Effect of chitosan on Bacillus cereus inhibition and quality of cooked rice during storage

Improper cooling of cooked rice at an inappropriate temperature or leaving cooked rice at room temperature can cause food poisoning attributed to Bacillus cereus. Natural food preservative of either squid or crab polymer chitosan solution was added to examine their antibacterial properties against Bacillus cereus in cooked rice during storage at 37 and 4 °C. Both types of chitosan could retard the growth of B. cereus and total aerobic counts in cooked rice stored at 37 °C up to 1 day. In addition, the effect of chitosans on the physical and textural properties of cooked rice during storage was studied. Both chitosans slightly increased the moisture content of cooked rice. However, chitosans had no effect on the whiteness and hardness of cooked rice during storage (P > 0.05). Therefore, both chitosans have a potential to be used as food preservative for cooked rice with no negative effects on rice quality.     

The development of injectable gelatin/silk fibroin microspheres for the dual delivery of curcumin and piperine

The objective of this study was to develop the microspheres from gelatin (G) and silk fibroin (SF) aimed to be applied for the controlled release of curcumin and piperine. The glutaraldehyde-crosslinked G/SF microspheres at various weight blending ratios (100/0, 70/30, 50/50, and 30/70) were successfully fabricated by water in oil emulsion technique. The microspheres prepared from all compositions were in a round shape with homogeneous size distribution both in the dried (194–217 μm) and swollen states (297–367 μm). When subjected in collagenase solution at physiological condition, the G microspheres gradually degraded within 14 days while the blended G/SF microspheres, particularly at 50/50 and 30/70, were not degraded. For the release application, the microspheres were loaded with curcumin and/or piperine. It was found that the microspheres composed of SF tended to entrap curcumin and piperine with the high entrapment and loading efficiencies, possibly due to their hydrophobic interactions. The G/SF microspheres, particularly at the ratios of 50/50 and 30/70, released curcumin and piperine in a sustained manner both for the single and dual release systems. The controlled dual release of curcumin and piperine from the G/SF microspheres would prolong their half-life, provide the optimal concentrations for therapeutic effects at a target site, and improve the bioavailability of curcumin. These novel injectable microspheres dually releasing curcumin and piperine would be introduced for the treatment of diseases without the need of operation.     

Gelation Process and Physicochemical Properties of Thai Silk Fibroin Hydrogels Induced by Various Anionic Surfactants for Controlled Release of Curcumin

Hydrogels based on Thai silk fibroin (SF) were prepared by the induction of various anionic surfactants including sodium octyl sulfate (SOS), sodium dodecyl sulfate (SDS), and sodium tetradecyl sulfate (STS), which have a similar chemical structure but different alkyl chain lengths and charges. The effects of anionic surfactant types and their concentrations on the gelation mechanism and time of SF were systematically investigated. We found that SDS and STS that have long alkyl chain lengths and high negative charges could accelerate the gelation of SF to occur within 14–42 min in a concentration-dependent manner. SOS that has a short alkyl chain length and low negative charge slowly induced SF to gel at around 113–144 h. The mechanisms of SF gelation induced by these three anionic surfactants were supposed to be combination of hydrophobic and electrostatic interactions, as well as the self-transition of beta sheets. The SF + STS hydrogels were further employed to encapsulate curcumin for the controlled release application. The SF + 0.09% wt. STS hydrogel encapsulating curcumin showed a slow rate of degradation while sustained the release of curcumin. This hydrogel can be applied as a minimal invasive injectable hydrogel or as a hydrogel for topical treatment of diseases.     

Green synthesis of silk sericin-capped silver nanoparticles and their potent anti-bacterial activity

In this study, a ‘green chemistry’ approach was introduced to synthesize silk sericin (SS)-capped silver nanoparticles (AgNPs) under an alkaline condition (pH 11) using SS as a reducing and stabilizing agent instead of toxic chemicals. The SS-capped AgNPs were successfully synthesized at various concentrations of SS and AgNO₃, but the yields were different. A higher yield of SS-capped AgNPs was obtained when the concentrations of SS and AgNO₃ were increased. The SS-capped AgNPs showed a round shape and uniform size with diameter at around 48 to 117 nm. The Fourier transform infrared (FT-IR) spectroscopy result proved that the carboxylate groups obtained from alkaline degradation of SS would be a reducing agent for the generation of AgNPs while COO⁻ and NH₂ ⁺ groups stabilized the AgNPs and prevented their precipitation or aggregation. Furthermore, the SS-capped AgNPs showed potent anti-bacterial activity against various gram-positive bacteria (minimal inhibitory concentration (MIC) 0.008 mM) and gram-negative bacteria (MIC ranging from 0.001 to 0.004 mM). Therefore, the SS-capped AgNPs would be a safe candidate for anti-bacterial applications.     

Hertzian-Crack Suppression in Ceramics with Elastic-Modulus-Graded Surfaces

Hertzian (spherical) indentation experiments were carried out in a graded alumina-glass composite whose Young's modulus increased with depth beneath the indented surface. An in situ processing method involving impregnation of a dense, fine-grained alumina by an aluminosilicate glass was employed to fabricate such a composite. With this technique, a monotonic, unidirectional variation in Young's modulus of as much as 50% was introduced over a distance of approximately 2 mm, while keeping the coefficient of thermal expansion and the Poisson ratio for the glass and the alumina nearly the same. The macroscopically graded, elastic composite so produced with nearly full density has essentially no macroscopic, long-range residual stresses following processing. The unidirectional variation in Young's modulus under the indenter is shown to fully suppress the formation of Hertzian cone cracks. Without these elastic-modulus gradients, cone-crack formation was observed in bulk glass and alumina. Finite-element analyses of spherical indentation on elastically graded substrates were also performed to develop a quantitative understanding of the experimental trends. It is reasoned that the present innovations, involving functionally graded surfaces and their in situ processing, provide new possibilities for enhancing certain contact-damage resistance characteristics in various ceramic materials for a broad range of engineering applications. Furthermore, this contact-damage-resistance phenomenon in functionally graded ceramics is elastic in nature, and is, therefore, likely to be immune to mechanical fatigue within the elastic limit.     

Beads fabricated from alginate,hyaluronic acid,and gelatin using ionic crosslinking and layer-by-layer coating techniques for controlled release of gentamicin

The alginate/hyaluronic acid (AL/HA) blended beads at different ratios (AL70HA30, AL50HA50, and AL30HA70) were formed by ionic crosslinking technique. The layer-by-layer coating of the beads with two opposite charged molecules, positive-charged type A gelatin (GA), and negative-charged AL, using alternate soaking technique was introduced to stabilize the beads. The AL70HA30, AL50HA50 beads showed high stability because of high ionic crosslinked AL component. Two-layer coating resulted in an appropriate layer that maximized the stability of the AL/HA beads. The higher ratio of HA resulted in the higher water absorption ability but degradation rate was accelerated. An antibiotic gentamicin was loaded into the beads with the entrapment efficiency of 69–89%. The beads containing 30% and 50% HA and coated with two layers showed a sustained release of gentamicin while the release behavior was governed by the diffusion and degradation of the beads. The gentamicin released from all beads also potentially inhibited the growth of Staphylococcus aureus (gram-positive) and Escherichia coli (gram-negative) bacteria up to at least 48 h. These beads with antibacterial activity can be further explored for the application as bone void filling material for treatment of infection in bone diseases such as osteoarthritis or rheumatoid. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46893.     

Mechanistic study on spraying of blended biodiesel using phase Doppler anemometry

Droplet size and dynamics of blended palm oil-based fatty acid methyl ester (FAME) and diesel oil spray were mechanistically investigated using a phase Doppler anemometry. A two-fluid atomizer was applied for dispersing viscous blends of blended biodiesel oil with designated flow rates. It was experimentally found that the atomizer could generate a spray with large droplets with Sauter mean diameters of ca. 30 μm at low air injection pressure. Such large droplets traveled with a low velocity along their trajectory after emerging from the nozzle tip. The viscosity of blended biodiesel could significantly affect the atomizing process, resulting in the controlled droplet size distribution. Blended biodiesel with a certain fraction of palm oil-based FAME would be consistently atomized owing to its low viscosity. However, the viscosity could exert only a small effect on the droplet velocity profile with the air injection pressure higher than 0.2 MPa.     

Chemical compositions,functional properties,and microstructure of defatted macadamia flours

The objective of this research was to study the chemical compositions, functional properties, and microstructure of partially defatted flours (PDF, 12–15% fat, dry basis (db)) and totally defatted flours (TDF, 1% db fat) from three macadamia cultivars, PY 741, DS 344, and DS 800, grown in Northern Thailand. The defatted flours were high in protein (30.40–36.45% db) and carbohydrate (49.29–57.09% db). For each macadamia cultivar, while emulsion activities and emulsion stabilities of the TDF tended not to be different from those of the PDF (p > 0.05), TDF had significantly greater water absorption capacities (WAC), oil absorption capacities and foaming capacities (FC), but had significantly lower foaming stability (FS) than the PDF (p ? 0.05). The TDF from PY 741 cultivar possessed the highest WAC and FC but the lowest FS. The variation in the functional properties of the defatted flours could mainly arise from the difference in the quantity and characteristics of the proteins in the flours. Structure determination of macadamia flours showed that the proteins bodies and starch granules were embedded in kernel tissues. The starch granules were oval and approximately 10 μm in diameter.     

Modification of human cancellous bone using Thai silk fibroin and gelatin for enhanced osteoconductive potential

The modification of human cancellous bone (hBONE) with silk fibroin/gelatin (SF/G) using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxysuccini-mide (NHS) crosslinking was established. The SF/G solutions at a weight ratio of 50/50 and the solution concentrations of 1, 2, and 4 wt % were studied. SF/G sub-matrix was formed on the surface and inside pore structure of hBONE. All hBONE scaffolds modified with SF/G showed smaller pore sizes, less porosity, and slightly lower compressive modulus than unmodified hBONE. SF/G sub-matrix was gradually biodegraded in collagenase solution along 4 days. The hBONE scaffolds modified with SF/G, particularly at 2 and 4 wt % solution concentrations, promoted attachment, proliferation, and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (MSC), comparing to the original hBONE. The highest cell number, ALP activity and calcium production were observed for MSC cultured on the hBONE scaffolds modified with 4 wt % SF/G. The mineralization was also remarkably induced in the cases of modified hBONE scaffolds as observed from the deposited calcium phosphate by EDS. The modification of hBONE with SF/G was, therefore, the promising method to enhance the osteoconductive potential of human bone graft for bone tissue engineering.