Effect of Support Matrix and Crosslinking Agents on Nutritional Properties of Orange Juice during Enzyme Clarification: A Comparative Study.

This study investigated the impact of a support matrix and active group on the support to the nutritional properties of orange juice after juice clarification. Pectinase was immobilized on chitosan and aminated silica supports, activated with genipin or glutaraldehyde, and applied for juice clarification. The effects on various juice properties, including reducing sugars, total soluble solids, vitamin C, and phenolic compounds, juice color, and pH, were evaluated. The results revealed that the immobilization on chitosan activated using genipin resulted in the highest biocatalyst activity (1211.21 U·g-1). The juice treatments using the biocatalysts led to turbidity reduction in the juice (up to 90%), with the highest reductions observed in treatments involving immobilized enzyme on chitosan. Importantly, the enzymatic treatments preserved the natural sugar content, total soluble solids, and pH of the juice. Color differences between treated and raw juice samples were especially relevant for those treated using enzymes, with significant differences in L* and b*, showing loss of yellow vivid color. Analysis of phenolic compounds and vitamin C showed no significant alterations after the enzymatic treatment of the raw juice. According to our results, the clarification of orange juice using immobilized enzymes can be a compromise in turbidity reduction and color reduction to maintain juice quality.

Characterization of dielectric properties of residual ashes obtained from rice husk and annoni grass.

This paper presents a study about the characterization of dielectric properties (dielectric constant [Formula: see text] and dielectric-loss constant [Formula: see text]) of samples derived from two different biomass types: rice husk ash (RHA) and annoni grass ash (AGA).The procedure is carried out using the resonant cavity method along with a vector network analyzer. For this purpose, four different ashes were produced, by burning rice husk and annoni grass at two different temperatures and burning times: 400 °C/30 min (RHA40030 and AGA40030) and 800 °C/5 h (RHA8005h and AGA8005h). These ashes were combined with Bakelite to produce cylindrical samples with diameter of 30 mm and thickness of 4.5 mm, which were characterized considering the frequency in the test band for 5G technologies ([Formula: see text] GHz). Experimental results showed that the samples burnt at high temperature showed very high [Formula: see text] when compared to the samples burnt at low temperature, mainly for AGA8005h. These values are [Formula: see text] 0.1690 and 1.4900 for RHA8005h and AGA8005h, respectively. The resulting dielectric constants are [Formula: see text] = 3.87 for RHA8005h and [Formula: see text] = 15.14 for AGA8005h). These very high dielectric loss tangent, indicate that these materials exhibit formidable properties for electromagnetic energy absorption, hence allowing the application as radiation-absorbent material (RAM).

New strategy to obtain high surface area anatase nanotube/AuNP photocatalyst.

Anatase nanotubes with high surface area (ca. 350 m2 g-1), containing gold nanoparticles, were successfully obtained from trititanate nanotubes, prepared by a template-free hydrothermal method, and calcined at 450 °C. The high surface area and tubular morphology were attained due to the presence of ionic silsesquioxane, which acts as anti-sintering agent for titania during calcination process, by forming a thin silica coating between anatase nanotubes. Additionally, the ionic silsesquioxane also acts as stabilizing and adhesion agent for gold nanoparticles on the surface of anatase nanotubes. The influence of the ionic silsesquioxane on the morphological and textural properties of anatase nanotubes was studied in three different moments during the synthesis: before, after and before/after nanotubes were rolled up. The photocatalytic activity of the nanotube samples was evaluated by hydrogen generation showing remarkable enhancement in hydrogen production and stability of catalyst when compare with the bare anatase sample and commercial P-25.

Silver bonded to silica gel applied to the separation of polycyclic aromatic sulfur heterocycles in heavy gas oil.

Silica gel containing silver ions was prepared and characterized. Silica was organofunctionalized with 3-mercaptopropyl group by using grafting reaction followed by silver ions adsorption (silver covalently bonded to mercaptopropyl silca gel, Ag-MPSG). The organofunctionalization and silver coordination were observed by transmission infrared spectroscopy and elemental analyses (CHN and EDS). The textural characteristics were studied by N2 adsorption-desorption isotherms. Additionally, optical properties were studied by diffuse reflectance spectroscopy. The Ag-MPSG material was employed as stationary phase for the first time for fractionation of a heavy gas oil sample resulting in a fraction that is richer in polycyclic aromatic sulfur heterocycles (PASH). The fractions were analyzed by comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detector and Ag-MPSG material provided similar fractionation performance when compared to conventional material [palladium covalently bonded to mercaptopropyl silca gel, Pd(II)-MPSG] usually employed for the same purpose and as the cost of silver is less than the one of palladium, the cost of the fractionation phase was reduced.

Development of active biofilms of quinoa (Chenopodium quinoa W.) starch containing gold nanoparticles and evaluation of antimicrobial activity.

Active biofilms of quinoa (Chenopodium quinoa, W.) starch were prepared by incorporating gold nanoparticles stabilised by an ionic silsesquioxane that contains the 1,4-diazoniabicyclo[2.2.2]octane chloride group. The biofilms were characterised and their antimicrobial activity was evaluated against Escherichiacoli and Staphylococcusaureus. The presence of gold nanoparticles produces an improvement in the mechanical, optical and morphological properties, maintaining the thermal and barrier properties unchanged when compared to the standard biofilm. The active biofilms exhibited strong antibacterial activity against food-borne pathogens with inhibition percentages of 99% against E. coli and 98% against S. aureus. These quinoa starch biofilms containing gold nanoparticles are very promising to be used as active food packaging for the maintenance of food safety and extension of the shelf life of packaged foods.

Silver nanoparticle-ionic silsesquioxane: a new system proposed as an antibacterial agent.

Spherical silver nanoparticles with an average size of ca. 5 nm were synthesized in aqueous medium using a charged silsesquioxane containing a quaternary ammonium group, the bridged 1,4-diazoniabicyclo[2.2.2]octane nitrate, as a stabilizer and size controller. For the first time this system was synthesized and applied as an antibacterial agent and its activity was confirmed with excellent results. The new system shows high stability, which can be confirmed by the unchanged UV-Vis band even one year later. The magnitude of the zeta-potential (ζ) (+24.7 mV) indicated electrostatic contribution for the silver nanoparticles stability and the signal showed that the nanoparticles have a positively charged surface. In vitro antibacterial tests were performed against E. coli, P. aeruginosa and S. aureus bacteria, and the minimum concentrations of silver in the nanoparticle form for complete inhibition of bacteria were 0.60, 1.1 and 2.0 µg mL-1, respectively. These values are very low when compared to the previous reports, making this system very promising. The cytotoxicity assay showed that these silver nanoparticles are safe for mammalian cells at the studied concentrations.

Ionic silica based hybrid material containing the pyridinium group used as an adsorbent for textile dye.

The present study reports the development of an ionic silica based hybrid material containing the cationic pyridinium group, which was employed for the removal of the Reactive Red 194 textile dye from aqueous solution. Three hybrid material samples were prepared with planned textural and chemical properties, varying the inorganic precursor molar percentage in the sol-gel synthesis. The obtained samples were defined as Py/Si-90, Py/Si-92 and Py/Si-94, where the number specifies the inorganic molar percentage. The hybrid samples were characterized by elemental, infrared, (13)C and (29)Si NMR, N(2) adsorption-desorption isotherms and thermogravimetric analyses. The dye-removing ability of these adsorbents was determined by the batch contact adsorption procedure. Effects such as pH value and adsorbent dosage on the adsorption capacities were studied. Four kinetic models were applied. The adsorption was best fitted to Avrami fractional-order kinetic model for the three hybrid material samples. The kinetic data were also adjusted to an intra-particle diffusion model resulting three linear regions, indicating that the adsorption kinetics follows multiple sorption rates. The equilibrium data were fitted to Langmuir, Freundlich and Liu isotherm models. The maximum adsorption capacities were 165.4, 190.3 and 195.9 mg g(-1) for Py/Si-90, Py/Si-92 and Py/Si-94, respectively. Simulated dye-house effluents were used to check the applicability of the proposed adsorbents for effluent treatment. Dye loaded adsorbents were regenerated (>98.2%) by using 0.4 mol L(-1) of NaOH solution as an eluent.