dissociation temperature of cinnamaldehyde by around 70°C. Compared to the physical mixture of high-amylose corn starch and cinnamaldehyde, the formed inclusion complex had good retention ability and reduced the releasing rate of cinnamaldehyde from 57.5% to 28.4% in the first week. These results suggest that cinnamaldehyde could be encapsulated by high-amylose corn starch with an ultrasound treatment for presenting the releasing behavior in food preservation.

Ultrasound-assisted dextranase entrapment onto Ca-alginate gel beads

In this research work, dextranase has immobilized onto calcium alginate beads using a novel ultrasound method. The process of immobilization of the enzyme was carried out in a one-step ultrasound process. Effects of ultrasound conditions on loading efficiency and immobilization yield of the enzyme onto calcium alginate beads were investigated. Furthermore, the activity of the free and immobilized enzymes prepared with and without ultrasound treatment, as a function of pH, temperature, recyclability and enzyme kinetic parameters, was compared. The maximum loading efficiency and the immobilization yield were observed when the immobilized dextranase was prepared with an ultrasonic irradiation at 25 kHz, 40 W for 15 min, under which the loading efficiency and the immobilization yield increased by 27.21% and 18.77%, respectively, compared with the immobilized enzymes prepared without ultrasonic irradiation. On the other hand, immobilized enzyme prepared with ultrasonic irradiation showed Vmax and KM value higher than that for the immobilized enzyme prepared without ultrasonic irradiation, likewise, both the catalytic and specificity constants of immobilized enzyme prepared with ultrasonic irradiation were higher than that for immobilized enzyme prepared without ultrasound, indicating that, this new ultrasonic method improved the catalytic kinetics activity of immobilized dextranase at all the reaction conditions studied. Compared with immobilized enzyme prepared without ultrasound treatment, the immobilized enzymes prepared with ultrasound irradiation exhibited: a higher pH optimum, optimal reaction temperature, activation energy, and thermal stability, as well as, a higher recyclability, which, illustrating the effectiveness of the sonochemical method. To the best of our knowledge, this is the first report on the effect of ultrasound treatments on the immobilization of dextranase.

Separation and characterization of dextran extracted from deteriorated sugarcane

In this research work, dextran was extracted from deteriorated sugarcane by alcohol precipitation and purified by gel filtration chromatography. Total acid hydrolysis and enzymatic degradation were utilized to confirm the purity of separated polysaccharide. Using the more recently available techniques such as ((1)H,(13)C) and two-dimensional (COSY and HMQC) NMR spectral analysis, methylation GC-MS and MALDI-TOF mass spectrometry, the structure of sugarcane dextran (SC-Dex) was investigated. On the basis of all spectra, SC-Dex showed a branched polysaccharide that contained only d-glucose residues in consecutive α-(1-6) linkages in the main chain with α-(1-3) branches. Methylation analysis showed that, the degree of α-(1-3) branching levels was 4.37%. Several structural fragments were identified from MALDI-TOF spectrum with peak-to-peak mass difference of 162gmol(-1), which confirmed that the repeat unit in SC-Dex was d-glucose. The surface morphology of SC-Dex, revealed the spherically shaped and porous structure. Using HPSEC-MALLS-RI system, the average molecular weight of SC-Dex was estimated to be 1.753×10(6)gmol(-1) with an index of polydispersity value of 1.069.

Effect of ultrasound and high hydrostatic pressure (US/HHP) on the degradation of dextran catalyzed by dextranase.

In our current research work, the effect of combination of ultrasonic irradiation and high hydrostatic pressure (US/HHP) on the enzymatic activity and enzymatic hydrolysis kinetic parameters of dextran catalytic by dextranase were investigated. Furthermore, the effects of US/HHP on the structure of dextranase were also discussed with the aid of fluorescence spectroscopy and circular dichroism (CD) spectroscopy. The maximum hydrolysis of dextran was observed under US (40 W at 25 kHz for 15 min) combined with HHP (400 MPa for 25 min), in which the hydrolysis of dextran increased by 163.79% compared with the routine thermal incubation at 50 °C. Results also showed that, Vmax and KM values, as well as, kcat of dextranase under US/HHP treatment were higher than that under US, HHP and thermal incubation at 50 °C, indicated that, the substrate is converted into the product at an increased rate when compared with the incubation at 50 °C. Compared to the enzymatic reaction under US, HHP, and routine thermal incubation, dextranase enzymatic reaction under US/HHP treatment showed decreases in Ea, ΔG and ΔH, however small increase in ΔS value was observed. In addition, fluorescence and CD spectra reflected that US/HHP treatment had increased the number of tryptophan on dextranase surface with increased α-helix by 19.80% and reduced random coil by 6.94% upon US/HHP-treated dextranase protein compared to the control, which were helpful for the improvement of its activity. These results indicated that, the combination of US and HHP treatments could be an effective method for improving the hydrolysis of dextran in many industrial applications including sugar manufacturing processes.

Combined of ultrasound irradiation with high hydrostatic pressure (US/HHP) as a new method to improve immobilization of dextranase onto alginate gel.

In this research work, dextranase was immobilized onto calcium alginate beads by the combination of ultrasonic irradiation and high hydrostatic pressure (US/HHP) treatments. Effects of US/HHP treatments on loading efficiency and immobilization yield of dextranase enzyme onto calcium alginate beads were investigated. Furthermore, the activities of immobilized enzymes prepared with and without US/HHP treatments and that prepared with ultrasonic irradiation (US) and high hydrostatic pressure (HHP), as a function of pH, temperature, recyclability and enzyme kinetic parameters, were compared with that for free enzyme. The maximum loading efficiency and the immobilization yield were observed when the immobilized dextranase was prepared with US (40 W at 25 kHz for 15 min) combined with HHP (400 MPa for 15 min), under which the loading efficiency and the immobilization yield increased by 88.92% and 80.86%, respectively, compared to immobilized enzymes prepared without US/HHP treatment. On the other hand, immobilized enzyme prepared with US/HHP treatment showed Vmax, KM, catalytic and specificity constants values higher than that for the immobilized enzyme prepared with HHP treatment, indicated that, this new US/HHP method improved the catalytic kinetics activity of immobilized dextranase at all the reaction conditions studied. Compared to immobilized enzyme prepared either with US or HHP, the immobilized enzymes prepared with US/HHP method exhibited a higher: pH optimum, optimal reaction temperature, thermal stability and recyclability, and lower activation energy, which, illustrating the effectiveness of the US/HHP method. These results indicated that, the combination of US and HHP treatments could be an effective method for improving the immobilization of enzymes in polymers.