Design and characterization of modified urethane lacquer coating

A new series of natural lacquer/polyurethane (LPU) blended films were synthesized. The new lacquer/polyurethane films have very good visual color and detected gloss, fast drying time, strong weather resistance, especially against UV light and water, and a better pencil lead hardness (8H). The gel ratio increases with drying time and becomes stable after 6 months (more than 99%). The surface glass transition temperature (T_gs) obtained from a rigid-body pendulum physical properties testing (RPT) instrument showed that the new LPU films dried for 6 months have higher T_gs than polyurethane (PU) films in the following order: LPU 100 > LPU 90 > LPU 80 > LPU 70 > LPU 60 > LPU 50 > PU. Differential scanning calorimeter (DSC) results showed the same tendency as T_g but without a great gap in the LPU series except for polyurethane. Thermogravimetric analysis (TGA) showed that when the ratio of natural lacquer is more than 50%, the 50% weight loss temperatures increase about 100 °C. In addition, the reaction between lacquer and polyurethane is discussed based on the IR and NMR measurements.     

Effect of different drying conditions on the vitamin C (ascorbic acid) content of Hayward kiwifruits (Actinidia deliciosa Planch)

In this study, drying kinetics of kiwifruit are investigated experimentally and theoretically under varying drying conditions. Experiments are conducted using air temperatures at 35, 45, 55 and 65 °C, mean velocities at 0.3, 0.6 and 0.9 m s^?1 and, relative humidity values at 40%, 55%, 70% and 85%. Initially, sorption isotherms of the dried kiwifruit slices are determined for different temperatures and equilibrium relative humidity values. The values of the moisture diffusivity, D_eff are obtained from the Fick's diffusion model. The effects of the governing drying parameters on the vitamin C content as well as on the total drying time are determined. The experimental moisture data were fitted to some models available in the literature, mainly the Henderson and Pabis model, the Lewis model and the two-term exponential model and, a good agreement was observed. In addition, it is disclosed that increasing drying air temperature causes more loss in vitamin C in the dried fruits while degradation of vitamin C is reduced with increasing relative humidity of drying air.     

Effect of temperature on structural properties of Aloe vera (Aloe barbadensis Miller) gel and Weibull distribution for modelling drying process

Aloe vera (Aloe barbadensis Miller) gel was dried at five inlet temperatures 50, 60, 70, 80 and 90 °C, in a convective dryer with a constant air flow of 2.0 ± 0.2 m/s. Rehydration ratio, water holding capacity, texture, microstructure and total polysaccharide content were evaluated. Drying kinetics was estimated using the Weibull distribution (r² > 0.97 and Chi-square < 0.0009). Values of scale and shape parameters ranged from 90.94 to 341.06 (min) and 1.43 to 1.49, respectively. Furthermore, the influence of temperature on the model parameters as well as on the quality attributes was analysed using a least significant difference test (p-value < 0.05). These effects were more evident for the long drying period (e.g. 810 min at 50 °C). However, minor alterations in the structural properties and total polysaccharide content were produced at drying temperatures of 60–70 °C, resulting in a high quality gel.     

Usage of solar-assisted spouted bed drier in drying of pea

The main objective of this study is to evaluate the effects of solar-assisted spouted bed and open sun drying on the drying rate and quality parameters of pea. Color, shrinkage, bulk and apparent densities, internal and bulk porosities, rehydration capacity and microstructure were the quality parameters investigated in dried product.Drying rate for solar-assisted spouted bed was about 3.5 times of drying rate for open sun drying. Air temperature changed between 20 °C and 27.4 °C during open sun drying while temperature of air at the inlet of solar-assisted spouted bed dryer varied between 35.3 °C and 65.5 °C during the experiments. Effective diffusivities were found to be 0.64 × 10^?10 and 3.27 × 10^?10 m²/s for open sun and solar-assisted spouted bed drying of pea, respectively. In color analysis, it was observed that a* value increased while b* value decreased for both drying methods. Bulk density and apparent density of peas dried under open sun was higher than that in solar-assisted spouted bed drier. In both drying methods, internal and bulk porosities decreased. Shrinkage was more for open sun dried samples. Rehydration capacity for solar-assisted spouted bed dried sample was higher than the one for open sun dried.     

Quality evaluation of pineapple fruit during drying process

Pineapple (Anana comosus) slices were dried by hot-air convective drying technique at fixed temperature (45, 60 and 75 °C) and constant air velocity of 1.5 m/s. The effect of drying conditions (drying time and air temperature) on the pineapple quality was evaluated. The quality of dehydrated pineapple was analyzed by color and texture changes, l-ascorbic acid loss and the ability of water uptake during rehydration procedure. Water uptake during rehydration was described by Page model. Statistical analysis of data revealed not significant difference (p > 0.05) among color and mechanical characteristics of pineapple samples dried at different drying temperatures to preset moisture content. Pineapple samples dried at 45 °C had better rehydration ability and more l-ascorbic acid retention than those obtained by air drying 75 °C. Hence, 45 °C drying temperature was best condition for pineapple quality preservation.     

Application of hydrophilic ionic liquid treatment to the morphological observations of hydrated porous ceramic green bodies

In this study, a simple and convenient method for observing the surface morphology of hydrated porous ceramic green bodies is proposed. The porous hyrdoxyapatite (HAp) green body was prepared by a gelcasting process and was dried in a humid chamber from 90 to 50% relative humidity at 25 °C before subsequent treatment with a hydrophilic ionic liquid (IL). The surface morphology of the IL-treated porous HAp green body was observed using FE-SEM. The results showed that the pore morphology and microstructure of the HAp green body was readily observable without evidence of charging. The as-prepared sample showed pores approximately 300–600 μm in diameter, which gradually contracted to approximately 200–400 μm upon drying in the humid chamber. Following sintering at 1000 °C, the pores had further contracted to approximately 100–300 μm. The IL binds with the surrounding water to prevent the sample from drying in vacuum and acts as a conductive media, allowing the HAp ceramics to be observed in the electron microscope. In comparison to the micro-focused X-ray CT analysis, the fine pore structure (less than 100 μm) could only be observed using FE-SEM when the porous body had also been subjected to the IL treatment.     

The energy consumption and color analysis of freeze/microwave freeze banana chips

This study investigated the energy consumption of preparing banana chips by freeze drying (FD) and microwave freeze drying (MFD) methods. The results in this study showed that the energy consumption for 400 g fresh banana (about 95 g dried samples) by FD process and MFD process are about 35.73 × 10⁶ J (9.92 kW h) and 21.76 × 10⁶ J (6.57 kW h), respectively. Compared to the traditional FD process, MFD can save up to 35.7% energy and 40% drying time. Increasing the heating power in the secondary drying stage of MFD process had been confirmed to result in decrease in both the energy consumption and drying time. After increasing the microwave power in the secondary drying stage from 1.0 W/g to 1.5 W/g in MFD process, total energy consumption is about 18.12 × 10⁶ J (5.56 kW h) and drying time can be reduced from 360 min to 270 min. The sensory evaluation of produced banana chips at different drying conditions (1.0 W/g, 1.5 W/g and 2.0 W/g) revealed that the sensory properties are acceptable by the customers except the 2 W/g microwave power dried product. Thus, the method that increased the heating powder in the secondary drying stage of the MFD process could potentially be an effective method to reduce the energy consumption without seriously sacrificing the color of the end product.     

Effect of drying methods on volatiles of Chinese ginger (Zingiber officinale Roscoe)

Fresh ginger slices were dehydrated by air drying (AD), microwave drying (MD), vacuum drying (VD), and freezing drying (FD). Volatiles were extracted from fresh ginger pulp and dried ground ginger powder with solid-phase microextraction (SPME), and identified by gas chromatography–mass spectrometry (GC–MS). Results indicated that, 19, 28, 21, 20, 31 and 20 novel compounds (70 in total) appeared in dried gingers treated by AD at 50, 60 and 70 °C, MD at 60 W, VD in 13.3 kPa at 60 °C and FD in 0.203 kPa at chamber temperature of 22 °C, respectively. Principal component analysis for the main volatiles indicated that drying increased the relative contents of benzene,1-(1,5-dimethyl-4-hexenyl)-4-methyl-, 1,3-cyclohexadiene,5-(1,5-dimethyl-4-hexenyl)-2-methyl-,[S-(R*,S*)]-, α-farnesene and cyclohexene,3-(1,5-dimethyl-4-hexenyl) -6-methylene-,[S-(R*,S*)]- while decreased those of 2,6-octadienal,3,7-dimethyl-,(Z) and 2,6-octadienal,3,7-dimethyl-. Cluster analysis disclosed that MD was the most favorite drying way, followed by AD at 60 °C, VD, FD, and AD at 50 and 70 °C.     

Thin layer solar drying characteristics of silkworm pupae

Thin layer solar drying experiments of silkworm pupae using a solar tunnel dryer were conducted under the tropical weather conditions of Mahasarakham, Thailand. The dryer consisted of a transparent glass covered flat-plate collector and a drying tunnel connected in series to supply hot air directly into the drying tunnel using a blower. During the experiments, silkworm pupae were dried to the final moisture content of 0.15 kg water kg^?1 dry matter from 4.37 kg water kg^?1 dry matter in 373 min at the corresponding air flow rate of 0.32 kg s^?1. Ten different thin layer drying models were compared according to their coefficient of determination to estimate drying curves. The Midilli–Kucuk model precisely represents the solar tunnel drying behavior with the coefficient of determination (R²) of 0.9982. The maximum drying rate and effective moisture diffusivity were 0.6723 kg water kg^?1 dry matter h^?1 and 2.7696 × 10^?10 m² s^?1, respectively, on the drying air flow rate of 0.32 kg s^?1. A quality assessment shows that the lipid content of the dried silkworm pupae was not affected by the solar tunnel dryer. A slight decrease of polyunsaturated fatty acid (PUFA) was observed.     

Changes in physico-chemical and functional properties during convective drying of aloe vera (Aloe barbadensis) leaves

Aloe vera leaves were dried at different temperatures in hot air oven and powdered. The percent powder yield was found 2.60%, 2.60%, 2.55% and 2.52% at 50, 60, 70 and 80 °C respectively. Powder samples had the pH (1% solution) 3.51, 3.53, 3.52 and 3.53 with the rise of drying temperature in the selected range. Statistically, yield and pH indicated no significant difference (p < 0.5) due to drying temperature variation. Wettability of powder at 70 °C was 32 s as compared to 35, 35 and 37 s in the samples obtained at 50, 60 and 80 °C respectively. Water absorption capacity of powder at 70 °C was 359% as compare to 351%, 354% and 356% of 50, 60, and 80 °C powder samples. The HPLC chromatogram obtained for the sample dried at 80 °C shows that as the temperature increased from 50 to 80 °C, aloin content decreased from 10.6 to 1.7 ppm. The “a” values were found 2.028, 2.226, ?0.282 and 2.531 for the samples obtained after drying at 50, 60, 70 and 80 °C respectively. Samples obtained at 70 °C showed negative “a” value indicated that the sample was more greenish in colour as compared to other samples.     

Recovery of water-soluble compounds from Ganoderma lucidum by hydrothermal treatment

The polypore fungus Ganoderma lucidum provides bioactive compounds containing several triterpenoids and polysaccharides that are reported to posses anti-cancerous and immunomodulatory properties. In this study, we determined the optimal conditions for extracting water-soluble polysaccharide compounds present in the ground form (3-mm particle size) of G. lucidum using water in subcritical conditions at distinct temperatures by two methods: batch-type subcritical water extraction and semi-continuous-type extraction. The optimal condition where solubility is higher to recover the maximum total amount of β-glucan from G. lucidum (0.44 mg/100 g dried sample) was determined to be 473 K at 10 MPa, with a water flow rate of 1 ml/min for 130 min. For batch-type and semi-continuous-type extractions, the best solubility was obtained at 473 K having efficiencies of 78.1% and 57.4%, and the highest extracted amounts of total WSOC were 328 and 241 mg WSOC/g dry sample, respectively.     

Separation of CNF agglomerates from a ceramic suspension by spray drying technique

Aqueous silicon nitride based composite suspensions with the addition of 3.1 wt% of carbon nano-fibers (CNFs) were dried using two different drying techniques: spray drying and freeze drying. The paper deals with optimisation of parameters of the spray drying processwith the aim of maximising the yield and improve the quality of the granulate. Freeze drying was selected as a reference drying method, because no powder separation can occur in the course of the process. Prepared suspensions were spray dried at 4 different temperatures: 80, 110, 140 and 180 °C. After each run, two types of granules were obtained: from the separation flask and from the product vessel. Thermo-gravimetric analysis together with SEM examination show that spray drying results in separation of CNFs agglomerates. The granules from separation flask are always enriched by CNFs agglomerates whilst the granules from product vessel have reduced content of CNFs agglomerates. Sintering of spray-dried granules from the product vessel resulted in the composite with uniform microstructure, low amount of CNFs agglomerates and high relative density.     

Effect of drying temperatures on starch-related functional and thermal properties of chestnut flours

The use of starchy flours in food systems greatly depends on the related functional properties of starch. The effect of drying temperatures on starch-related functional properties of flours obtained from fruits of the two most common Portuguese Castanea sativa varieties (Martainha and Longal) was evaluated. Flours were analysed for amylose and resistant starch contents, swelling ability, pasting properties and thermal characteristics. Drying temperature is positively correlated with amylose content, resistant starch and viscoamylographic properties, mainly the temperatures higher than 40 °C. Amylograms of fruits dried at 60 °C displayed higher peak viscosity (1370 B.U. and 2260 B.U. respectively for Longal and Martainha) when compared to the other temperatures tested (40 °C, 50 °C and 70 °C). Decreases in transition temperatures and in enthalpy evaluated by thermal analysis were observed with increasing drying temperatures, suggesting modifications in starch structure during the drying process. The effects of drying temperatures were more evident in Longal variety. The flours from the two chestnut varieties and from fruits dried at low temperatures and fruits dried at high temperature showed significant differences between the evaluated properties.     

Optical and mechanical properties of cocona chips as affected by the drying process

The effect of the application of a pre-osmotic treatment to obtain hot air dried cocona (Solanum sessiliofurum Dunal) chips was studied. The drying kinetics and the optical and mechanical properties of cocona chips obtained by the combined method of osmotic dehydration and hot air drying (OD + HAD) and by only hot air drying (HAD) were compared. Samples were dried by hot air at 60 °C. For the combined method, they were pre-dried to a moisture content of 75 g_water/100 g, immersed in a 55 °Brix sucrose solution at 25 °C for 48 min. The pre-osmodehydration applied did not influence the subsequent hot air drying kinetics, resulting in a final product with 0.055 ± 0.005 g_water/g_cocona. The optical properties of OD + HAD chips were more favorable, exhibiting a smaller color change with respect to the fresh fruit (±15 units) than the HAD samples (±23 units). On the other hand, the OD + HAD chips presented more fracture peaks than HAD ones, this related with a structure with a higher degree of crispness, a very desirable property for a chip product.     

Shape forming alumina slurries via Colloidal IsoPressing

The relative density, deformation behavior, and dynamic rheology of bodies consolidated from aqueous alumina slurries, formulated at pH 4 and containing NH₄Cl, were studied as a function of the salt concentration (0.1–0.75 M). The smallest salt concentration produced the highest relative density (0.596), which was independent of consolidation pressure. Nearly identical relative densities were obtained for the other salt concentrations, ranging from 0.57 to 0.59 for consolidation pressures of 5–100 MPa, respectively. The consolidated bodies exhibited either a plastic or an elastic behavior when tested in compression. It was observed that the transition from a plastic to an elastic behavior occurred at a critical consolidation pressure. This critical consolidation pressure was directly dependent on the salt concentration. The storage (elastic) modulus for the fluidized, plastic bodies increased with salt concentration. The storage modulus was also observed to be dependent on the time the bodies were allowed to rest after they were subjected to a high shear rate. A pre-consolidated and fluidized slurry formulated to contain 0.5 NH₄Cl was extruded into a rubber mold cavity and further consolidated by isopressing at 200 MPa for 2 min. The body not only increased its relative density (0.58–0.62), but it also became elastic to enable its removal from the rubber cavity without shape distortion. No linear shrinkage was detected after the isopressed bodies were dried. Because of the lack of shrinkage, rapid drying was possible. For example, bar specimens (6.4 mm × 12.7 mm × 60 mm) would survive a 34 °C/min heating rate to 300 °C; the specimen was completely dried within 20 min. Because shrinkage does not occur during drying, bodies could be placed directly into a furnace and heated to 1500 °C for 0.5 h to achieve a relative density of >0.99 and an average grain size of 1.6 μm.     

Effects of ultrasound on glass transition temperature of freeze-dried pear (Pyrus pyrifolia) using DMA thermal analysis

The effect of ultrasound pretreatment at various power (360 W, 600 W and 960 W, frequency 20 kHz) on the glass transition temperature of freeze dried pear (Pyrus pyrifolia) has been studied. DMA temperature plots were divided into four sections (A – glassy region, B – transition region, C – Rubbery plateau region and D – terminal region) with the aim to analyze their properties changed with sonication. Under the same freeze drying condition, with the increase in ultrasonic power, dried pear showed higher glass transition in terms of storage modulus, loss modulus and loss tangent peak. Also a decrease in a_w (0.31–0.23) and in moisture content (0.12–0.08 g/g d.b.) has been observed. Samples pretreated with ultrasound showed a better texture profile and much porous structure compared to control one. The results from the study indicated that, ultrasound pretreatment prior to freeze drying can improve the stability during storage of freeze dried pear.     

Infrared assisted dry-blanching and hybrid drying of carrot

Infrared (IR) blanching and IR assisted hot air (hybrid) drying of carrot slices were attempted and their performance (processing time, retention of vitamin C and rehydration characteristics) was compared with conventional blanching and drying techniques. Intermittent heating of carrot slices using IR radiation (chamber maintained at 180–240 °C) for 8–15 min resulted in desired level of enzyme inactivation. The time required for blanching of carrot slices (10 mm thick) using hot water, steam and IR radiation was 5, 3 and 15 min, respectively. Retention of water soluble vitamin C was higher (62%) in IR blanched carrot as compared to water (43%) and steam (49%) blanching. IR blanching reduced the moisture content by 13–23% (absolute). IR blanched samples dried by hybrid mode took ～45% lesser time compared to water blanched–hot air dried samples. Higher rehydration moisture of dried samples indicated the retention of cell structure during IR blanching. Vitamin C retention was ～39% higher in IR blanched–hybrid dried slices compared to water blanched–hot air dried. The study shows the potential application of dry-blanching and IR assisted hybrid drying in food processing for improving product quality.     

Power Ultrasound Mass Transfer Enhancement in Food Drying

Power ultrasound application could constitute a way to enhance food drying in order to improve not only mass transfer but also product quality, since it does not significantly heat the material. The main aim of this work was to assess the influence of power ultrasound on the mass transfer process during drying of different products, carrot, persimmon and lemon peel.Convective drying kinetics were carried out with ultrasound (US experiments 21.8 kHz, 75 W), or without ultrasound application (AIR experiments) at air velocities ranging between 0.5–12 m s⁻¹. Different geometries were used for each of the products: cubes in carrots (2 L = 8.5 mm), cylinders in persimmon (2 L = 30 mm and 2 R = 13 mm) and slabs in lemon peel (L = 10 mm). Drying kinetics were modelled by considering different diffusion models according to the geometry.The results show that air velocity and raw material characteristics play a role in convective drying kinetics assisted by power ultrasound. Power ultrasound increased effective moisture diffusivity at low air velocities for all the products. However, in the case of lemon peel, ultrasound also improved the drying rate at high air velocities. This behaviour may be explained by the disruption of the acoustic field at high air flow rates and the different level of intensity required due to the structure of the products. Therefore, the raw material constitutes an important variable to establish the influence of power ultrasound on convective drying.     

A cathodoluminescence study of boron doped {111}-homoepitaxial diamond films

In this work we use cathodoluminescence (CL) at liquid helium temperature to investigate the boron incorporation in {111}-homoepitaxial diamond films, grown outside the visible plasma ball by the Microwave plasma-assisted chemical vapor deposition (MPCVD) technique. The boron concentration of this set of films covers the whole possible doping range divided into four parts: Low doping (5 × 10¹⁶ < [B] < 1.5 × 10¹⁹ cm^? 3), high doping (1.5 × 10¹⁹ < [B] < 3 × 10²⁰ cm^? 3), heavy doping (3 × 10²⁰ < [B] < 2 × 10²¹ cm^? 3), and phase separation range ([B] > 2 × 10²¹ cm^? 3). The phase separation occurs for very high boron concentrations, between the diamond phase (sp³ carbon) and the other components of the layer, namely sp² carbon and boron. A part of them is accumulated outside the diamond lattice.This detailed cathodoluminescence investigation of {111}-homoepitaxial diamond films has led to determining the doping range of the films and following the evolution of their crystalline quality when the boron concentration increases. In addition, a comparison between {111} and {100} films in the same doping ranges has been undertaken.     

Free volume and permeabilities of O2 and H2 in Nafion membranes for polymer electrolyte fuel cells

The mechanism of gas permeation in Nafion membranes for polymer electrolyte fuel cells has been investigated from the viewpoint of free volume. Three different samples, a membrane with ionic exchange capacity (IEC) = 0.92 meq/g, and recast samples with IEC = 0.92 and 1.00 meq/g were used after drying. Free volume was quantified using the positron annihilation lifetime (PAL) technique and gas permeabilities were measured for O₂ and H₂ as functions of temperature and relative humidity. Good linear correlations between the logarithm of the permeabilities at different temperatures and reciprocal free volume indicate that gas permeation in dry Nafion is governed by the free volume. Nevertheless permeabilities are much smaller than the corresponding flexible chain polymer with a similar free volume size due to stiff chains of the perfluoroethylene backbone. In highly hydrated Nafion above 60% relative humidity, where the O₂ permeability varies oppositely to the free volume, gas permeation proved to be controlled by the gradual increase in overall flexibility of the Nafion–water system.