Extraction of Total Phenolic Compounds, Flavonoids, Anthocyanins and Tannins from Grape Byproducts by Response Surface Methodology. Influence of Solid-Liquid Ratio, Particle Size, Time, Temperature and Solvent Mixtures on the Optimization Process

The current work concerns the optimization process of phenolic compounds solid liquid extraction from grape byproducts at high temperatures and short incubation times. The effect of five experimental parameters (solidliquid ratio, particle size, time, temperature and solvent mixture) mostly believed to affect the extraction process was undertaken. A first response surface methodology experimental design was used to optimize the solid-liquid ratio and milling time parameters. A second design was used for the optimization of the quantitative and qualitative parameters. The quantitative parameters studied are: total phenolic compounds, flavonoid content, total monomeric anthocyanin composition and tannin concentration. The qualitative parameters analyzed are: antiradical activity and antioxidant capacity. The second design was based on the use of time, temperature and solvent mixture as optimization parameters. The assays were first conducted separately revealing the best experimental conditions for the maximization of each response variable alone. A simultaneous response surface methodology of all the responses taken together was then conducted, showing the optimal extraction conditions to be: 93 minutes at 94?C and in 66% ethanol/water solvent. The maximal response values obtained for each parameter are: Total Phenolic Compounds yield (5.5 g GAE/100g DM), Flavonoid Content (5.4 g GAE/100g DM), Total Monomeric Anthocyanin yield (70.3 mg/100g DM), Tannin Concentration (12.3 g/L), Antiradical Activity (67.3%) and Total Antioxidant Capacity (393 mgAAE/L). All of the optimal values were acquired at 3 mL/g solid-liquid ratio and 6.8 min milling time. The obtained extracts could be used as natural bioactive compounds in several industrial applications.

Multiple Response Optimization of High Temperature, Low Time Aqueous Extraction Process of Phenolic Compounds from Grape Byproducts

In this study phenolic compounds extraction from grape byproducts was conducted using pure water as a solvent. High temperatures and low time incubation periods were used in the aim of reducing the cost of the process and heightening the phenolic compounds yield. Response surface methodology (RSM) was realized to study the effect of time and temperature on crushed and uncrushed grape pomace. The phenolic content was evaluated considering the quantity (total phenolics (TPC), flavonoids (FC), total monomeric anthocyanins (TMA) and tannins (TC)), and quality (antiradical activity (AA) and antioxidant capacity (AC)) of the extracts. High temperature low time extraction design used in this study was compared to the extraction process at moderate temperatures with relatively long periods of time. This was proved to ameliorate the quantitative extraction of phenolic compounds from grape pomace without affecting their bioactivity. Moreover, multiple response optimization showed the optimal extraction parameters to be 81?C and 140 minutes for the unmilled pomace samples, and 88?C and 5 minutes for the milled. TPC, FC, TMA, TC, AA and AC are almost the same for both optimums. Thus the possibility of replacing the milling process by the extraction time prolongation (for the unmilled pomace) of 135 minutes seems to be very plausible. HPLC analysis showed different quantity and diversity of extracted phenolics for the optimums. However this difference did not significantly affect the overall activity, showing that PC in the different extracts act in complete synergy all together leading to important biological properties. The obtained results using the extraction strategy adopted in this work could lead to several industrial applications.

An Environment Friendly, Low-Cost Extraction Process of Phenolic Compounds from Grape Byproducts. Optimization by Multi-Response Surface Methodology

Due to their beneficial effects on human health, phenolic compounds are increasingly attracting the attention of scientists and researchers all over the world. The main interest is in the extraction process of those natural plant-originated compounds from fruits, vegetables and plant wastes, namely grape wastes, in which phenolic compounds are the most abundant secondary metabolites. This waste exploitation not only re-assimilates those byproducts into the food cycle, but also avoids major environmental problems. Herein, the optimization of the phenolic compounds concentration and free radical scavenging activity from Cabernet Sauvignon grape byproducts was conducted, using multi-response surface methodology. A conventional solid-liquid extraction process was performed with pure water as a solvent to study the effects of both time and temperature on the procedure. The maximal phenolic compounds concentration (878.9 mg/L) was reached at 47℃ after 30 hours while the optimal free radical scavenging activity (41.15%) was obtained at 30℃ after 20 hours. A multi-response surface methodology compromised between the quantity and the quality of the extracted phenolics, and the parameters maximizing both responses were obtained at 37℃ and 28 hours. This low-cost and energy saving process provides an excellent tool for further industrial applications.

Electrosynthesis, Characterization and Electrocatalytic Behaviour of Organic-Metal Thin-Films Based on 2,2’-Bithiophene-5-carboxylic Acid and Metal Ions

2,2’-Bithiophene-5-carboxylic acid (BTA) thin-films on platinum (Pt) electrodes were electrochemically prepared in acetonitrile solution containing 0.1 M tetrabutylammonium perchlorate (TBAP) and 0.05 M BTA. These films were complexes with several metal ions such as Cu2+, Ag+ and Co2+. Their structural characteristics were compared with those of powder complexes chemically prepared from BTA and the corresponding metal ion. IR and XPS techniques reveal that the film complexes with metal ions have the same structures as the corresponding powder complexes. The electrocatalytic activity of BTA film-metal ions has been investigated toward ascorbic acid (AA) oxidation and compared to that obtained on a free BTA film. BTA film-metal ions exhibit good catalytic proprieties and better detection of AA than a free BTA film. This new propriety allows these films to be used as electrochemical sensors. This electronic document is a “live” template. The various components of your paper [title, text, heads, etc.] are already defined on the style sheet, as illustrated by the portions given in this document.

Continuous Ethanol Fermentation at Very High Gravity in the Presence of <i>Saccharomyces cerevisiae</i>: A Bifurcation Analysis

In this paper, a study of the bifurcation analysis of fermentation of sugar to ethanol in presence of Saccharomyces cerivisiae at very high gravity is described. The bifurcation analysis was done for a concentration 280 gl&minus;1 of sugar, and the dilution rate was taken as the parameter of bifurcation. Two Hopf bifurcations (HB) at 280 gl&minus;1 were found. At dilution rate of 0.027 h&minus;1 the system exhibits damped oscillations and not sustained oscillations as previously reported because the system is close to a point of attraction, and we can attenuate these oscillations by the choice of initial conditions. The system exhibits sustained oscillations between the two Hopf Bifurcations, the first at 0.08028 h&minus;1 and the second at 0.04395 h&minus;1. These oscillations are the consequence of synchrony between the daughter and the mother yeast. Indeed, it is better to take a dilution rate between the two Hopf bifurcations (self sustained oscillations), in order to increase the ethanol productivity.

Reactivity of Nanostructured MnO_2 in Alkaline Medium Studied with a Microcavity Electrode: Effect of Oxidizing Agent

The synthesis of MnO2 powders by hydrothermal method with different oxidizing agents has been successfully achieved. The characterizations by scanning electron microscopy, energy-dispersive X-ray analyses, transmission electron microscopy, and X-ray diffraction techniques confirm the synthesis of nanostructured γ-MnO2 powders. The electrochemical reactivity of these powders in 1 mol/l KOH is investigated by cyclic voltammetry and electrochemical impedance spectroscopy （EIS） by using microcavity electrode. The results reveal that the MnO2 synthesized with Na2S2O8 shows the highest electrochemical reactivity in the test medium. This is due both to its large expanded surface area and its crystallographic variety γ-MnO2 formed in the matrix of ramsdellite, which is largely used as cathodic material for primary batteries. However, the presence of pyrolusite in the structure of γ-MnO2 synthesized with （NH4）2S2O8 decreases its electrochemical reactivity due to its narrow 1×1 size tunnel, which hinders the protons insertion.

X-ray Structure and Density Functional Theory Investigations of 4-((2R)-2-(3,4-dibromophenyl)-1-fluoro cyclopropyl)-N-(o-tolyl)benzamide Compound

In this work,the structure of 4-((2R)-2-(3,4-dibromophenyl)-1-fluorocyclopropyl)-N-(o-tolyl)benzamide(DBFB)has been determined at room temperature using single-crystal X-ray diffraction data.The structure of the compound was solved using 1464 observed reflections with I≥2σ(I).It crystallizes in monoclinic space group P21 with a=20.0820(10),b=10.2770(10),c=4.860(2)?,β=95.9600(10)°,V=997.6(4)?3,Z=2,Dc=1.675 g/m3,F(000)=500,Μr=503.18,μ=4.09 mm-1 and the final R=0.0639.The molecular packing of the title compound exhibits C–H???O and C–H???F hydrogen bonds forming a supramolecular network.Furthermore,conformational analysis has been performed in order to confirm the most stable conformer of the title compound.Geometrical parameters of the keto conformer in the ground state have been obtained using density functional theory(DFT)method with B3LYP/6-31G(d,p)level of theory.In general,a good agreement between the calculated and experimental results was observed.The normal modes of vibration,molecular boundary orbitals(HOMO and LUMO),reactivity descriptors,Mullikan atomic charges and molecular electrostatic potential for the title compound have been evaluated and discussed.

A comparative study of a direct and pulse electrodeposition method of TiO_(2)films and its effect on photoelectrocatalytic degradation of methyl orange dye

The present study reports the titanium dioxide(TiO_(2))films synthesized from TiCl3 precursor on ITO glass substrates using two electrochemical techniques,namely direct electro-deposition(DE)and pulse electro-deposition(PE).The synthesis potential during the time-on(Ton)period was fixed at-1.5 V.However,the open-circuit potential was applied during the time-off(Toff)period.The effect of the technique of electro-deposition and Toff duration on the properties of TiO_(2)films and their photoelectron-catalytic activity were investigated.The obtained films were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),UV-VIS spectrometer,and photocurrent measurement respectively.It is found that the use of the PE technique at different Toff improves the properties of TiO_(2)films compared to the DE technique.The XRD patterns show the anatase phase with a marked preferential orientation along the(101)direction for all samples.From the SEM analysis,it is seen a significant change from big multigrain agglomerates at DE to a dense film structure and small multigrain agglomerates at different Toff.As the Toff decreases from 3 s to 1 s,the photocurrent response rises and reaches a high value of about 12 m A/cm^(2).Compared with DE,and under UV light the photocatalytic property of TiO_(2)film synthesis via PE has been improved in the degradation of methyl orange(MO).Finally,the films deposited at low Toff(Toff=1 s)show a faster degradation of MO.