Effect of different extrusion methods on physicochemical properties and qualities of noodles based on rice flour.

Rice noodles have been manufactured in the food industry using different extrusion methods, such as traditional and modern extrusions, which affect the noodle structure and qualities. Therefore, the effects of the extrusion process on qualities of rice noodles using the same blend of rice flour and crosslinked starch were evaluated. In this study, a capillary rheometer was used as an alternative approach to simulate the traditional extrusion method in which the noodles are obtained by continuously pressing the pregelatinized noodle dough through a die. For modern extrusion, a twin-screw extruder was employed to obtain the noodles in a one-step process. The optimal range of moisture content used in the formulation was studied. Upon cooking, the noodles showed a decrease in cooking time and cooking loss with increasing moisture content in the formulation. All cooked noodles showed comparable tensile strength, but those extruded by a twin-screw extruder had substantially greater elongation. Scanning electron micrographs revealed that the noodles prepared using the extruder had a denser starch matrix, while those obtained from a capillary rheometer showed the aggregation of starch fragments relevant to the existence of starch gelatinization endotherm from differential scanning calorimetry. This indicated that the extrusion process using the twin-screw extruder provided a more uniform starch transformation, i.e., more starch granule disruption and gelatinization, thus giving the noodles a more coherent structure and better extensibility after cooking. The obtained results suggested that different thermomechanical processes used in the noodle industry gave the extruded rice noodles different qualities respective to their different microstructures.

Roles of viscosity, applied load and surface wettability on the lubrication behaviour of model liquid/semi-solid foods: Measurements with a bespoke tribo-cell fixture and rotational rheometer.

Thin film sliding and friction phenomena of food bolus confined between tongue-palate surfaces during oral processing can be explored using tribological measurements. However, these measurements are still limited within the food industry due to the requirement of expensive commercial instruments which are not commonly used in the food industry. This work has designed and manufactured a modular "tribological cell" (tribo-cell) that can simulate lubricated soft-hard contact interfaces and can be mounted on a rotational rheometer to perform tribological measurements. The tribo-cell was validated by performing tribological measurements using a range of corn syrup solutions as model liquid foods. It was shown that the Stribeck curve describing the change in friction behaviour with entrainment speed or with the product of entrainment speed and liquid viscosity could be obtained. Since tribology deals with surface property, the cell was then used in the further studies to demonstrate the effects of applied normal load and surface wetting on the tribological response of lubricated hard-soft contact of the designed fixture. These parameters were shown to have a marked influence on in the boundary and mixed-lubrication regimes. The designed tribo-cell was also used to illustrate the impact of fat content on the lubrication properties of commercial liquid and semi-solid foods with different fat contents, thus, pointing out to the importance of tribology as a vital tool for product formulation designs in food and beverage industry.

Electromechanical properties of multi-walled carbon nanotube/gelatin hydrogel composites: effects of aspect ratios, electric field, and temperature.

The effects of multi-walled carbon nanotube (MWNT) aspect ratio, electric field strength and temperature on the electromechanical properties of MWNT/gelatin hydrogel composites were investigated. The highest aspect ratio of MWNT provides the composites with the highest dynamic moduli under electric field. The MWNT/gelatin hydrogel composites of 0.01, 0.1, 0.5, and 1 vol.% and the pure gelatin hydrogel possess the storage modulus sensitivity values of 0.69, 1.23, 0.94, 0.81 and 0.47, respectively, at 800 V/mm. The results can be interpreted in terms of the enhanced polarizability between the carboxyl groups of gelatin under the presence of MWNT. The effect of temperature on the electromechanical properties of MWNT/gelatin hydrogel composites investigated between 30 °C and 90 °C shows three distinct regimes of temperature-dependent storage modulus behavior. In the deflection testing, the effects of electric field on the deflection distance and the dielectrophoresis force of the MWNT/gelatin hydrogel composites were also investigated. MWNT/gelatin hydrogel composites suspended in the silicone oil between electrodes, respond rapidly with a deflection toward the anode site, indicating the attractive force between anode and the polarized carboxyl group as the gelatin structure possesses negative charges.

Nondestructive rheological measurement of aqueous dispersions of solid lipid nanoparticles: effects of lipid types and concentrations on dispersion consistency.

PURPOSE: To investigate dispersion consistency of solid lipid nanoparticles as functions of lipid types and concentrations. METHODS: Viscoelastic measurement at an application of low stress was employed to characterize the internal microstructure developed within the dispersions. Pure triglycerides with different length of fatty acid chains, trimyristin (C14), tripalmitin (C16), and tristearin (C18) were studied with respect to the partial triglyceride with C22 chain length (Compritol 888 ATO), and cetyl palmitate wax (C16). RESULTS AND DISCUSSION: Increasing fatty acid chain length of triglycerides induced more particle shape anisometry; therefore, elastic behavior of triglyceride dispersion increased in sequence of trimyristin < tripalmitin < tristearin. Because of an imperfect crystalline structure, Compritol 888 ATO particles yielded the dispersion with a less elastic behavior. Despite having an equal fatty acid chain length (C16), cetyl palmitate wax provided the dispersion with lower network strength than tripalmitin as a result of the lower ordered crystal packing of fatty acid chains in the wax particle. Increasing lipid concentration improved the dispersion consistency owing to the more pronounced interaction between lipid particles. Data obtained from particle size analysis did not help explain the resulting microstructures in relation to the types and concentrations of lipid. CONCLUSIONS: A nondestructive rheological experiment is a powerful tool in revealing the microscopic structures of SLNs, which provides the information on viscous and elastic behaviors, corresponding to the internal structure of the dispersions. Consequently, viscoelastic data might assist pharmaceutical industry in selecting type of lipid appropriate for developing SLN formulations with the desired consistency.

Rheological and morphological characterizations on physical stability of gamma-oryzanol-loaded solid lipid nanoparticles (SLNs).

In the present study, gamma-oryzanol was incorporated into glycerol behenate (Compritol 888 ATO) nanoparticles (SLNs) at 5 and 10% (w/w) of lipid phase. Increasing lipid phase concentration resulted in increased consistency and particle diameter of SLNs. Upon storage over 60 days at 4, 25 and 40 degrees C, the instability was observed by rheological analysis for all samples due to the formation of gelation. Rheological measurement revealed the increase in storage modulus and critical stress during storage at all temperatures. However, at 40 degrees C, the pronounced instability was observed from the highest increase in storage modulus and a formation of rod-like network structure from scanning electron micrographs. An increase in crystallinity, determined by differential scanning calorimetry, was also found during storage at all temperatures, confirming the instability of SLNs. Particle diameters and zeta potentials of both concentrations at all storage conditions failed to explain the observed instability. These investigations may help to develop formulations of solid lipid nanoparticles, which are optimized with respect to the desired rheological properties.