Broadband Dielectric Spectroscopy (BDS) investigation of molecular relaxations in durum wheat dough at low temperatures and their relationship with rheological properties

Nanoconfinement Enables Photoelectrochemical Selective Oxidation of Glycerol via the Microscale Fluid Effect

The glycerol oxidation reaction (GOR) run with photoelectrochemical cells (PECs) is one of the most promising ways to upgrade biomass because it is thermodynamically favorable, while irreversible overoxidation leads to unsatisfactory product selectivities. Herein, a tunable one-dimensional nanoconfined environment was introduced into the GOR process, which accelerated mass transfer of glycerol via the microscale fluid effect and changed the main oxidation product from formic acid (FA) to glyceraldehyde (GLD), which led to retention of the heavier multicarbon products. The rate of glycerol diffusion in the nanochannels increased by a factor of 4.92 with decreasing inner diameters. The main product from the PEC-selective oxidation of glycerol changed from the C1 product FA to the C3 product GLD with a great selectivity of 60.7%. This work provides a favorable approach for inhibiting further oxidation of multicarbon products and illustrates the importance of microenvironmental regulation in biomass oxidation.

Thermal and Dielectric Investigations of Polystyrene Nanoparticles as a Viable Platform-Toward the Next Generation of Fillers for Nanocomposites

Nanoparticles are often used as fillers for enhancing various properties of polymer composites such as mechanical, electrical, or dielectric. Among them, polymer nanoparticles are considered ideal contenders because of their compatibility with a polymer matrix. For this reason, it is important that they are synthesized in a surfactant-free form, to obtain predictable surface and structural properties. Here, we synthesized a series of polystyrene nanoparticles (PS NPs), by emulsion polymerization of styrene, using varying amounts of divinylbenzene as a crosslinking agent and sodium 4-vinylbenzenesulfonate as a copolymerizing monomer surfactant-"surfmer". Using "surfmers" we obtained surfactant-free nanoparticles that are monodisperse, with a high degree of thermal stability, as observed by scanning electron microscopy and thermogravimetric investigations. The prepared series of NPs were investigated by means of broadband dielectric spectroscopy and we demonstrate that by fine-tuning their chemical composition, fine changes in their dielectric and thermal properties are obtained. Further, we demonstrate that the physical transformations in the nanoparticles, such as the glass transition, can be predicted by performing the first derivative of dielectric permittivity for all investigated samples. The glass transition temperature of PS NPs appears to be inversely correlated with the dielectric permittivity and the average diameter of NPs.

Microwave Spectroscopy Investigation of Carasau Bread Doughs: Effects of Composition up to 8.5 GHz

Carasau bread is a flat bread, typical of Sardinia (Italy). The market of this food product has a large growth potential, and its industry is experiencing a revolution, characterized by digitalization and automation. To monitor the quality of this food product at different manufacturing stages, microwave sensors and devices could be a cost-effective solution. In this framework, knowledge of the microwave response of Carasau dough is required. Thus far, the analysis of the microwave response of Carasau doughs through dielectric spectroscopy has been limited to the dynamics of fermentation. In this work, we aim to perform complex dielectric permittivity measurements up to 8.5 GHz, investigating and modeling the role of water amount, salt and yeast concentrations on the spectra of this food product. A third-order Cole-Cole model was used to interpret the microwave response of the different samples, resulting in a maximum error of 1.58% and 1.60% for the real and imaginary parts of permittivity, respectively. Thermogravimetric analysis was also performed to support the microwave spectroscopy investigation. We found that dielectric properties of Carasau bread doughs strongly depend on the water content. The analysis highlighted that an increase in water quantity tends to increase the bounded water fraction at the expense of the free water fraction. In particular, the free water amount in the dough is not related to the broadening parameter γ2 of the second pole, whereas the bound water weight fraction is more evident in the γ2 and σdc parameters. An increase in electrical conductivity was observed for increasing water content. The microwave spectrum of the real part of the complex permittivity is slightly affected by composition, while large variation in the imaginary part of the complex dielectric permittivity can be identified, especially for frequencies below 4 GHz. The methodology and data proposed and reported in this work can be used to design a microwave sensor for retrieving the composition of Carasau bread doughs through their dielectric signature.

The Effect of Sea Salt with Low Sodium Content on Dough Rheological Properties and Bread Quality

The aim of this study was to analyze the effects of the addition of sea salt with low sodium content (SS) in a refined wheat flour at the levels of 0.3%, 0.6%, 0.9% 1.2% and 1.5% on the rheological properties of the dough during mixing, extension, pasting and fermentation and the bread quality in terms of bread physical properties, crumb and crust color, texture and sensory characteristics. According to the data we obtained, the SS presented a strengthening effect on the dough network by increasing its stability, dough development time, energy and resistance. Moreover, the SS addition resulted in an increase in dough extensibility, to a delay of the gelatinization process and an increase of the falling number value. The bakery products obtained with the SS were of a higher quality compared to the control sample, presenting better physical and textural characteristics, a darker color and being more appreciated by consumers with the increased level of SS addition in the wheat flour. According to the sodium content from the bread recipe, the bread samples obtained may be classified as products with a very low sodium content of up to a 0.6% SS addition in the wheat flour or with a low sodium content if at least 0.9% SS is contained in the bread recipe.