Increasing Glycerol Concentration Research Articles

Properties of Edible Films Made From Anchovy By-Product Proteins and Determination of Optimum Protein and Glycerol Concentration by the TOPSIS Method

ABSTRACTIn the present study, the physicochemical and mechanical properties of films made from anchovy (Engraulis encrasicholus) by-product proteins (ABPs) were characterized as a function of protein (3, 4, and 5%) and glycerol (30, 40, 50, and 60%) concentration. In particular, the thickness, color, transparency, water vapor permeability (WVP), solubility, oxygen permeability (OP), and mechanical properties of the films were measured, and generally, these properties were affected by both protein and glycerol concentration. The thickness, redness, WVP and solubility values of films increased, while their lightness and yellowness values decreased as protein concentration increased. Furthermore, lightness, yellowness, and elongation at break (EAB) values were found to increase at higher glycerol concentrations within ABP films, whereas tensile strength (TS) and elastic modulus (EM) values decreased. ABP films became more transparent with increase of glycerol concentration and decrease of protein concentration. The OP values of all films decreased depending on protein and glycerol concentration. The techniques for order performance by similarity to ideal solution (TOPSIS) method was used to determine optimum protein and glycerol concentrations. According to this method, an edible film containing 4% protein and 40% glycerol was the best film with a C value of 0.6665.

Electrochemical signature of hen egg white lysozyme at the glycerol-modified liquid-liquid interface

Electrochemical characterization of hen egg white lysozyme (HEWL) at a glycerol-modified interface between two immiscible electrolyte solutions (ITIES) was conducted using a microporous silicon membrane-supported gelled-1,6-dichlorohexane|water-glycerol interface. The electrochemical response of HEWL under these conditions is of interest for the system’s potential application to the formation of isorefractive emulsified-ITIES, which offer practical opportunities for spectrophotometric analysis of interfacial processes. Importantly, the voltammetric signature for HEWL seen under glycerol-rich conditions was similar but with some differences from that for glycerol-free conditions. Specifically, the potential at which facilitated transfer of the organic phase electrolyte anion tetrakis-(4-chlorophenyl) borate (TPBCl−) occurred was shifted to lower potential with increasing glycerol concentration. However, features in the voltammetry associated with adsorption/desorption processes were observed to remain constant. The simple ion transfer response of tetraethylammonium cations (TEA+) at the same glycerol-modified ITIES provides insight into the nature of changes that determine the atypical HEWL signature. Lower ion transfer current with respect to increasing glycerol concentration and a shift in transfer potential were the key findings here. The results indicate that the electrochemistry which determines the HEWL signature is similar in environments that are rich in glycerol or purely aqueous.

Study of combined effects of glycerol and transglutaminase on properties of gelatin films

Gelatin films plasticized with different glycerol contents (0–40%) were cross-linked using transglutaminase (TGase). Unmodified films were prepared as controls. Cross-linking degree of the films decreased linearly with increasing glycerol content, resulting in an increase in water solubility. Glycerol increased the mobility and free volume of the gelatin film matrix as observed by differential scanning calorimetry, thus increasing the moisture content and thickness. Tensile strength and Young's modulus had a negative linear correlation with glycerol content, with no significant differences between TGase-modified and unmodified films (p > 0.05). However, TGase-modified films showed a 294% and 187% relative increase in elongation at break and toughness, respectively, in comparison with controls at 30% glycerol content (p < 0.05). X-ray diffraction and circular dichroism spectroscopy both showed a linear decrease in triple-helix content as glycerol content increased, and TGase-modified films had lower triple-helix contents. Also, the second derivative of FTIR spectra showed that TGase-modified films had increased single α-helix structures, but decreased disordered coil structures. In addition, SEM results indicated that TGase-modified films had more smooth and compact microstructures, especially at high glycerol contents (30–40%).

An experimental study of rheological properties and stability characteristics of biochar-glycerol-water slurry fuels

The rheological behaviour and stability characteristics of biochar-glycerol-water slurry fuels were experimentally investigated, emphasising the effect of glycerol addition. A pine sawdust biochar with a size fraction of <32μm and a median particle size (D50) of approximately 12μm was used. A biochar-glycerol-water slurry fuel was prepared by dispersing biochar particles in a premixed glycerol/water solution as the suspending medium with glycerol content varying from 0 to 100wt%. 2wt% lignosulfonic acid sodium salt (LASS) (on the basis of dry weight of biochar) was added to the suspending medium as a dispersant. The effect of glycerol content on the rheological properties and stability characteristics of the slurry fuels were studied. The yield stress was measured with a Brookfield vane viscometer and the dependence of apparent viscosity and shear stress on the shear rate was characterised using a Haake VT550 cone and plate viscometer. The stability characteristics of the slurry fuels were characterised by using a “drop rod” method. As glycerol content increased, the maximum biochar loading decreased from 50 to 10wt% while the calorific values of the slurry fuels first increased and then decreased, reaching a maximum of 21MJkg−1 at 90wt% glycerol content. For a given biochar loading, increasing glycerol content increased the viscosity of the suspending medium and therefore the viscosity of the slurry fuels, displaying higher yield stress, more apparent shear-thinning behaviour and higher stability due to the enhanced flocculation of biochar particles.

Elucidating the Effect of Glycerol Concentration and C/N Ratio on Lipid Production Using Yarrowia lipolytica SKY7

The high demand for renewable energy and increased biodiesel production lead to the surplus availability of crude glycerol. Due to the above reason, the bio-based value addition of crude glycerol into various bioproducts is investigated; among them, microbial lipids are attractive. The present study was dedicated to find the optimal glycerol concentration and carbon/nitrogen (C/N) ratio to produce maximum lipid using Yarrowia lipolytica SKY7. The glycerol concentration (34.4 to168.2g/L) and C/N ratio (25 to 150) were selected to investigate to maximize the lipid production. Initial glycerol concentration 112.5g/L, C/N molar ratio of 100, and with 5%v/v inoculum supplementation were found to be optimum for biomass and lipid production. Based on the above optimal parameters, lipid concentration of 43.8%w/w with a biomass concentration of 14.8g/L was achieved. In the case of glycerol concentration, the maximum Yp/s (0.192g/g); Yx/s (0.43g/g) was noted when the initial glycerol concentration was 112.5g/L with C/N molar ratio 100 and inoculum volume 5%v/v. The glycerol uptake was also noted to increase with the increase in glycerol concentration. At low C/N ratio, the glycerol consumption was found to be high (79.43g/L on C/N 25) whereas the glycerol consumption was observed to decrease when the C/N ratio was raised to 150 (40.8g/L).

Correlation and measurement of density and viscosity of aqueous mixtures of glycerol and N-methyldiethanolamine, monoethanolamine, piperazine and ionic liquid

The density and viscosity of aqueous mixtures of glycerol and N-Methyldiethanolamine (MDEA), glycerol and Monoethanolamine (MEA), glycerol and Piperazine (PZ) as well as glycerol and ionic liquid (IL) 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]) were determined in this study. It was found that the density and viscosity of the mixtures increased with increasing glycerol concentration. The correlations of density and viscosity of the mixtures were determined as a function of the concentration of glycerol and temperature. For density correlation, the empirical linear equation used in this work showed excellent accuracy with 0.62% as the highest percentage deviation for all the mixtures involved. While for the viscosity correlation, there was a good fit between the mixtures and the extended Arrhenius equation with 9.91% as the highest percentage deviation from the experimental viscosity data.

Anaerobic Degradation of Pure Glycerol for Electricity Generation using a MFC: The Effect of Substrate Concentration

Alternative glycerol treatment and valorization, could be a promising solution, contributing to the biodiesel production economy. Thus, the potential of electricity generation from pure glycerol, using a two-chamber microbial fuel cell (MFC), was evaluated. The effect of glycerol concentration in a range of 0.5–5.2 g COD L−1 on MFC performance was examined. In order to achieve a stable MFC performance and a high power density, special attention was paid during the acclimation phase of the anaerobic consortium, which was performed using glucose, instead of glycerol, as substrate. The best performance of the cell was observed at a glycerol concentration of 3.2 g COD L−1. At this concentration, the Coulombic efficiency (CE) was 34.1 %, the chemical oxygen demand (COD) removal efficiency was approximately 99 % and the maximum power density was 65.4 mW m−2. Further increase of glycerol concentration to 5.2 g COD L−1 did not enhance the MFC performance, since the power density remained at 63.4 mW m−2, while the CE and the COD removal efficiency decreased to 22.1 and 81 %, respectively. The experimental results showed that glycerol is a suitable and promising substrate for power generation, using a simple two-chamber MFC and that acclimation of anaerobic sludge using glucose as substrate, is a suitable procedure for securing a stable MFC performance, even at high glycerol concentrations.

Physicochemical characteristics of glycerol‐plasticized dextran/soy protein isolate composite membranes

ABSTRACTThis work deals with the preparation and characterization of in situ crosslinked dextran/soy protein isolate composite membranes as a function of increasing glycerol content. The surface morphology of the membranes, as evidenced from field emission scanning electron microscopy and atomic force microscopy, exhibited smoother surfaces with increasing glycerol content up to 30%. The wettability, color, and UV‐blocking characteristics of the membranes were studied. The glycerol content also significantly influenced the water vapor transmission rate of the membranes, demonstrating diminishing membrane permeability with increasing glycerol content. In addition, the membranes presented an increase in water vapor loss up to 5 h with glycerol content ranging from 10% to 30%, whereas a decrease in vapor loss has been elucidated with 40% glycerol. The influence of plasticization on the rheological properties of the composite fluid was investigated. Although the tensile strength and modulus decreased with increasing glycerol content up to 30%, a significant increase was observed beyond this due to the antiplasticizing effect of glycerol that is dominant at concentrations higher than 30%. A structural analysis of the membranes using attenuated total reflectance indicates an increase in the intensity of the OH stretching region with increasing glycerol content. Further, X‐ray diffraction patterns showed a decrease in crystalline behavior up to 30% glycerol content, above which the antiplasticizing effect of glycerol was dominant. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43847.

Water/glycerol mixed solvent transportation behavior of mechanically constrained agarose gels

The effect of glycerol on the solvent transportation behavior of mechanically constrained agarose gels was studied. The sample hydrogels were prepared using a water/glycerol mixed solvent containing various concentrations of glycerol. The compression load relaxed under the compression, and the volume of the agarose gels decreased synchronously with mechanical relaxation. This implied that the solvent is squeezed out due to mechanical constraints; the time constants for both the mechanical relaxation and the volume change are directly related to the friction between the solvent and the gel network structure. Both time constants increased with an increase in glycerol concentration. These results indicate that glycerol changes the gel network structure, and this is confirmed by other experimental evidence. The compression fracture stress and strain improved with an increase in glycerol content. Moreover, scanning electron microscope images showed that the mesh size of the gel network decreased with an increase in glycerol content.

Membrane lipids and cytosol carbohydrates in Aspergillus niger under osmotic, oxidative, and cold impact

The composition of the membrane lipids and cytosol soluble carbohydrates under three kinds of unfavorable impacts (osmotic, oxidative, and cold) was studied. Changes in the composition of the membrane lipids, specifically, increasing content of phosphatidic acids and decreasing levels of phosphatidylcholines and phosphatidylethanolamines, were the general response to the impacts. The degree of fatty acid unsaturation increased in all dominant phospholipids under osmotic shock, only in cardiolipins and phosphatidic acids under oxidative stress, and only in phosphatidylcholines under cold shock. Increased sterol content was observed only under cold and osmotic treatments. No general pattern was revealed in the composition of cytosol carbohydrates in response to stresses. Oxidative stress had almost no effect on the carbohydrate composition, while osmotic and cold treatments resulted in increased glycerol content and decreased total carbohydrate content. The mechanisms of fungal response to various stress impacts are discussed.

Photophysical Properties of Synthetic Food Dyes

The photophysical properties of generally-recognized-as-safe (GRAS) food dyes, such as Allura Red (AR), Tartrazine (TR), Sunset Yellow (SY) and Fast Green (FG), have rarely been reported. All these dyes exhibit very weak emission in common fluid solvents, which can explain the limited information on their photophysical properties. A significant enhancement of fluorescence emission is observed in highly viscous solvents (glycerol, etc.) and structured systems (e.g., amorphous solids, fat crystal networks, etc.). This observation has supported the hypothesis that these dyes exhibit molecular rotor behavior enabling their use as probes of microviscosity. To enhance the applicability of these potential luminescent probes, detailed information on their photophysical properties was gathered in this study. Their excitation and emission spectra were collected and Stokes shifts analyzed in a series of solvents of different polarity. Additionally, fluorescence quantum yields and lifetimes of all the dyes were determined in water:glycerol mixtures (0-98% glycerol). TR exhibited the largest Stokes shift (Δν = 5000 cm-1), followed by AR and SY (Δν = 2500 cm-1) and finally FG (Δν = 700 cm-1). The effect of environmental polarity on the fluorescence emission peak location was more pronounced for AR than for the rest of the probes. For dyes in water at 296K, the fluorescence quantum yields (Q) and lifetimes (τ) were extremely small (0.0001-0.0005 and 10-20 ps, respectively). However, for all dyes, a significant increase in Q and τ was observed by increasing medium viscosity at fixed temperature (increasing glycerol content in water:glycerol mixtures), by reducing the temperature to 77K, or by a combination of both, reaching values as high as Q = 0.41 and τ = 3.37 ns for FG in glycerol at 77K.This study makes a significant contribution to the currently incomplete photophysical characterization of these edible and safe-to-ingest fluorophores.

The effect of poly(glycerol sebacate) stoichiometry on its physical characteristics

Event Abstract Back to Event The effect of poly(glycerol sebacate) stoichiometry on its physical characteristics Brendan Nicholson1, Jeremy J. Harris1 and Julia Donnelly1 1 Secant Medical, Inc., United States Introduction: Poly(glycerol sebacate) (PGS) has gained much attention in the area of regenerative medicine and the majority of studies have focused on the polymer synthesized from an equimolar ratio of sebacic acid to glycerol. However, unequal stoichiometric ratios could produce polymers that have advantageous chemical and physical properties. Based on our analysis of PGS synthesized from varying monomer stoichiometries, we hypothesize that the physical properties of the resultant PGS will be tunable to allow for applications to a wider range of tissue engineering applications. Materials and Methods: All PGS was synthesized via a polycondensation reaction between glycerol and sebacic acid. Reactors were charged with variable molar ratios of glycerol to one molar equivalent of sebacic acid and 3 molar equivalents of water. The ratios of glycerol to sebacic acid were 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, and 1.3. The reactors were heated to 140°C under flow of N2 and stirred until the sebacic acid was melted. The temperature was then set to 120°C and held under N2 flow for 24 hours, then 130°C and under vacuum (~10 Torr) for 26 hours. The resultant resins were characterized by gel permeation chromatography (GPC), residual acid value titration, and oscillatory rheometry. Results and Discussion: GPC chromatograms (Fig. 1) of the PGS resins show a trend of decreasing Mw and Mw/Mn values with increasing glycerol:sebacic acid ratio. This indicates that the polymer chains self-terminate in excess glycerol, leading to a higher concentration of low Mw polymers. This is confirmed by the residual acid value titration showing a trend of decreasing residual acid with increasing glycerol content. Oscillatory rheometry amplitude sweeps (Fig. 2) performed at 25°C show increasing storage (G') and loss (G") moduli with increasing glycerol ratio. At ratios above 0.8, G' dominates G" resulting in an elastic solid. The yield strain of the polymer also increases with increasing glycerol, indicating that the elasticity of the polymer is increasing. Conclusions: Polymerization of PGS with varied monomer stoichiometric ratios results in a change of the physical characteristics of the resulting polymer. Acid values, Mw, and elasticity decreased and stiffness increased with increasing glycerol:sebacic acid ratios. PGS synthesized with equimolar glycerol:sebacic acid ratio exhibits a fixed relationship between Mw, acid value, and mechanical properties. Adjusting the glycerol:sebacic acid ratio shows the possibility to tune the molecular weight and mechanical properties of the polymer independently of the acid functionality. In addition to controlling the Mw of PGS, the functional group concentration (acid number) can also be tuned to allow for varying concentrations of additives to be covalently bound to the polymer matrix. This can have a broad impact on the tunability of PGS through changes in Mw, elasticity, degradation, and release kinetics of loaded drugs for various tissue engineering applications. Keywords: Functionalization, material design, Biodegradable material, Polymeric material Conference: 10th World Biomaterials Congress, Montréal, Canada, 17 May - 22 May, 2016. Presentation Type: Poster Topic: Biodegradable polymers Citation: Nicholson B, Harris JJ and Donnelly J (2016). The effect of poly(glycerol sebacate) stoichiometry on its physical characteristics. Front. Bioeng. Biotechnol. Conference Abstract: 10th World Biomaterials Congress. doi: 10.3389/conf.FBIOE.2016.01.00096 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 27 Mar 2016; Published Online: 30 Mar 2016. Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Brendan Nicholson Jeremy J Harris Julia Donnelly Google Brendan Nicholson Jeremy J Harris Julia Donnelly Google Scholar Brendan Nicholson Jeremy J Harris Julia Donnelly PubMed Brendan Nicholson Jeremy J Harris Julia Donnelly Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Preparation and properties of arenga starch-chitosan based edible film

The main objective of this research was to prepare for edible film on the basis of arenga starch-chitosan. Carboxymethyl cellulose (CMC) was added to the blend and glycerol was used as a plasticizer. The tensile strength and water uptake of the film decreased with the increasing of glycerol content in the blend. Contrary, increasing glycerol content in the blend enhanced the elongation and swelling area of the film. The film C1, which has 6% of glycerol in the blend has a tensile strength of 124 KPa, elongation of 6.55%, swelling area of 21% and water uptake of 48%. The film C2, which has 10% of glycerol in the blend has a tensile strength of 58 KPa, elongation of 8.35%, swelling area of 32% and water uptake of 5%.

Adaptation of acidogenic sludge to increasing glycerol concentrations for biohydrogen production.

Hydrogen is a promising alternative as an energetic carrier and its production by dark fermentation from wastewater has been recently proposed, with special attention to crude glycerol as potential substrate. In this study, two different feeding strategies were evaluated for replacing the glucose substrate by glycerol substrate: a one-step strategy (glucose was replaced abruptly by glycerol) and a step-by-step strategy (progressive decrease of glucose concentration and increase of glycerol concentration from 0 to 5 g L(-1)), in a continuous stirred tank reactor (12 h of hydraulic retention time (HRT), pH 5.5, 35 °C). While the one-step strategy led to biomass washout and unsuccessful H2 production, the step-by-step strategy was efficient for biomass adaptation, reaching acceptable hydrogen yields (0.4 ± 0.1 molH2 mol(-1) glycerol consumed) around 33 % of the theoretical yield independently of the glycerol concentration. Microbial community structure was investigated by single-strand conformation polymorphism (SSCP) and denaturing gradient gel electrophoresis (DGGE) fingerprinting techniques, targeting either the total community (16S ribosomal RNA (rRNA) gene) or the functional Clostridium population involved in H2 production (hydA gene), as well as by 454 pyrosequencing of the total community. Multivariate analysis of fingerprinting and pyrosequencing results revealed the influence of the feeding strategy on the bacterial community structure and suggested the progressive structural adaptation of the community to increasing glycerol concentrations, through the emergence and selection of specific species, highly correlated to environmental parameters. Particularly, this work highlighted an interesting shift of dominant community members (putatively responsible of hydrogen production in the continuous stirred tank reactor (CSTR)) according to the gradient of glycerol proportion in the feed, from the family Veillonellaceae to the genera Prevotella and Clostridium sp., putatively responsible of hydrogen production in the CSTR.

Effect of cellulose nanofibers concentration on mechanical, optical, and barrier properties of gelatin-based edible films

The effect of gelatin, glycerol, and cellulose nanofiber (CNFs) concentrations on the mechanical properties, water vapor permeability, and color parameters of films was evaluated. The results indicate that the color is only affected by the gelatin concentration. Mechanical tests indicated that with increasing concentration of gelatin and CNFs, there is an increase in tensile strength, whereas an increase in glycerol concentration causes an increase in elongation, making the films more flexible. An increased concentration of gelatin and glycerol makes the film more permeable to water vapor, while an increase in the concentration of CNFs reduces this property. Finally, the addition of CNFs to gelatin-based films improves their mechanical and barrier properties (water vapor) without affecting the appearance (color) of the films.

Kinetic Investigations of Glycerol Oxidation Reaction on Ni/C

This study evaluates the electrochemical oxidation of glycerol using a nickel-supported catalyst under several well-defined experimental conditions. The influence of scan rate, temperature, glycerol, and NaOH concentrations were systematically investigated. The slope of the log-log relationship of the anodic peak current for glycerol oxidation as a function of the scan rate indicates that the electrochemical glycerol oxidation is a complex mechanism partially limited by diffusion-controlled process. This is in agreement with the temperature effect on glycerol oxidation, since the slope value associated with the relationship between the logarithm of the current density of the anodic peak and the inverse of temperature also indicates a diffusion process. When the glycerol concentration increases, the peak associated to its oxidation also increases, but it seems to reach a limit. This behavior was associated with two main effects, i.e., the saturation of the active catalytic sites on the electrode surface and the change in the glycerol oxidation mechanism as demonstrated by FTIR spectroscopic measurements.

Bubble Formation Modeling During Laser Direct Writing of Glycerol Solutions

Laser direct writing, a noncontact modified laser-induced forward transfer (LIFT) technique, has emerged as a promising technology for various applications from microelectronics printing to biofabrication. For it to be a viable technology, the bubble formation process during laser direct writing should be carefully examined. In this study, the bubble formation process during the laser direct writing of glycerol–water solutions has been studied using a nucleation-based phase explosion modeling approach. The effects of laser fluence and material properties of glycerol solution on the resulting bubble geometry have been examined both analytically and experimentally. Overall, a satisfactory modeling accuracy has been achieved, while the proposed modeling approach slightly underestimates the bubble diameter. Both the measured and predicted bubble diameters increase when the laser fluence increases. Interestingly, the measured and predicted diameters first decrease, then increase, and decrease again with the increase of glycerol concentration. Furthermore, it is noted that the bubble diameter is more sensitive to the laser fluence than the glycerol concentration.

Oenological consequences of sequential inoculation with non-Saccharomyces yeasts (Torulaspora delbrueckii or Metschnikowia pulcherrima) and Saccharomyces cerevisiae in base wine for sparkling wine production

The use of non-Saccharomyces yeasts for the production of quality wine has become increasingly frequent in recent years. Several studies of the influence of Torulaspora delbrueckii and Metschnikowia pulcherrima on chemical composition have been reported, especially in aspects concerning aroma. The aim of this article was to study the influence of sequential inoculation of these non-Saccharomyces yeasts and Saccharomyces cerevisiae on the composition and quality of base wine for sparkling wine production. The results indicate that sequential inoculation with non-Saccharomyces yeasts may be an interesting tool for obtaining base wines with different characteristics. On the one hand, T. delbrueckii Biodiva™ strain increased glycerol concentration, reduced volatile acidity and exerted a positive effect on foaming properties improving foamability (Hm) and foam persistence (Hs). On the other hand, M. pulcherrima Flavia® strain also increased foam persistence (Hs) and changed the aromatic profile, increasing smoky and flowery notes.

Effect of glycerol and Ca+2 addition on physicochemical properties of edible carrageenan/porphyran-based films obtained from the red alga, Pyropia columbina

Our aim was to study the effect of glycerol and Ca+2 addition on physicochemical properties of phycocolloid (carrageenans/porphyrans)-based films obtained from Pyropia columbina aqueous fraction. Films were formed by casting from aqueous dispersions of phycocolloid-enriched fraction (P) with different levels of glycerol (0, 12.5, and 25 g (100 g)−1 dry solid) and the optional addition of Ca+2 (16 g (100 g)−1 dry solid), yielding six formulations according to a multi-factorial design (P, PG1, PG2, PCa, PCaG1, and PCaG2). All films were homogeneous, flexible, and slightly greenish. Moisture content, water solubility, and water vapor permeability of films were significantly increased by adding glycerol to the formulation (11, 12, and 6 %). Increasing glycerol content in formulations (12.5 to 25 g (100 g)−1 dry solid) allows obtaining more stretchable but less resistant films (with less tensile strength and elastic modulus) than those produced without plasticizer (P). Ca+2 addition masked glycerol effect in some properties (water solubility and water vapor permeability), but in others, the effect of Ca+2 was added to the plasticizer glycerol effect (mechanical properties). Ca+2 could stabilize the three-dimensional structure of P phycocolloids by interactions between sulfate groups, promote water retention, and open film structure. Use of these additives yielded films from P. columbina with a wide range of mechanical properties, thus extending the scope of these materials.

Nebulization of water/glycerol droplets generated by ZnO/Si surface acoustic wave devices

Efficient nebulization of liquid sessile droplets (water and water/glycerol mixtures) was investigated using standing waves generated using ZnO/Si surface acoustic wave (SAW) devices under different RF powers, frequencies and liquid viscosity (varied glycol concentrations in water). At such high RF powers, there are strong competitions between vertical jetting and nebulization. At lower SAW frequencies of 12.3 and 23.37 MHz, significant capillary waves and large satellite droplets were generated before nebulization could be observed. At frequencies between 23.37 and 37.2 MHz, spreading, displacement or occasionally jetting of the parent sessile droplet was frequently observed before a significant nebulization occurred. When the SAW frequencies were increased from 44.44 to 63.3 MHz, the minimum RF power to initiate droplet nebulization was found to increase significantly, and jetting of the parent droplet before nebulization became significant, although the average size of the nebulized particles and ejected satellite droplets appeared to decrease with an increase in frequency. With the increase of glycerol concentration in the test sessile droplets (or increase in liquid viscosity), nebulization became difficult due to the increased SAW damping rate inside the liquid. Acoustic heating effects were characterized to be insignificant and did not show apparent contributions to the nebulization process due to silicon substrate’s natural effect as an effective heat sink and the employment of a metallic holder beneath the ZnO/Si SAW device substrates.