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A B S T R A C TResistant starch (RS) has shown benefits to gastrointestinal health, but it is present in only small amounts in most grain-based foods. The purpose of this study was to increase RS in whole wheat flour to improve its potential health benefits. Zero to 7 cycles of cooking (20 min, boiling water) and freezing (−18°C, 23 h) of whole wheat flour in water (1:15 %w/v) were performed. Increasing cooking-freezing cycles increased RS from 1.03 to 8.07% during in vitro starch digestion. During in vitro fecal fermentation, increasing cooking-freezing cycles increased short chain fatty acids, mainly propionate. Increases in butyrate were also noted during the first 8 h of fermentation. All flours resulted in significant increases in Bifidobacterium of >0.5 log during fermentation compared to baseline. Thus, even modest increases in the RS content of whole wheat flour modulated the metabolic activity of gut microbiota to increase production of beneficial metabolites.

electrolytes emerge from two rather disparate properties. Like oxide-free noble metals, graphene is electrically conducting. [3] However, similar to other carbonaceous materials, it is considered largely hydrophobic, [4] given some contribution from hydrocarbon contamination on the surface. [5] As a result, the ions will be attracted to the surface due to conductivity (i.e., image charge), but the hydrophobicity will tend to repel them. [6] As a result, the interface of electrolyte with graphene is unusual. It is experimentally shown by X-ray reflectivity [7] and supported by simulation [7] that the interface of graphene supported on a metal will also have an ≈1 nm thick low density water layer (also called "vacuum layer"), consistent with other hydrophobic surfaces. [8] To reconcile the hydrophobic and electrically conducting nature of graphene, simulation studies show a formation of a "hydrophobic" hydration layer on the interface between the graphene and the bulk aqueous solution; [4a,9] There are two hydration layers, at ≈0.3 and ≈0.6 nm, and the ions in the solution appear to disrupt the layer farther from the interface. [9b] Simulation of electrowetting on graphene/metal surface shows that the polarization of hydration layer causes dramatic and complete screening of the electric field on graphene. [9c] It was estimated, that hydration screens over 85% of ion-graphene molecular electric field. [9d] Simulation on the dynamics of the hydration layers shows that the negative potential is more disruptive. [9e] Experimentally, the formation and the structure of hydration layer was measured by scanning probe microscopy [10] and X-ray reflectivity. [11] An interesting experimental evidence of the hydrophobic hydration layer is the reversible wettability of graphene on UV exposure that forms oxygen and hydroxyl radicals that react with graphene to make the interface hydrophilic which can be reversed to hydrophobic surface on storing in the dark. [12] By contrast, simulations of density fluctuations at the interface point to a hydrophilic nature of graphene, [13] which have also been concluded by contact angle measurements on free standing films. [14] Furthermore, the low density of states compared to metals at the Dirac Point gives rise to quantum capacitance that lowers the overall interfacial capacitance. [15] Thus, the electrostatics of electrolyte/graphene interface that affects a range of electrochemical application remains a subject of intense research with potentially undiscovered phenomenon.Here, the dynamic nature of the interface was experimentally studied by differential reflectivity to probe the electrostatics Unlike metals, graphene forms a hydration layer at the electrode/electrolyte interface, which is unusual for a conducting material. Here, the electrostatic properties of the hydration layer are studied by measuring the oscillation of ions at the interface due to an applied AC potential by differential reflectivity during cyclic voltammetry (CV). The amplitude of ion oscillation at picomet...

Electrochemical deposition of cationic and anionic polyelectrolyte on a Au electrode is studied as a function of applied potential between the electrode and the solution of monovalent electrolyte. The deposition is measured by open circuit potential relative to a pristine electrode in a reference solution (100 mM NaCl). The rate of deposition is measured by a home-built electrochemical-optical method in real time. It was discovered that the polarity of the potential and magnitude of the potential are not the primary reasons to enhance deposition. For example, both the amount and rate of deposition of negatively charged poly-(styrenesulfonate) in NaCl are higher when the electrode is at −200 mV than at +200 mV with respect to the solution. The results are explained in terms of the charge state of the electrical double layer that is primarily controlled by supporting (small) ions.