Material characterisation of bioplastics: Influence of different starch sources in fish gelatin-based blends

ABSTRACTThe poor barrier and mechanical properties of biopolymer‐based food packaging can potentially be enhanced by the use of layered silicates (nanoclay) to produce nanocomposites. In this study, starch‐clay nanocomposites were synthesized by a melt extrusion method. Natural (MMT) and organically modified (I30E) montmorillonite clays were chosen for the nanocomposite preparation. The structures of the hybrids were characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Films were made through casting using granulate produced by a twin‐screw extruder. Starch/MMT composite films showed higher tensile strength and better water vapor barrier properties than films from starch/I30E composites, as well as pristine starch, due to formation of intercalated nanostructure. To find the best combinations of raw materials, the effects of clay content (0–21 wt% MMT), starch sources (corn, wheat, and potato), and amylose content (≈0, 28, 55, 70, 100%) on barrier and mechanical properties of the nanocomposite films were investigated. With increase in clay content, significantly higher (15–92%) tensile strength (TS), and lower (22–67%) water vapor permeability (WVP) were obtained. The barrier and mechanical properties of nanocomposite films did not vary significantly with different starch sources. Nanocomposite films from regular corn starch had better barrier and mechanical properties than either high amylopectin or high‐amylose‐based nanocomposite films. WVP, TS, and elongation at break (%E) of the films did not change significantly as amylose content increased beyond 50%.

Caecal pH and contents of short‐chain fatty acids (SCFA) were registered in rats fed three potential sources of resistant starch (RS); raw pea starch, raw potato starch, and an RS‐enriched preparation obtained from wheat starch by autoclaving and enzymatic incubation. Small intestinal digestibility and delivery of RS to the hind‐gut in the case of raw starches were determined by analysis of faecal starch in animals treated with antibiotics to prevent hind‐gut fermentation. RS content in the RS‐enriched preparation was determined as total starch remaining in an enzymatic gravimetric dietary fibre residue. The fermentability of RS was estimated from the faecal recovery of starch in normal animals with intact hind‐gut microflora. Approximately 35 g per 100 g and 32 g per 100 g were RS in the case of raw potato starch and the RS‐enriched preparation, respectively, versus only 1 g per 100 g in the case of raw pea starch. The caecal pH decreased with all test diets, being most significant with raw potato starch. SCFA production and faecal bulking were negligible with raw pea starch, whereas both raw potato starch and the RS‐enriched preparation significantly increased these parameters. The fermentability of RS in raw potato starch and the RS‐enriched preparation was similar, or about 60–70%. If calculated on basis of fermented amount, RS in raw potato starch was more potent in generating SCFA (49 μmol g−1) than in the RS‐enriched preparation (19 μmol g−1). RS in raw potato starch also displayed the highest faecal bulking capacity. In fact, the faecal dry weight increased more than expected merely from delivery of RS. The relative proportion in caecal contents of acetic‐, propionic‐ and butyric acid was 70, 17 and 8%, respectively, with no significant differences between the three sources of RS.

This in vitro study describes and characterizes a developed novel method to produce coatings on Ti. Hydrophobic coatings on substrates are needed in prosthetic dentistry to promote durable adhesion between luting resin cements and coated Ti surfaces. In implant dentistry the hydrophobic coatings on a Ti implant might be beneficial for osseointegration, preventing bacteria adhesion and for enhancement of resin composite adhesion as well. A silica-coating system, Rocatec™, was used for planar Ti coupons as instructed. After careful rinsing and drying, four experimental silane primers were applied onto silica-coated Ti specimens. The primers were prepared of 3-acryloxypropyltrimethoxysilane + bis-1,2-(triethoxysilyl)ethane (in four concentrations), diluted in acidified ethanol-water. The contact angles, surface free energies, and critical surface tensions were assessed. The chemical compositions of surfaces were analyzed using X-photoelectron spectroscopy. Atomic force microscopy was used to investigate the surface topographies. Non-treated Ti specimens and silanized with a commercial silane primer were used as the controls. There were observable differences in the surface free energy (contact angle) and chemical composition on specimens. The silane primers reacted and fully covered Ti surfaces, which produced more hydrophobic coatings, larger contact angles, and lower surface free energy and critical surface tension than controls. At the concentration of 1.0 vol% 3-acryloxypropyltrimethoxysilane and 0.3 vol% bis-1,2-(triethoxysilyl)ethane, the silane blend showed the lowest surface free energy. The silanes would not affect the surface roughness (P > 0.05). Novel coatings were successfully developed and optimized. They may produce a hydrophobic surface onto Ti implants without compromising the surface roughness.

Raw corn starch (RCS), raw tapioca starch (RTS), raw potato starch (RPS), pre-gelatinized corn starch (PCS), pre-gelatinized tapioca starch (PTS) and pre-gelatinized potato starch (PPS) were evaluated as starch sources in diets for yellowfin seabream Sparus latus in a 56-day growth trial. Seven isonitrogenous semi-purified diets comprising a non-starch cellulose control diet and the six different starch sources holding 200 g kg−1 starch each were prepared and fed to triplicate groups of juvenile yellowfin seabream S. latus. Fish were fed for 8 weeks. Weight gain (WG) and specific growth rate (SGR) for fish fed RCS, RTS and RPS diets were equal, as well as for fish fed PCS, PTS and PPS diets, but values in groups fed the raw starch sources were significantly higher compared with fish fed the pre-gelatinized starches. Feed efficiency and protein efficiency ratio in fish fed different starch source diets showed no significant differences but were significantly higher than those fed a non-starch control diet. Protein productive value was improved by starch incorporation to diets. PCS, PTS or PPS groups showed lower feed intake compared with RCS, RTS or RPS groups, and the differences were significant between PCS, PPS and RCS, RPS groups. Whole-body protein and ash contents and muscle compositions were not affected by different starch sources. Whole-body and liver lipid contents, liver moisture and glycogen contents were significantly affected by starch source. Values of hepatosomatic index, intraperitoneal fat ratio, viscerosomatic index and condition factor did not vary between experimental treatments. Plasma total protein concentration for RCS, RTS or RPS fed fish was significantly higher than that for PCS, PTS or PPS fed fish, but significantly lower than that for non-starch fed fish. Plasma cholesterol and triacylglycerol concentrations were unaffected by starch source, but were significantly higher in fish fed the non-starch control diets. Plasma glucose concentrations in all dietary groups were relatively stable. In conclusion, raw corn, tapioca and potato starches at a 200 g kg−1 inclusion level were well utilized as energy sources by yellowfin seabream, which was evidenced by better WG and SGR. Pre-gelatinization of the starches had no positive effect on starch utilization.

Surface free energy analysis for stable supercooling of sodium thiosulfate pentahydrate with microcosmic-visualized methods

Lowering of surface free energy of Polythiophenes through entropy control in side chains without Perfluoroalkyl groups.

The objectives of this study were to investigate the improvement on flowability of a model cohesive powder using two different types of fumed silica mixed by the dry coating method “mechanofusion” and to explore the relationship between flowability and surface free energy and/or wettability. The first aim was to find the optimum conditions for improving the flowability of a model cohesive powder, glass microspheres (DMV ~ 3.5 µm), by mechanofusion with fumed silica. Conventional blending using tumbling was done as a comparison. Mechanofusion was conducted at three different speeds 1500, 3000 and 4500 rpm and at three concentrations of hydrophobic Aerosil®R972 (1%, 3% and 5% w/w) for 10 minutes, while conventional blending was performed at 72 rpm for 30 minutes. It was revealed that the optimum concentration to improve flowability was 1% w/w Aerosil®R972 for all processes utilized. Increasing the concentration of the fumed silica decreased the flowability at all speeds. This indicates the enhancement of flowability of this model cohesive powder depends on the concentration of guest particles. The influence of different speeds to the flowability was observed upon the increasing concentration of Aerosil®R972 at 3% and 5% w/w. Mechanofusion was found to be a more effective mixing method compared to tumbling mixing presumably due to the higher energy applied that can de-agglomerate the cohesive microspheres. The second aim of this thesis was to determine the mechanism of action of the fumed silica in improving cohesive powder flow and to investigate the relationship between flowability and surface free energy and/or wettability. Hydrophilic fumed silica Cab-o-sil®M-5, which has the same particles size as Aerosil®R972, was used as a comparison. 1% w/w Cab-o-sil®M-5 failed to improve the flow of particles, whereas the same concentration of Aerosil®R972 did. Powder wettability and surface free energy were derived from contact angle measurements of uncoated and coated particles. The capillary rise technique was used to measure powder contact angles. The water contact angle increased when the glass microspheres were coated with hydrophobic Aerosil®R972, whereas it decreased when coated with hydrophilic Cab-o-sil®M-5. However, the 1-bromonaphthalene contact angle increased after coating with both types of fumed silica. The contact angle data was used to calculate the surface free energy of uncoated and coated particles. A decrease in dispersive and polar components of surface free energy was found in particles coated with hydrophobic fumed silica, while the surface free energy of particles coated with hydrophilic fumed silica reached the highest value. Particles with higher surface free energies had poorer flow than particles with lower surface free energies. Similarly, particles with a water contact angle less than 90° had lower flowability than particles with a water contact angle higher than 90°. Therefore, this study found that the improvement of flowability of micronized cohesive particles can be achieved by mechanofusion provided the chosen guest particle has relatively low surface free energy and/or is hydrophobic. The outcomes of this thesis present an enhanced better understanding of improving the flowability of a cohesive powder using fumed silica. These findings may have future value for the development of improved solid formulation of pharmaceutical preparations with the active pharmaceutical ingredients (APIs) in micron size.

The ability of low- and high-density polyethylene, polypropylene and polyvinyl chloride to wet the surface of dispersed particles of wood flour was assessed by comparing the values of the critical surface wetting tension of the polymer and filler. The critical surface tension of wood flour is determined by its dependence on the solubility parameter of the filler. It was revealed that wood flour has the highest value of critical surface tension, and thermoplastic polymers have lower values of critical surface tension. It has been shown that non-polar hydrophobic thermoplastic polymers poorly wet the hydrophilic surface of wood flour. The relationship between the parameters of solubility, polarity of the studied thermoplastics and filler and their critical surface wetting tension has been established. Moreover, the more the thermoplastics and the filler differ from each other in their polarity and solubility parameters, the greater the critical surface wetting tension at the boundary between them and the worse the wetting in this system. Wetting occurs when the critical surface tension of the filler is greater than the critical surface tension of the thermoplastic polymer at the filler-melt polymer interface. When the values of the critical surface tension of the filler and the polymer are equal, the spreading of the liquid polymer over the surface of the filler stops and the greatest adhesive strength between them is achieved. The energy and acid-base characteristics of the surface of the studied polymers and filler were determined. It was revealed that the surfaces of polyvinyl chloride, polypropylene, high-density polyethylene and wood flour have acidic properties. Low pressure polyethylene has basic properties. The results obtained, with the exception of the HDPE-wood flour pair, indicate the absence of acid-base interaction between the polymer matrix and wood flour. It has been established that in wood-polymer compositions the interaction between the polymer and the filler is weak and is determined only by intermolecular forces. The calculated values of adhesion of the studied polymers to wood flour are given. It has been shown that polyvinyl chloride has the greatest adhesion to the filler, and polypropylene has the least.

A series of cationic polyurethane-fluorinated acrylic hybrid latex (PUFA) have been synthesized by solvent-free method. In the method, vinyl monomers acted as dilution agent and the polyurethane (PU) having quaternary ammonium groups acted as macromolecular emulsifier without using any other solvent and surfactant. The structure and properties of PUFA were characterized by Fourier transform infrared spectroscopy (FT-IR), F19 nuclear magnetic resonance (F19 NMR), particle size distribution (PSD) analysis, transmission electron microscopy (TEM), contact angle (CA), surface free energy analysis, scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometry (EDS), and thermogravimetric (TG) analysis. The FT-IR, F19 NMR, and EDS confirmed that the FA monomer had been introduced into the chain of the PUFA hybrid polymer. The PSD analysis indicated the particles of PUFA were smaller than corresponding pure PU dispersion and narrower in particle size distribution. The CA and surface free energy analysis proved the PUFA hybrid latex film with fluorine possessed higher contact angle and lower surface free energy in contrast with the film without fluorine. The FPUA films exhibited good surface property which could be enhanced at higher annealing temperature. The EDS of PUFA confirmed the fluorine enrichment on the surface of PUFA. TG analysis suggested the PUFA hybrid latex film had a better thermal stability than pure PU.

The critical surface tension (CST) pointed out by Zisman is a practical parameter related to complete wetting of fibers. In the form of fiber, in general, the value of CST is estimated with some difficulties because of complex contact of fiber with liquid or unevenness of fibersIt was found that the value of CST could also be estimated, using the previously reported hydrodynamic apparatus on estimation of wettability of fiber assemblies. This study is mainely concerned with the principles and methods of determination of CST in the fiber assembly.The measurement of CST was based on the calculations of penetrating velosity (dh/dt) of dipsolution through capillaries in fiber assembly under forced flowing of dip-solution. Continious record of water pressure during the wetting process permitted the calculations of average water level in sample chamber and two curves of pressure and water level on the same time-scale permitted the comparision of amounts of pressure occured naturally in capillaries and of pressure loss due to forced flowing. The recorded pressure, when the two kinds of pressure just compensated, gave the value of dh/dt. By determination of the relation between dh/dt and water level in chamber, the product of radius of capillary by cosine of contact angle was obtained as an average value on numerous capillaries. Further, the plotting of these products vs surface tension of dip-solutions gave the value of CST of sample fibers in accordance with Zisman's method.Using above described method, value of CST of merino '64 wool fiber was determined at about 30 dyne/cm. This value was much smaller than the values reported in literatures, but it might be considered that this represented the more real value on undamaged clean wool fiber.Consequently, the merits of this hydrodynamic estimation were summarized as follows; 1) CST was determined as an average value of numerous fibers, 2) not only the CST, but the average radius of capillaries in fiber assembly could be estimated, 3) convenient determination of CST was also possible, by comparision of the shapes of pressure-time curves obtained on a series of solutions having various surface tensions.

Physicochemical and microstructural characterization of films prepared by thermal and cold gelatinization from non-conventional sources of starches

A novel starch source from water chestnut (WCS) was used to develop composite film with polyvinyl alcohol (PVA) and different plasticizer's effects on functional properties were investigated. Results showed that the plasticizer decreased the swelling capacity but conversely increased the film solubility. The tensile strength (TS) of WCS-PVA film improved when incorporating plasticizer but gradually reduced at higher plasticizer concentration. The TS reached the maximum value of 28.82 and 17.14 MPa with sorbitol and glycerol, respectively, at 20% concentration. Conversely, elongation at break was decreased first and then increased with concentration. The water vapor permeability was observed to be slightly increased from 1.698 × 10−10 to 1.744 × 10−10 g Pa−1 m−1 s−1 for G-plasticized films and 1.124 × 10−10 to 1.134 × 10−10 g Pa−1 m−1 s−1 for S-plasticized films. Also, the result indicated that the incorporation of plasticizers enhanced biodegradability and made them suitable for food packaging without any hazardous effects. Novelty impact statement In previous work, starch-based films with polyvinyl alcohol (PVA) were prepared from different starch sources. However, no study has been reported so far on biocomposite film made from water chestnut with PVA. This paper was reported for the first time for the development of WCS-PVA biocomposite film and demonstrated the different plasticizer effects on its physical, barrier, and mechanical properties.

Mechanical and water barrier properties of isolated soy protein composite edible films as affected by carvacrol and cinnamaldehyde micro and nanoemulsions

As an emerging droplet system, monolayer nanoparticle‐covered (mNPc) liquid marbles have shown fascinating properties and application values. Their formation process has been clear, but liquid availability for production has yet to be clarified. This study addresses this issue from the angle of surface tension, revealing critical surface tension and contact angle values for mNPc liquid marble production with both rolling and compression methods. Water‐ethanol and water‐surfactant systems are employed as testing liquids. With irreversible pinning as criterion, critical surface tension values that allow mNPc liquid marble formation are obtained with the two kinds of liquids, forming ranges from 38.6 to 31.8 mN m−1, and from 36.7 to 27.6 mN m−1, for the rolling and compression methods, respectively. Correspondingly, contact angles in the ranges from 132° to 126° and from 116–124° are regarded as the lower limits for mNPc liquid marble production with the rolling and compression methods, respectively. In addition, rupture and deformation behaviors under low surface tension are systematically investigated and a depinning approach that facilitates marble formation is proposed. This study could provide important guidance for various applications that require low surface tension liquids to produce mNPc liquid marbles.

Silicone-containing polymer matrices as protective coatings: Properties and applications