Electrochemical Deposition of Polyelectrolytes Is Maximum at the Potential of Zero Charge.

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.

Changes in dietary fiber fractions and gut microbial fermentation properties of wheat bran after extrusion and bread making.

The dietary fiber in wheat bran, principally non-starch polysaccharides (NSP), is mostly water-unextractable and is poorly utilized by human gut microbiota. The purpose of this study was to determine the change in water-extractability of NSP in wheat bran upon extrusion and then to determine if extrusion impacts the availability of NSP for fermentation by the fecal microbiota during in vitro fecal fermentation. A secondary objective was to incorporate extruded bran into a product formulation to determine if changes in WE-NSP and NSP fermentation were maintained in a finished product. Bran was extruded using combinations of high or low moisture (15% and 30% wb) and high or low screw speed (120 and 250rpm). All extrusion conditions resulted in increases in WE-NSP and fecal microbiota short chain fatty acid (SCFA) production upon fermentation compared with unextruded bran. Low screw speed and low moisture resulted in the greatest increase in WE-NSP (3-fold) as well as the highest production of SCFA during fermentation (1.4-fold) compared with unextruded bran. Whole wheat breads containing extruded bran did not show increases in either WE-NSP or SCFA production compared with the control. In conclusion, extrusion of wheat bran increased WE-NSP, which enabled greater fermentability by human fecal microbiota. However, once extruded bran was used in a whole wheat bread formulation the changes in fermentation outcomes were no longer evident.