Modulation and Characterization of the Double Network Hydrogel Surface-Bulk Transition

The hydrogel chemical structure at the gel-solution interface is important toward practical use, especially in tough double network (DN) hydrogels that have promising applications as structural biomaterials. In this work, we regulate the surface chemical structure of DN hydrogels and the surface–bulk transition by the molding substrate used for the synthesis of the second network. To characterize the surface and bulk structure, we combined attenuated total reflectance Fourier-transform infrared spectroscopy and a newly developed microelectrode technique that probe the electric potential distribution within a hydrogel. We found that the polymerization on a repulsive substrate leads to the formation of a thin layer of a second network on the surface of DN hydrogels, which makes the surface different from the bulk. By controlling the second network polymerization conditions and molding substrate, the surface–bulk transition region can be regulated, so that either only the second network or both networks are present at the DN hydrogel surface. Through these findings, we gained a new insight into the structure formation at the DN hydrogel surface, and this leads to easy regulation of the hydrogel surface structure and properties

Effect of physicochemical and empirical rheological wheat flour properties on quality parameters of bread made from pre-fermented frozen dough

The objective of this study was to examine the influence of flour quality on the properties of bread made from pre-fermented frozen dough. The physicochemical parameters of 8 different wheat flours were determined, especially the protein quality was analysed in detail by a RP-HPLC procedure. A standardized baking experiment was performed with frozen storage periods from 1 to 168 days. Baked bread was characterised for specific loaf volume, crumb firmness and crumb elasticity. The results were compared to none frozen control breads. Duration of frozen storage significantly affected specific loaf volume and crumb firmness. The reduction of specific loaf volume was different among the used flours and its behaviour and intensity was highly influenced by flour properties. For control breads wet gluten, flourgraph E7 maximum resistance and RVA peak viscosity were positively correlated with specific loaf volume. However, after 1\u201328 days of frozen storage, wet gluten content was not significantly influencing specific loaf volume, while other parameters were still significantly correlated with the final bread properties. After 168 days of frozen storage all breads showed low volume and high crumb firmness, thus no significant correlations between flour properties and bread quality were found. Findings suggest that flours with strong gluten networks, which show high resistance to extension, are most suitable for frozen dough production. Furthermore, starch pasting characteristics were also affecting bread quality in pre-fermented frozen dough