Array of Different Polyaniline-Based Sensors for Detection of Volatile Compounds in Gummy Candy

Aroma in foodstuff is considered an essential attribute since it is closely related to the consumer acceptance of foodstuffs. Electronic nose (e-nose) system is composed by an array of gas sensor and has emerged as a promising alternative for the aroma volatile compounds recognition. In this study, a lab-made e-nose system comprising of an array of different polyaniline-based sensors has been used for aroma discrimination (apple, strawberry, and grape) in gummy candy. The sensor array was comprised by interdigitated graphite electrodes, using tracing paper substrate and sensitive layer of polyaniline (Pani) obtained by in situ and interfacial synthesis deposited by the in situ adsorption polymerization of aniline and layer-by-layer (LbL) methods. The sensors were characterized in relation to humidity and the Pani-in situ/PSS LbL layer presenting the higher sensitivity, a quite interesting feature for its use as a gas sensor. It has been demonstrated that the lab-made e-nose has been highly efficient in the discrimination of different concentrations of aromas added to gummy candies with excellent sensitivity and a limit of detection in the range of parts-per-billion, so demonstrated the applicability in food matrices.     

Kinetic evaluation of phenol/aniline mixtures adsorption from aqueous solutions onto activated carbon and hypercrosslinked polymeric resin (MN200)

Kinetic adsorption of phenol and aniline from aqueous solution onto activated carbon and hypercrosslinked polymeric resin MN200 were evaluated in single and binary system. Larger phenol and aniline uptakes were observed for activated carbon in single as well as binary system, which can be attributed to the better physical properties of activated carbon, for instance larger surface area and micropore area. The kinetic experimental data was properly fitted by the pseudo-first and pseudo-second-order rate equations. A synergetic effect between solutes was observed since phenol and aniline sorption kinetic in binary system was faster than the individual sorption of each solute in single system, as well as a slight increase in the kinetic parameters obtained in binary system. The particle diffusion rate was defined as the rate limiting mechanism in the singles and binary system for phenol and aniline kinetic adsorption on both adsorbents. Two steps were markedly defined by the Weber and Morris intraparticle diffusion analysis for phenol and aniline onto both adsorbents. In binary systems, the intraparticle diffusion was influenced by the physical properties of adsorbents.     

The influence of citrate and tartrate on the electrodeposition and surface morphology of Cu–Ni layers

This study examined the influence of citrate and tartrate as complexing agents on the electrodeposition and surface morphology of Cu–Ni layers. The alloys obtained in the tartaric acid and sulphate baths were nobler than those obtained in the citric acid/citrate and citric acid/citrate/tartaric acid media. The results indicated that the complexing medium influences the nobility and the type of mass transport of the alloy formed. The morphology of the electrodeposited Cu–Ni layers changed from a rather porous appearance in the absence of the complexing agents to nodular, cracked mud and cauliflower appearances for the citric acid/sodium citrate/sodium sulphate medium, tartaric acid/sodium sulphate medium and citric acid/sodium citrate/tartaric acid/sodium sulphate medium, respectively. The chemical composition of the Cu–Ni layers revealed the preferential deposition of copper. The ultraviolet–visible spectrophotometry measurements indicated the occurrence of the d–d type transition, regardless of the complexing medium employed.     

Sunflower Protein Concentrates and Isolates Prepared from Oil Cakes Have High Water Solubility and Antioxidant Capacity

Increasing the applications of industrial by-products is of great interest. Therefore, in the present study, sunflower oil cake from a local oil manufacturing company was used to obtain soluble protein concentrates and isolates with different content of phenolic compounds. All the extraction procedures evaluated resulted in concentrates and isolates with water solubility higher than 75% but with different chemical composition, color and physicochemical properties (i.e. surface hydrophobicity, thermal stability, and polypeptide composition). Since no extraction process led to a complete extraction of phenolic compounds, all the products exhibited antioxidant activity, which depended on the concentration of such compounds. Phenolic compounds give a dark color to sunflower protein concentrates and isolates; nevertheless their final color tone was more dependent on the conditions used in the preparation process than on the amount of phenolic compounds in the product. The results demonstrate the value of sunflower industrial oil cake as a source of proteins with high water solubility, good physicochemical properties and antioxidant activity.     

Electrodeposition of pristine and composite poly(3,4-ethylenedioxythiophene) layers studied by electro-acoustic impedance measurements

Composite layers of poly(3,4-ethylenedioxythiophene) and diamond nanoparticles were prepared by an electrocodeposition procedure from an electrolyte containing the monomer 3,4-ethylenedioxythiophene and a suspension of diamond nanoparticles in acetonitrile/water mixtures. For the in situ monitoring of the deposition process we used piezoelectric quartz crystals with gold electrodes as substrates (electrochemical quartz crystal microbalance, EQCM). The inclusion of the diamond particles increases the stiffness of the layers. This effect can be directly quantified via the electroacoustic impedance of the quartz crystal. We use a mean field model for the interpretation of our EQCM data which yields the complex shear modulus of the composite layers. The volume fraction of diamond (as determined by ex situ XPS) enters as a parameter in the evaluation procedure. Finally, we could estimate the solvent content of the composite layers and the shear moduli of the pure dry PEDOT matrix.     

Development of a method to determine Ni and Cd in biodiesel by graphite furnace atomic absorption spectrometry

This paper proposes a low cost, simple, fast method for determining Ni and Cd in biodiesel samples by graphite furnace atomic absorption spectrometry (GFAAS). The method was evaluated in biodiesel from different sources. Tungsten was used as a permanent modifier and the samples were prepared in the form of microemulsions, by mixing about 0.5 g of biodiesel with 5 g of surfactant (Triton X-100) in volumetric flasks and completing the volume with HNO₃ 1% (v/v). The detection limits obtained for Ni and Cd in microemulsions were ≤0.9 and 0.1 μg L⁻¹, respectively. The relative standard deviation (% R.S.D., n = 12) was ≤8.20% for Ni (washed animal fat sample) and ≤4.71% for Cd (sunflower oil sample). Accuracy was checked based on addition and recovery experiments, which yielded recovery rates varying from 93% to 108% for Ni and from 98% to 116% for Cd. Sample preparation is rapid and easy, and the use of an inorganic standard for calibration makes this sample preparation procedure suitable for routine applications.     

Hollow cathode synthesis of crystalline CN films

We describe a novel carbon hollow-cathode RF plasma reactor which has been used to prepare deposits of carbon nitride. Results of the characterization of the deposits by Fourier transform infrared (FTIR) microscopy, Raman microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray analysis and X-ray diffraction are presented. The variation of the properties of the deposits as a function of the deposition conditions is discussed. The inclusion of small quantities of methane in the gas mixture was found to enhance the formation of the CN deposit, but for conditions of maximum enhancement C–H and N–H groups were observed in the deposit. Elemental analysis of the deposit showed that the nitrogen content was 57 at.%. A crystalline deposit was obtainable at low substrate temperatures, and the crystals were seen to grow preferentially on defects on the substrate surface.     

Surface properties,thermal, and mechanical characteristics of poly(vinyl alcohol)–starch‐bacterial cellulose composite films

Nanocomposite films for food packaging applications were developed using bacterial cellulose (BC) nanofibers in different amount in a poly(vinyl alcohol)/starch (PVA/St) matrix. In search of a better method to reduce the harmful ingredients in food packaging, the cellulose nanofibers were obtained by the mechanical defibrillation of BC pellicles thus avoiding the addition of chemicals in the final packaging material. Improved mechanical performances were obtained starting from just 1% BC nanofibers in PVA/St. Atomic force microscopy images showed a uniform dispersion of BC nanofibers on the surface of nanocomposites. A twofold increase of both tensile strength and modulus was obtained for 2 wt % BC in the composite. BC nanofibers have greatly improved the barrier properties of PVA/St matrix, a twofold increase of water vapor permeability being obtained for only 2 wt % BC nanofibers in the composite film. PVA/St/2BC was proposed as a high potential material for food packaging applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45800.     

An interpretation of neural networks as inference engines with application to transformer failure diagnosis

An artificial neural network concept has been developed for transformer fault diagnosis using dissolved gas-in-oil analysis (DGA). A new methodology for mapping the neural network into a rule-based inference system is described. This mapping makes explicit the knowledge implicitly captured by the neural network during the learning stage, by transforming it into a Fuzzy Inference System. Some studies are reported, illustrating the good results obtained.