DETERMINATION OF PARAMETERS AND PRETREATMENT SOLUTION FOR GRAPE DRYING

The drying of Iranian seedless white grapes (sultana) was investigated in a batch operation in a laboratory dryer. The effect of pretreatment and temperature on the drying rate of grapes at constant air velocity were studied. Pretreatment solutions contained different alkaline materials in different concentrations and temperatures. Dipping grapes in an alkaline solution increased the drying rate substantially. Increasing the air temperature in the dryer from 60 to 70°C accelerated the drying rate (for a decrease in drying time) of the pretreated grape. Grapes dried in 450–900 min depending on pretreatment and air temperature. The shorter drying time and best quality dried product were obtained with grapes dipped in a solution of potassium carbonate of 5% at 42°C. The mean apparent diffusivity of moisture for K₂CO₃ pretreatment was calculated at 50, 60, and 70°C, and the values were fitted to an Arrhenius type model. Moisture sorption isotherms of currants were determined at 20, 30, and 40°C using static gravimetric methods. A modified Halsay equation was used to predict experimental data for water activity in a range of 0.1–0.85.     

EFFECTS OF VARIOUS TREATMENTS ON THE DRYING KINETICS OF Muscatel GRAPES

ABSTRACT

The drying kinetics of Muscatel grapes at 60°C and a relative air humidity of 22% were determined after various pretreatments had been applied to the grapes. The pretreatment parameters varied were the chemical agent (potassium carbonate solution with or without olive oil, or sodium hydroxide solution); the duration of pretreatment; and the temperature and concentration of the solution. A 3 minute pretreatment with an aqueous solution of K₂CO₃ and olive oil at 60°C reduced drying time from about 80 h to 20 h. Optimal drying load corresponded to a single layer of almost close-packed grapes on each tray. The experimental drying kinetics were satisfactorily reproduced by a model in which both grape size and the effective coefficient of diffusion are functions of moisture content.     

Heat pump drying of grape pomace: Performance and product quality analysis

Abstract

Grape is one of the most popular fruits and various types of grape have been cultivated by more than 100 countries around the World. The wine and juice industry produces large quantities of by-product, called grape pomace (GP) as an industrial waste and it consists of skins, seeds, and stems. Various processes such as separation, pressing, drying, and milling are applied to benefit from its health effects. In this study, the seeded black GP Kalecik karas? (Vitis vinifera) was dried in an assisted closed cycle heat pump dryer (HPD) designed for high-moisture products to investigate the drying behaviors of GP. The effects of drying air temperature on bioactive properties and the drying characteristics of GP, and performance of system have discussed. Experiments were carried out at two different temperatures (45 and 50°C) and air velocity of 1.0 m/s. It was seen that increasing temperature decreased the drying time, coefficient of performance of whole system (COP_ws), and specific energy consumption (SEC). The average values of COP_ws for temperatures 45°C and 50°C were calculated as 3.28 and 3.10, respectively. The drying efficiencies (DE) at drying air temperature of 45°C and 50°C ranged from 2 to 12% and from 2 to 15%, respectively. Additionally, result of analysis has indicated that using a HPD at lower temperatures increases performance of system despite of higher energy input. Bioactive properties of dried samples at drying air temperature of 45°C are better than 50°C. The results show that drying the GP at low temperature is more suitable for product quality. For this reason, heat pump may be preferred. It shows that this drying system with higher capacities in the future can be recommended as an alternative technique in terms of energy usage, drying time, and performance of system.     

Antioxidant Activity of Hybrid Grape Pomace Extracts Derived from Midwestern Grapes in Bulk Oil and Oil‐in‐Water Emulsions

Natural antioxidants to inhibit oxidation in edible oils are in high demand. Grape pomace is an abundant, inexpensive source of polyphenolic antioxidants, which are responsible for numerous health benefits. We examined pomace from eight varieties of Midwestern hybrid grapes for phenolic content and antioxidant activity. Ethanolic extracts produced from the pomace of each grape variety were added to two model systems, bulk soybean oil and oil‐in‐water emulsions, to determine antioxidant activity. Oxidation was monitored in each model system at a temperature appropriate to that particular system. While the extracts had relatively little effect in bulk oil, we observed dose‐dependent antioxidant effects of some extracts in oil‐in‐water emulsions. Oxidation in bulk oils was assessed via total polar compounds and polymerized triacylglycerols. Oxidation in emulsions was assessed by peroxide value, headspace oxygen measurements, gas chromatography of headspace volatiles, and fatty acid analysis. Pomace extracts derived from red grapes generally outperformed those from white grapes, with the Marechal Foch variety showing high antioxidant activity at intermediate concentrations. At higher concentrations, Marechal Foch, Corot Noir, Frontenac, and Norton extracts showed promising antioxidant activity. This is the first report on antioxidant activity in an oil and emulsion setting for many of these grape varieties.     

Decomposition in the field of residues of oilseed rape grown at two levels of nitrogen fertilisation. Effects on the dynamics of soil mineral nitrogen between successive crops

The decomposition of oilseed rape residues of different quality and its effects on the mineral N dynamics of the soil in the period between crops were studied in situ. The residues studied were obtained by growing an oilseed rape crop at two levels of N fertilisation, 0 and 270 kg N ha^-1. The study was carried out using two types of experiment: field plots and cylinders filled with disturbed soil and inserted into the soil. The decomposition of the residues was followed using an approach involving the dynamics of both carbon and nitrogen, the parameters measured being the CO₂ emitted from the soil, the soil mineral N content, the C present in soluble form or in the form of microbial biomass, and the C and N present in the form of plant residues.The two residues studied, of similar biochemical composition, and differing only in their N content, were rapidly mineralised: approximately 50% of the carbon in the residues was decomposed during the first two months following incorporation into the soil. The carbon mineralised in the form of CO₂ was largely related to the C present in the residues, no relationship having been found with the C present in soluble form or in the form of microbial biomass.Calculation of net N mineralisation from the residues using a model of mineralisation and leaching has provided evidence of an immobilisation phase for soil mineral N, during the first steps of residues decomposition. Labelling the high-N residues with ¹⁵N has moreover enabled us to demonstrate the low availability of the organic N from this residue, 20.8% of the organic N being mineralised in the course of 18 months of experimentation. Eventually, only the highest-N content residue resulted in a mineral N surplus in the soil, equivalent to 9 kg N ha^-1, by comparison with the control soil. Finally, this study has provided good evidence of the complementarity between the two experimental methods. The cylinders of disturbed soil gave a precise measurement of the decomposition of the residues, especially by means of monitoring soil respiration. The field plots were used to monitor the dynamics of soil mineral N which were calculated with the aid of a mathematical model of mineralisation and leaching of nitrogen in the presence and absence of residues.     

Varietal Relationship Between Skin Break Force and Off-Vine Withering Process for Winegrapes

This article presents a detailed study on the influence of winegrape variety, skin hardness of fresh berries, and withering thermo-hygrometric conditions on the dehydration kinetics of the grape. Although some works focused on the changes in the weight loss rate during grape dehydration under different environment conditions for several varieties, the combined effect of the skin mechanical properties and the thermo-hygrometric conditions has not been previously considered. The skin break force was confirmed as the varietal marker. Furthermore, its role in the selection of the withering conditions was assessed. The fresh grape berries were classified into two groups (soft and hard) according to the skin break force, and four off-vine withering conditions were evaluated. The softer skins facilitated the dehydration process increasing the weight loss rate, but the increase was significant only at low temperatures. The increase in temperature and/or decrease in relative humidity was beneficial to the grape dehydration process. A weight loss of about 50% after 12 days of withering was achieved at an air temperature of 28°C and relative humidity of 40%. Under the same dryer environmental conditions, a certain varietal effect on the dehydration kinetics was observed because a faster weight loss occurred for those grapes characterized by lower values of skin break force. These results suggest that the grape dehydration rate, influencing the quality of dessert wines, should be planned considering the skin hardness of fresh berries and the withering conditions. The skin break force represents a new variable that should be considered in modeling the withering process and in selecting, prior to harvest, the most appropriate vineyard for the dessert wines desired.     

Feasibility of creating compression‐molded biocomposite boards from berry fruit pomaces

In this study, we investigated the feasibility of creating biocomposite boards from berry fruit pomaces on the basis of a crosslinking mechanism. Blueberry, cranberry, and wine grape pomaces were ground, dried, and mixed with soy flour (SF) or pectin and xanthan gum mixture at a ratio of 1 : 1 and with the addition of 15% glycerol (w/w of pomace and SF). Blueberry pomace (BP) was also blended with NaOH‐modified soy flour (MSF) at pomace/MSF ratios of 1 : 1, 4 : 1, and 9 : 1 and with 5, 10, or 15% glycerol. The mixtures were compression‐molded at 130–140°C into biocomposite boards to evaluate their mechanical and thermal properties, water absorption and solubility, and microstructure. Among the three pomaces, the BP board was the stiffest, whereas the wine grape pomace board was the most flexible. The breaking strength and modulus of elasticity of the BP/MSF boards increased with increasing MSF concentration but decreased with increased glycerol concentration. Mixing the pomace and glycerol into SF shifted the endothermic peaks and initial degradation to lower temperatures compared to that of SF alone. Increasing the glycerol concentration decreased the water absorption but increased the water solubility of the BP/MSF board. The pomace/MSF ratio in the board did not affect (P > 0.05) the water absorption, but the water solubility increased with increasing pomace concentration. Glycerol addition in the BP/MSF board smoothed the fracture surface, as shown by scanning electron microscopy images. This study may provide an approach to reducing fruit pomace disposal through the development of new value‐added biodegradable products for industrial applications, such as nursery pots and egg cartons. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The structure of acidic surface oxides on carbon and graphite—II

Diazomethane has been used to methylate the “active” hydrogen associated with acidic oxides on carbon and graphite surfaces. Analysis of the methoxyl groups so formed showed that the active hydrogen was present as an OH group and that the total active hydrogen content of both carbon and graphite degassed at temperatures up to 800°C was very close to the uptake of 0.05 N sodium hydroxide. Studies on the carbon black Spheron 6 showed that the acidic oxide decomposing at about 250°C was not methylated by diazomethane but the group decomposing around 600°C was rapidly methylated. In addition a group decomposing at 400–500°C was found to be slowly methylated by diazomethane.     

Antioxidant activity of grape extracts in a lecithin liposome system

Extracts of 14 different grapes were tested for their antioxidant activities in a copper-catalyzed lecithin liposome oxidation assay and analyzed for their phenolic components by high-performance liquid chromatography (HPLC). The total phenolic contents of the grape extracts varied from 176 to 1236 mg gallic acid equivalents (GAE)/L. Extracts of red wine grape varieties contained higher concentrations of phenolics than other varieties. When compared at the same 20 μM GAE basis, the grape extracts inhibited formation of conjugated diene hydroperoxides by 25.1 to 67.9%, and hexanal formation by 49.3 to 97.8%. Extracts of red table grape varieties Red Globe and Emperor and white wine grape varieties Chardonnay and Sauvignon Blanc gave the highest antioxidant activities. The relative percentage inhibition of conjugated dienes and hexanal correlated with total phenols (r=0.86 and 0.89). HPLC analyses showed that anthocyanins were the most abundant phenolic compounds in extracts of red grapes, and flavonols were most abundant in extracts of white grapes.     

THERMODYNAMIC MODELS FOR WATER SORPTION BY GRAPE SKIN AND PULP

ABSTRACT

The enthalpy-entropy compensation theory was applied to water sorption for grapes of Italy variety. The moisture sorption isotherms were analyzed using the static gravimetric method at 35, 40, 50, 60, 70 and 75° C. For isotherms construction, the skin and pulp of the grape were used separately and it was possible to observe significant differences. The GAB equation was fitted to the experimental data, using direct nonlinear regression analysis; the agreement between experimental and calculated values was satisfactory. The net isosteric heat or enthalpy of water sorption, determined from the equilibrium sorption data, showed a different behavior when compared with other works, as it was obtained for skin and pulp separately. Plots of Ah vs AS for skin and pulp provided the isokinetic temperatures T_BS = 423.2 ± 27.6 K and T_BP = 424.5 ± 25.3 K, respectively, indicating an enthalpy-controlled desorption process over the whole range of moisture content considered.     

Content and diffusion of water and gases in MgAl2O4 spinel crystals synthesized to produce ceramics

Content, evolution and diffusion characteristics of water and gases in fine-crystalline spinel MgAl₂O₄ were studied by kinetic thermodesoption mass spectrometry. Water is the main volatile component by quantity in the spinel structure. From the spinel crystals with an average size of 0.52 μm, water is released in vacuum in three temperature ranges: at 100–200 °C due to desorption from micropores, at 300–600 °C due to near-surface dehydroxylation and at 500–800 °C due to diffusion of water from the crystal bulk. The content of structural water, diffusively released from the crystals, is about 3000 ppm. The coefficients and activation energy of diffusion of water from spinel crystals in the range 500–700 °C were calculated. This allows us to estimate at any temperature the degassing time of the spinel with a certain degree of dispersion and ceramics made of it, and thereby promote the production of high-quality ceramics.     

Transport number of charge-transfer complexes in solution

Iodine which is generally a non-conductor in non-polar solvents, conducts electricity in methanol, ethanol and water. The majority of the charge carriers in the solutions of charge-transfer complexes of methanol—iodine and ethanol—iodine are anion constituents (t^25°C_? are 0.739, 0.728 for 0.1 N solution of iodine in methanol and ethanol respectively) and for water—iodine it is cation constituents (t^25°C₊ is 0.905 for 0.0024 N iodine). The transport number of anion decreases with the increase in temperature whereas it increases with the increase in concentration at 25°C.     

Properties of coal tar characterized by slight pyrolysis

The behavior of coal tars with different levels of pyrolysis in thermal fractionation is compared in the laboratory. The properties and group composition of the nonboiling residues (medium-temperature pitch) obtained by the distillation of coal tars at different temperatures, in comparable conditions, is investigated. The results indicate that the distillation of tars characterized by slight pyrolysis is accompanied by vigorous destruction processes, also affecting the α₁ fraction (t = 335–350°C), with subsequent reactions among the destruction products, leading to active increase in the α₁ and α₂ fractions (t ≥ 350°C). This is a significant difference between tars characterized by light pyrolysis and considerable pyrolysis.     

Extraction of Total Phenolics of Sour Cherry Pomace by High Pressure Solvent and Subcritical Fluid and Determination of the Antioxidant Activities of the Extracts

Abstract

High pressure liquid extraction (HPE) and subcritical fluid (CO₂+ethanol) extraction (SCE) were used for the extraction of total phenolic compounds (TPC) from sour cherry pomace. Antiradical efficiency (AE) of the extracts was also determined. Ethanol was the solvent for HPE and co‐solvent for SCE. Combinations of pressure (50, 125, 200 MPa), temperature (20, 40, 60°C), solid/solvent ratio (0.05, 0.15, 0.25 g/ml) and extraction time (10, 25, 40 min) were variables for HPE according to the Box‐Behnken experimental design. The variables used for SCE were pressure (20, 40, 60 MPa), temperature (40, 50, 60°C), ethanol concentration (14, 17, 20 wt%) and extraction time (10, 25, 40 min). For HPE, TPC, and AE at the optimum conditions (176–193 MPa, 60°C, 0.06–0.07 g solid/ml solvent, 25 min) were found as 3.80 mg gae/g sample and 22 mg DPPH^?/g sample, respectively. TPC and AE at the optimum conditions (54.8–59 MPa, 50.6–54.4°C, 20 wt% ethanol, 40 min) for SCE were determined as 0.60 mg gae/g sample and 2.30 mg DPPH^?/g sample for sour cherry pomace, respectively.     

Effect of Pre-Melting Time on Crystallization of Poly(ethylene terephthalate)

In this study poly(ethylene terephthalate) (PET) was melted at 300°C, approximately 46°C above the crystalline melting point, T _m, for different times, i.e., Δt _m,=5, 8, and 10 min, and then quenched to different isothermal crystallization temperatures, T _c, ranging from 190°C to 230°C. The effect of pre-melting time, Δt _m, at 300°C on the degree of crystallinity and on crystalline morphology were investigated by differential scanning calorimetry (DSC) and polarized-light microscopy (PLM). After crystallization at low T _c, PLM data revealed the PET contained usual, positive, and unringed spherulites. After crystallization at high T _c PET contained unusual, ringed, and double-extinction spherulites. The experimental results reveal that increasing the pre-melting time Δt _m at 300°C causes an increment in T _c for usual–unusual, unringed–ringed, and positive–double-extinction transitions of the PET spherulites. The experimental results also show that PET with a pre-melting time Δt _m=8 min had higher crystallinity than those with pre-melting times Δt _m=5 and 10 min. These crystallization phenomena were attributed to the different numbers of residual unmelted PET crystallites as a result of the variation in pre-melting time, Δt _m, at 300°C.     

Characterization of cookies made with deseeded grape pomace

Characterization of cookies made with deseeded grape pomace. The objective of this study was to evaluate deseeded grape pomace as a potential ingredient to elaborate some food products. Cookies were made with flour containing four levels of deseeded grape pomace (0, 5, 7.5 and 10%). Moisture, protein, ashes, fat, tannins and dietary fiber contents were determined in both the deseeded of grape pomace and the cookies. Besides, color, sensorial acceptability and biological evaluations of Net Protein Ratio (NPR), Apparent Digestibility (AD) and True Digestibility (TD) of Protein were determined to the cookies. Substantial amounts of dietary fiber and ashes were found in both the deseeded grape pomace and the cookies. Total dietary fiber increased while adding more deseeded grape pomace. Cookies were well accepted as observed in the sensory evaluation, showing no significative differences among the four levels of deseeded grape pomace addition. The addition of deseeded grape pomace imparted a darker color to the cookies. The dark color was greater in the samples containing more fiber which was indicated by the lower L color value. Regarding nutritional analysis, the higher the deseeded grape pomace addition, the lower the NPR, AD, and TD values. The NPR was affected in greater degree, although these differences were not significant. It is possible to use deseeded grape pomace as an ingredient to make high fiber cookies with acceptable sensorial attributes.     

Facile corrosion synthesis and sintering of disperse pure tetragonal zirconia nanoparticles

Disperse pure tetragonal zirconia (t-ZrO₂) nanoparticles smaller than 10 nm are essential for preparation of structural and functional zirconia materials, but syntheses of t-ZrO₂ nanoparticles using inorganic zirconium salts usually result in severe agglomeration. In this paper, we report a hydrothermal corrosion approach for improving the dispersity of t-ZrO₂ nanoparticles synthesized by precipitation using zirconium oxychloride without any surfactants. Disperse pure t-ZrO₂ nanoparticles with average sizes of 4.5 and 6 nm and size distributions of 2–11 and 3–12 nm were obtained by calcining precipitates at 400 °C for 2 h and 500 °C for 0.5 h followed by HCl corrosion at 120 °C for 75 h, respectively. Disperse t-ZrO₂ nanoparticles with an average size of 6 nm and a size distribution of 3–12 nm were pressed into green compacts at 500 MPa and sintered by two-step sintering (heating to 1150 °C without hold and decreasing to 1000 °C with a 10 h hold). The sintered bodies are dense pure monoclinic ZrO₂ nanocrystalline ceramic with a relative density of 99.9% and an average grain size of 110 nm.     

Solutions of iodic acid in formamide. Thermodynamic properties from electromotive force measurements

Electromotive force measurements on cells without liquid junction have been used to determine pK_a of iodic acid and the standard electrode potentials (E°) of the silver-silver iodate electrode in formamide at 9 temperatures from 5–45°C. The pK_a was evaluated by using the Debye-Huckel theory with an ion-size parameter of 5.5 A°. The change in the standard electrode potentials is given as a function of temperature, t°C by the equation E°_t = 0.2786 - 8.125 x 10^?4(t - 25) - 6.385 x 10^?6(t - 25)² The standard thermodynamic quantities (ΔG°, ΔH°, and ΔS°) for the cell reactions have been evaluated for different temperatures.     

Effect of the Drying Process on the Intensification of Phenolic Compounds Recovery from Grape Pomace Using Accelerated Solvent Extraction

In light of their environmental and economic interests, food byproducts have been increasingly exploited and valorized for their richness in dietary fibers and antioxidants. Phenolic compounds are antioxidant bioactive molecules highly present in grape byproducts. Herein, the accelerated solvent extraction (ASE) of phenolic compounds from wet and dried grape pomace, at 45 °C, was conducted and the highest phenolic compounds yield (PCY) for wet (16.2 g GAE/100 g DM) and dry (7.28 g GAE/100 g DM) grape pomace extracts were obtained with 70% ethanol/water solvent at 140 °C. The PCY obtained from wet pomace was up to two times better compared to the dry byproduct and up to 15 times better compared to the same food matrices treated with conventional methods. With regard to Resveratrol, the corresponding dry pomace extract had a better free radical scavenging activity (49.12%) than the wet extract (39.8%). The drying pretreatment process seems to ameliorate the antiradical activity, especially when the extraction by ASE is performed at temperatures above 100 °C. HPLC-DAD analysis showed that the diversity of the flavonoid and the non-flavonoid compounds found in the extracts was seriously affected by the extraction temperature and the pretreatment of the raw material. This diversity seems to play a key role in the scavenging activity demonstrated by the extracts. Our results emphasize on ASE usage as a promising method for the preparation of highly concentrated and bioactive phenolic extracts that could be used in several industrial applications.     

Investigation of ferroelectric,piezoelectric and mechanically coupled properties of lead-free (Ba0.85Ca0.15) (Zr0.1Ti0.9)O3 ceramics

Lead-free piezoelectric ceramic (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT) has been synthesised by solid-state sintering method and the effect of grain size on ferroelectric, piezoelectric, dielectric, mechanical and piezo-electro-mechanical properties was systematically studied. The compacted powders were sintered at three temperatures i.e. 1450°°C, 1500°C and 1550°C for an optimised duration of 5?h and they have exhibited well resolved morphotropic phase boundary with an average grain size ranging from 10 to 25?µm. Enhanced piezoelectric charge, d₃₃ ～ 560 pC/N and voltage, g₃₃ ～ 14.3?mV?m/N coefficients were obtained for the 1450°C sintered BCZT sample. A maximum strain of around ～0.14% was obtained which is comparable to that of lead-based piezoelectrics. Variation of relative permittivity with temperature revealed that the curves are independent of frequency, indicating the typical relaxor ferroelectric nature of the samples. A systematic study on cyclic loading was performed to evaluate piezo-electro-mechanical coefficients at different loads which showed hysteresis behaviour. High value of elastic modulus (E) and hardness (H) i.e. 262.7?±?38.1?GPa and 13.7?±?1.7?GPa were exhibited by samples sintered at 1450°C, which is higher than that of BCZT synthesised by wet-chemical methods. The results are discussed.