Starch-zein blends formed by shear flow

A newly in-house developed shearing device was used to explore the formation of new types of microstructures in concentrated starch-zein blends. The device allowed processing of the biopolymer blends under homogeneous, simple shear flow conditions. Water and glycerol were added as plasticizers. Different ratios (0-20% zein, dry basis) were used to study the influence of the matrix composition and processing conditions on the properties of the final material. The properties at large deformation were examined by tensile tests in two different directions (i.e. along the flow (∥) and in the vorticity (⊥) directions). The morphology of the blends observed by confocal scanning laser microscopy and field emission scanning electron microscopy showed that under shearless conditions, starch-zein formed a co-continuous blend. The application of shear transformed this structure into a dispersion, with zein as the dispersed phase. The size of the zein aggregates increased with zein concentration. A certain degree of anisotropy was found with the 10% zein blend at the highest shear rate applied . Here, the zein aggregates were slightly deformed along the shear flow (∥). Both microscopy and tensile tests indicated that the blends have no or weak adhesion between the zein and starch phases. The effect of zein particles on the mechanical properties followed a modified model used for particle-matrix materials with weak adhesion between the phases.     

Association Among Parental Substance Use Disorder, P300 Amplitude, and Neurobehavioral Disinhibition in Preteen Boys at High Risk for Substance Use Disorder.

The P300 amplitude of the event-related potential as a mediator of the association between parental substance use disorder (SUD) and child's neurobehavioral disinhibition was assessed. The P300 amplitude was recorded using an oddball task in sons of fathers having either lifetime SUD (n = 105) or no psychiatric disorder (n = 160). Neurobehavioral disinhibition was assessed using measures of affect regulation, behavior control, and executive cognitive function. Parental SUD and child's P300 amplitude accounted for, respectively, 16.6% and 16.8% of neurobehavioral disinhibition variance. Controlling for parental and child psychopathology, an association between parental SUD and child's P300 amplitude was not observed. It was concluded that the P300 amplitude does not mediate the association between parental SUD and child's neurobehavioral disinhibition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In situ compatibilization of starch-zein blends under shear flow

Starch-zein blends show poor adhesion between the two phases. Aldehyde starch was investigated as compatibilizer for these blends. Wheat starch was oxidized under mild conditions using sodium hypochlorite in the presence of the 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and NaBr to prepare aldehyde starch. The oxidized starch was characterized by Nuclear Magnetic Resonance and Rapid Visco-Analyzer. Starch-zein blends plasticized with water and glycerol were prepared using simple shear flow in an in-house developed shearing device. Different zein ratios were tested to study the influence of aldehyde starch on the properties of the final material. The morphology of the blends was observed with confocal scanning laser microscopy and scanning electron microscopy. Tensile tests were used to evaluate the performance of the material. Both microscopy and tensile tests indicated that the blends had improved adhesion between the zein and starch phases, probably by reaction between the aldehyde groups in the starch molecules and zein. The aldehyde starch also influenced the properties of the starch matrix (higher viscosity, larger breakdown), which shows that physical or chemical crosslinks were formed inside the starch matrix.