Dehydration Time Research Articles

Corneal stromal dehydration and optimal stromal exposure time during corneal refractive surgery measured using a three-dimensional optical profiler.

To quantitatively analyze human corneal stromal dehydration and estimate proper corneal stromal exposure time during corneal refractive surgery. The central thickness changes over time in 34 pieces of human corneal tissue were measured using a white light interferometer. The corneal stromal tissue was obtained by femtosecond laser small incision lenticule extraction. The thickness-time dehydration fitting curves were drawn, and the determination coefficient R2 was calculated. The differences in the fitting curve equation coefficients were compared between the thin and thick lenticule groups. The optimal stromal exposure time was calculated under various conditions, including different optical zones and allowable refractive errors. A water loss variation model was successfully established. Linear and quadratic fitting curves were drawn, and the determination coefficient R2 values were significantly close to 1. The average values of R2 for quadratic curves and linear phases 1, 2, and 3 were 0.998 ± 0.002, 0.995 ± 0.007, 0.996 ± 0.003, and 0.984 ± 0.035, respectively. The optimal stromal exposure time varied under different optical zones and allowable diopter error conditions. Taking the allowable error of 0.50 D and the optical zone size of 6.5mm as an example, the optimal time was approximately 24s. The dehydration rate of the human corneal stroma is nonlinear, and the quadratic stromal thickness-time dehydration fitting curve is more in line with the actual water loss trend. The length of the stroma exposure time may affect the postoperative refractive accuracy after corneal refractive surgery.

Cinética de secagem em camada de espuma da polpa mista de jambolão e acerola

ABSTRACT Acerola and jambolan are fruits with several bioactive compounds of phenolic origin and a product made with these two raw materials appears to be a food with high antioxidant and nutraceutical potential. Therefore, this study aimed to evaluate the foam mat drying of the mixed pulp of jambolan and acerola. Mixed pulp formulations, containing 1.0% albumin with 0.5% xanthan gum (F1), 0.5% carboxymethylcellulose (F2) and 0.5% guar gum (F3), were dehydrated at 50, 60, 70 and 80 °C, with foam mat thickness of 0.5 cm. The elevation of the drying temperature decreased the water content and dehydration time of the samples. Formulation F3 obtained the shortest drying times; all drying models resulted in good adjustments, especially Midilli. Formulation F3 obtained greater effective diffusivity; the activation energy was higher in the F1 combination. The samples with albumin-guar (F3) showed greater enthalpy and entropy and samples with albumin-xanthan gum (F1) showed the highest Gibbs free energy. Foam mat drying is an efficient way of preserving the jambolan and acerola mixed pulp.

Study on Pore Structure and Mechanical Property of Expansive Soil under Different Dehydration Conditions

To study the influence of dehydration conditions on the pore structure and the mechanical property of expansive soil, two experimental conditions with high-temperature drying (temperature 50 °C-humidity 10%) and high-temperature humid (temperature 50 °C-humidity 70%) were carried out. Taking the remolded expansive soil in the province of Anhui in China as the research object, this paper used mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) to analyze the pore size distribution and pore structure of remolded expansive soil samples under different dehydration conditions and duration. After these tests, their mechanical properties were further obtained by uniaxial compression tests. The results showed that the distribution of pore structure of expansive soil was various under different dehydration conditions. Under high temperature and dry environment, the volume of large pores decreased first and then increased with the time of dehydration, while the medium pore volume decreased until the dehydration was stable. Under high temperature and humid environment, the volume of large pore and medium pore both showed a trend of decrease until the dehydration kept stable. The pore volume of expansive soil did not change significantly under the two dehydration conditions. The uniaxial compressive strength (UCS) of remolded expansive soil samples in high temperature and dry environment reached the highest on the 5th day of dehydration, and then the soil strength decreased slightly until it stabilized. The UCS of remolded expansive soil reached the highest on the 15th day of dehydration under high temperature and humidity environment, and the soil strength changed little after continual dehydration. These tests showed that the UCS of dehydrated expansive soil samples under the condition of high temperature and humidity is higher than that of dehydrated expansive soil samples under the condition of high temperature and dry environment.

The Prediction of Drying Performance of Banana Rings Dried By Osmo-solar Dehydration Method

Solar drying is known as the oldest and most common traditional food preservation method. However, if the product is indirectly contacted with the sun light, there is negative effect in the color and nutrient values of the product. Solar dryers have been developed to utilize the heat effect of the sun to solve these problems. It can be used in combination with osmotic dehydration to increase the efficiency of the solar drying process. Osmotic dehydration is applied as a pretreatment technique in the drying process. The pretreatments to be applied before drying have important effects on the quality and operating cost of the product to be dried. In addition, the osmotic dehydration pretreatment enables to shorten the drying time and increase the drying potential. In this study, bananas with high drying temperature and high moisture content were sliced into 3 mm rings, then osmotic dehydration pre-drying was applied, and then they were dried in a solar tray dryer. Sucrose and citric acid solution in 2.5%, 5%, 7.5% and 10% (w/v) concentrations were used for osmotic dehydration treatment. In addition, samples without osmotic dehydration were dried in a solar dryer to determine the effect of pretreatment. The input variables of the drying process are solution concentration (0%, 2.5%, 5%, 7.5% and 10%), type of solution (sucrose solution and citric acid solution), osmotic dehydration time (10, 30, 60 and 90 min) and sun drying time (60, 120, 180, 240 and 300 min). Output variables were chosen as moisture ratio and shrinkage rate. The results clearly showed that both the moisture ratio and the shrinkage ratio have increased due to increased solar dryer time, solution concentration and immerse time. Osmotic dehydration was found to be effective in dried banana rings in the solar tray dryer. Gradient Boosting Machine (GBM) was used to model the drying conditions and the model was successful. The correlation coefficient (R2) values of the GBM model were respectively found as 0.94 and 0.83 for the moisture ratio and the shrinkage ratio.

Influence of Dehydration Temperature and Time on Physicochemical Properties of Tomato (Solanum lycopersicum L.) Powder

The purpose of this research was to determine the optimum dehydration temperature and time length for a better physicochemical quality of tomato powders. The treatments consisted of 70, 80 and 90°C dehydration temperatures and 9, 11, and 13 h time durations arranged in a completely randomized design (CRD) with triplicates. The inlet and outlet air temperatures of the hot air oven dryer were about 24 and 60°C respectively with an air velocity of about 2.9 m/s. Fresh tomatoes were used as a control. It has been observed that the major quality parameters of tomato powders were significantly increased with increasing dehydration temperature and time up to 80°C and 11 h respectively. When the dehydration temperature and time length went beyond 80°C and 11 h respectively, the quality of tomato powders declined. The maximum TSS content (7.433 °Brix), titratable acidity (0.4967), rehydration ratio (3.437), lycopene content (0.4512 mg/100 g) and lower pH value (4.433) were obtained at 80°C temperature and 11 h dehydration time. Moisture content was reduced to 11% at the same dehydration temperature and time length without considerable physiochemical quality loss. Inversely, vitamin C was reduced as dehydration temperature and time increased. Generally, the results of this study showed that dehydration of tomatoes with 80°C and 11 h temperature and time length respectively, provides better physicochemical quality of tomato powders. Future research is suggested on consumers' acceptance of dehydrated tomato powders.

Dehydration Time Effect on Tooth Color Measurement: An In Vitro Study.

Esthetics have become a primary influencing factor for patient satisfaction, thus dental restorations shade selection is critical, as it should closely resemble a healthy tooth. During various dental procedures, teeth are subjected to dehydration. The commonly used shade guides are being replaced with electronic color measurement devices for more precise measurements. The aim of this study was to evaluate the effect of dehydration time on tooth color measurement using a spectrophotometer. Study sample is represented by 20 extracted caries-free maxillary central incisors, which were obtained from several private clinics in Riyadh, Saudi Arabia, and soaked in normal saline for 24 hours. The VITA Easyshade Advance 4.0 spectrophotometer was used to measure the color at different areas of the tooth (cervical, middle, and incisal thirds) at three time intervals (baseline, after 1 hour of dehydration, and after 2 hours of dehydration). All color coordinates across the different areas of each tooth at the incisal, middle, and cervical thirds descriptive statistics of mean (standard deviation) values were calculated and were compared at the different time intervals at baseline, after 1 hour of dehydration, and after 2 hours of dehydration. Finally, the color change value ∆E was calculated using the formula ∆E*ab = √ (L2∗ - L1∗)2 + (a2∗ - a1∗)2 + (b2∗ - b1∗)2. The color difference ∆E showed statistically significant changes at different time intervals: at baseline, after 1 hour of dehydration, and after 2 hours of dehydration (p < 0.001). Hue had statistically significant changes between 1 hour and 2 hours of dehydration (p = 0.002). Chroma value also showed statistically significant changes (p < 0.001) in all time intervals. By using VITA Easyshade Advance 4.0 spectrophotometer, it was indicated that the tooth color measurements were significantly affected by dehydration time, and tooth shade appeared lighter due to changes in the refractive indices as air replaces the interprism spaces within the enamel. Tooth color measurements for shade selection should be taken as soon as possible to limit dehydration effect and ensure a more accurate shade selection for an enhanced esthetic result.

Effect of dehydration time and air tightness on pore distribution of potassium and metakaolin-based geopolymer

As a catalyst support in the nuclear waste containers in the Fukushima Daiichi Nuclear Power Station, geopolymer is required to show high strength, high porosity and durability. The aim of this study is to evaluate the mechanical properties and pore size distribution of hardened samples based on two test variables, which include early-age dehydration time and air tightness. The early-age dehydration time ranges from 1–4 d, and air tightness is implemented using the two methods of total sealing and air contact. However, the average pore size was around 2.0 × 102 μm, the Vickers hardness was around 90 MPa, and the relative weight change on the 14th day was within 10% for all the samples that were not affected by the curing time and air tightness. It can be inferred that the pores of the sample may have been formed within a day and may not be affected by the curing time.

Modeling convective thin-layer drying of carrot slices and quality parameters

The influence of thin layer convective dehydration parameters on drying kinetics parameters, chemical composition, and color parameters of carrot slices were investigated, and corresponding mathematical models were developed. In the carrot slices, convective dehydration process hot air temperature and the sample slice thickness were varied, while measured, calculated, and modeled responses were: time of dehydration, effective moisture diffusivity, the energy of activation, proteins and cellulose contents, lightness, redness, and yellowness. The obtained results showed that varied convective dehydration process parameters statistically significantly affected all investigated responses except activation energy. The most efficient drying model with the minimum thickness (3 mm) and the maximum drying temperature (70?C) had the shortest drying time (231 minutes). This model had the minimum resistance to mass transfer (the minimum effective moisture diffusivity, 2.04 ? 10?08 ? 7.12 ? 10?08 [m2s?1]), and the average maximum energy of activation (31.31 kJ/mol). As far as the carrot slices? chemical composition and color parameters were concerned, the model with the maximum thickness (9 mm) and the minimum drying temperature (35?C) was the optimal one. This model had the longest dehydration time (934 minutes), the maximum resistance to the mass transfer (8.87 ? 10?08 [m2s?1]), the minimum total protein content (5.26 %), and the darkest color (49.70). The highest protein content (7.91%) was found for the samples subjected to the highest drying temperatures and the lowest carrot slice thickness. In contrast, the process of convective dehydration had led to the lighter, reddish, and yellowish carrot slices. All developed mathematical models were statistically significant.

Comparison of dehydration methods for untreated lignin resole by hot air oven and vacuum rotary evaporator to synthesize lignin-based phenolic foam

We investigate two different dehydration methods to determine their suitability for preparing resoles for foam synthesis. A simplified process for synthesizing lignin foam (LF) from lignin resole (LR) dehydrated in a hot air oven (HAO) is compared with that dehydrated using a vacuum rotary evaporator (VRE). First, the LR formulation is prepared by mixing phenol with untreated lignin (0%–15% by weight), and subsequently, the prepared LRs are dehydrated using an HAO and a VRE. We find that for the same dehydration time, both techniques yield LRs with the same chemical compositions; however, the HAO technique affords a moisture removal of 13–17% by weight, whereas the VRE technique removes 9–12% moisture by weight. The LR obtained by the HAO is more viscous and maintains a circular shape after being dropped on a plate. In our experimental synthesis of LF containing VRE resole, biofoam is not formed owing to insufficient viscosity, whereas biofoam is obtained with the HAO resole. The synthesized LF exhibits a density range of 44.96–85.68 kg/m3 and a compressive strength of 103.28–152.27 kPa. Scanning electron microscopy investigations show that the morphology of the foam is a closed-cell structure. The simplified synthesis of LF from the HAO-treated resole offers significant advantages over the complexity of the conventional VRE approach in terms of equipment cost and energy consumption. The resulting foam exhibits a thermal stability and thermal performance comparable with the counterpart properties of phenolic foam.

AN OPERATIONAL EVALUATION OF A TECHNOLOGICAL LINE FOR INDUSTRIAL DRIED CHERRY PRODUCTION BY THE OSMOTIC-CONVECTION METHOD, COMPARED TO A LABORATORY SCALE

Background. Pre-osmotic dehydration of fruits may significantly reduce free water content. It also causes fruit penetration by solution components, increasing the efficiency of products manufactured by the osmotic-convection method. A study was carried out on a laboratory and industrial scale to perform an operational evaluation of a technological line for dried cherry production. Frozen pitted cherries (Łutówka variety) were the research material. Sucrose solution, concentrated apple juice, and sucrose and glucosefructose syrup mixture (1:1) were used for OD; with 70±2 °Brix at 40, 55 °C (an industrial scale), and 50 °C (a laboratory scale) to obtain ≥ 60 °Brix of fruit extract. Industrial convection drying was carried out at 70 °C until the water activity of &lt; 0.6 was reached. Results and conclusion. Increasing the osmoactive solution temperature enhanced the efficiency of a process aimed at fruit saturation by an osmotic substance and shortened the treatment time. Higher dehydration efficiency resulted in shorter convective drying time. No impact of the osmotic solution type on most mass exchange indices in dehydrated fruits was found. Despite the significantly higher process efficiency of the pre-dehydration in apple juice concentrate and drying stages, there was no significant impact of the solution type on the total process efficiency expressed as the ratio of dried mass to raw material mass. In spite of the same variants of osmotic dehydration of cherries in both production scales, the dehydration time under industrial conditions was even 11times longer. The technical condition of the tested line was determined as operable. The osmotic dehydration and drying equipment was working correctly. The complexity of repair processes and time-consuming equipment cleaning were demonstrated.

Banana pell pellets for animal feed

The objective was to determine the exact moisture percentage for the formation of pellets from the banana peel, residues of banana candies, and the bromatological analysis of the final product. For the of the peel of banana, 10 different dehydration times were performed: zero; two; four; six; eight; ten; twelve; fourteen; sixteen and eighteen hours of dehydration, with four replicates each treatment. The exact moisture percentage for pellet formation was 18.84% moisture. The final product presented in its bromatological composition 81,16% of DM, 8,59% of CP, 26,8% of TND , 71,48% of NDF, 54,64% ADF, 0,8% of EE, 13,43% MM, 86,54% of OM, 0,22% of P e 0,068% of K. Evaluations in animal models should be performed in place of corn to determine the replacement levels in the diets and the performance of the animals.

Otimização do processamento da farinha e da extração de antocianinas do mirtilo

Abstract The objective of this work was to determine the ideal conditions for the processing of flour and extraction of anthocyanins from blueberries (Vaccinium corymbosum). A central composite design (CCD) with response surfaces was used. For the processing of blueberry flour, different dehydration temperatures (53ºC-67ºC) and times (43.18-48.82 hours) were used. The extraction of anthocyanins was performed with ethanol solutions (15-85% v/v) at different pH values (1.0-4.0). ). The total monomeric anthocyanin content was 1,538.39±25.63 mg 100 g-1 (0.89 desirability value) for fresh blueberries in the optimal extraction condition (53.5% ethanol, 2.5 pH) and 3,101.04±11.57 mg 100 g-1 (0.96 desirability value) for blueberry flour in the optimum processing condition (53ºC, 46 hours). The optimized extraction and dehydration of blueberries provide high levels of anthocyanins in the samples.

Energy consumption and dehydration parameters of microwave drying of carrot

The parameters of microwave dehydration (thickness, mass load, and microwave power level) of carrot slices had a statistically significant (P &lt; 0.05) effect on the drying process. Carrot slices (thicknesses of 3, 6, and 9 mm) were dehydrated as monolayers at microwave power levels (80, 240 W) at different mass loads (1.00, 0.63, and 0.38 kg m-2). The optimal microwave model for the carrot slice microwave dehydration was the model with the microwave power level of 240 W, mass load of 0.38 kg m-2 , and 3 mm thickness, with the shortest dehydration time (15 ± 1 minute) and the lowest energy consumption (0.099 ± 0.002 kWh). The minimum resistance to mass transfer (effective moisture diffusivity) was observed in the models with the thickness of 3 mm, a 1.00 kg m-2 mass load, dehydrated at 80 W (8.2519 × 10-8 ± 8.8815 × 10-10 m 2 s-1). The average activation energy for the analyzed models was 8.972 ± 0.009 W g-1. Therefore, the application of the microwave dehydration method can be considered a proper alternative for the dehydration of carrot slices.

Production aspects of hay of tropical pasture of

Context Tropical pasture have been little explored for haymaking, due to lack of information regarding loss of nutrients and of forage dehydration. Aims This study aimed to evaluate the production aspects of tropical pasture hays. Methods To characterise forage dry mass yield and dehydration rate, we studied the grasses Marandú, Xaraés, Massai, Paredão, Planaltina and Tupã. The water soluble carbohydrates concentration curve, chemical composition and in situ rumen degradability of dry mass, crude protein and neutral detergent fibre were also determined. Key results The highest forage dry mass yield was observed in 2018, when Planaltina and Paredão performed best (6.28 and 5.26 ± 0.41 t of dry matter ha−1, respectively). There was no genotype × dehydration time interaction (P = 0.81) on water soluble carbohydrates. Exposure to sun resulted in a linear decreasing effect (P &lt; 0.01) on water soluble carbohydrates content, with loss of 5.03 g kg−1 for each hour of exposure to the sun during the haymaking process. There was an interaction effect (P &lt; 0.01) between type of material and genotype on the content of dry matter, mineral matter, crude protein and neutral detergent fibre (P &lt; 0.01). In situ degradability of Massai grass dry mass was higher for the hay (758.0 and 253.8 ± 7.9 g kg−1 for hay and in natura material, respectively). Conclusions and implications The greater amount of leaves in relation to stem indicates that Massai grass is more efficient in dehydration during the first hours of exposure to the sun, as well as sustaining lower losses.

Banana pell pellets for animal feed

The objective was to determine the exact moisture percentage for the formation of pellets from the banana peel, residues of banana candies, and the bromatological analysis of the final product. For the of the peel of banana, 10 different dehydration times were performed: zero; two; four; six; eight; ten; twelve; fourteen; sixteen and eighteen hours of dehydration, with four replicates each treatment. The exact moisture percentage for pellet formation was 18.84% moisture. The final product presented in its bromatological composition 81,16% of DM, 8,59% of CP, 26,8% of TND , 71,48% of NDF, 54,64% ADF, 0,8% of EE, 13,43% MM, 86,54% of OM, 0,22% of P e 0,068% of K. Evaluations in animal models should be performed in place of corn to determine the replacement levels in the diets and the performance of the animals.

Identifikasi Tipe Dehidrasi dan Profil Elektrolit Mayor pada Pasien Kucing di Rumah Sakit Hewan Prof. Soeparwi dan Beberapa Klinik Hewan di Wilayah Yogyakarta

Dehydration is defined as a lack of body fluids followed by loss of electrolytes, and changes in acid-base balance. The type of dehydration is limited based on the concentration of sodium in serum at the time of dehydration. Maintenance of osmotic pressure and distribution of several compartments of body fluids are the main functions of the four major electrolytes, namely sodium (Na +), potassium (K +), chloride (Cl‾), and bicarbonate (HCO3‾). Sodium is the most cation in extracellular fluid, most potassium cation in intracellular fluid and chloride is the most anion in extracellular fluid. The purpose of this study was to identify the type of dehydration and to determine the major electrolyte profile in cats in Yogyakarta and its surroundings. This study used 18 sick cats that were thought to be dehydrated, marked by decreased skin turgor, CRT&gt; 2 seconds, and 12 cats that were suspected of having electrolyte balance disorders with symptoms of ascites, uropoetic disorders. Blood was drawn for all cats to measure Pack Cells Volume (PCV) levels. Patient clinical data and patient diagnosis were recorded, cats with changes in serum PCV levels were separated for examination of levels of sodium, chloride, potassium using Seamaty SMT-120V. The type of dehydration is identified based on the sodium level in the serum of a dehydrated cat. The results showed that most of the cat patients were dehydrated had low serum sodium levels (hyponatremia). There was 1 cat patient had low chloride levels. Potassium levels in cats with UT obstruction increased, which led to a decrease in the Na: K ratio. Cat bicarbonate levels did not show any change. From the results of the study it was concluded that dehydration in cats at Prof. Soeparwi is hypotonic dehydration (71%). The sodium profile mostly decreased, chloride and bicarbonate levels did not change, while there were changes in potassium levels in patients with UT disorders. The advice given is to check electrolytes before doing fluid therapy. Prior to electrolyte testing, dehydrated cats can be given a sodium solution.

Microwave-assisted preparation of polyphosphoric acid in a continuous-flow reactor

Abstract Polyphosphoric acid (PPA) is widely used in inorganic salt production, petrochemical industry, electronic material preparation and other manufacturing industries. Conventional preparation methods of PPA has disadvantages of pollution, high energy consumption and long production time. To address this problem, microwave continuous-flow preparation may be a desirable way due to its advantages of environmentally-friendly, rapidity and high efficiency. Therefore, to explore the process of preparing PPA by microwave continuous-flow method, a continuous-flow microwave reactor was designed for the dehydration process of orthophosphoric acid to prepare PPA in this paper. The microwave-assisted dehydration process was studied in comparison with the conventional dehydration process and the “closed” microwave-assisted dehydration process in terms of energy efficiency, process times and treatment capacity. The effect of input microwave power, reduced pressure and inlet flow velocity of orthophosphoric acid on the performance of the dehydration process was studied. The results showed that the influence of the microwave power on the temperature rise process during dehydration is greater than that of the reduced pressure. Moreover, the inlet flow rate has a great impact on the treatment capacity and product quality of the dehydration process. Bedsides, the comparison with the other two methods showed that microwave heating can effectively shorten the dehydration time, and the continuous-flow treatment can effectively improve the treatment capacity of microwave heating. The perspectives of the process scale-up by continuous-flow microwave heating method is also discussed.

Possibility of Pulsed Electric Field and Essential Oil Pre-treatment, Microwave-air Dehydration to the Quality of the Dehydrated Sesban (Sesbania sesban) Flower

Non-heat ahead-treatment in advance of the main dehydration is essential to preserve the quality and ensure food safety. Pulsed electric field (PEF) utilizes a high-voltage electric field in a very short duration to inhibit microbes and enzymes while maintaining the most sensory and nutritional characteristics. For thermal sensitive components, the dehydration process should be performed at low temperatures. Freeze dehydration, vacuum dehydration required high cost for equipment, energy consumption, low quantity in long dehydration time. Microwave-air dehydration is considered as a promising alternative technical approach. Sesban (Sesbania sesban) flower contains numerous phytochemical components promoting health-benefit. However, it’s highly perishable after harvesting. Consumers enjoy the dried sesban flower as a healthy drink. This study examined the possibility of PEF ahead-treatment in microbial inhibition and enzymatic inactivation; essential oil and Microwave-air dehydration on retention of total phenolic content (TPC), vitamin C, 2,2 diphenyl-1-picrylhydrazyl of free radical scavenging (DPPH), ferric reducing antioxidant power (FRAP) of the dehydrated sesban flower. Research also monitored the microbial stability of the dehydrated sesban flower during 12 months of preservation. Results showed that PEF at pulse strength 1000 kV/cm, pulse duration 90 µs, pulse number 45 was remarkably inactivated polyphenol oxidase and peroxidase in raw material. Rosemary essential oil soaked for sesban flower before dehydration positively preserved the ascorbic acid, phenolic content and antioxidant capacity. These PEF and essential oil ahead-treatments strongly facilitated for the main Microwave-air dehydration. Among different air temperatures from 20°C to 40°C in microwave-air dehydration, the highest Vitamin C, TPC, DPPH and FRAP of the dried flower were recorded at air temperature from 20°C to 30°C with no significant difference. Meanwhile, airspeed 1.2 m/s showed the highest Vitamin C, TPC, DPPH and FRAP of the dried flower with no significant difference with airspeed 1.4 m/s and 1.6 m/s. There was no significant difference in Vitamin C, TPC, DPPH and FRAP of the dried flower by microwave power from 1.15 to 1.45W/g. Therefore, a combination of microwave and air dehydration at air temperature 25°C, airspeed 1.2 m/s, the microwave energy density of 1.45 W/g was recommended to better preserve vitamin C, TPC, DPPH, FRAP. Microbial stability of the dehydrated flower was also observed during 12 months of storage by 3 month-interval sampling. Coliform, yeast and mold criteria in dried product were stable within acceptable limits.

Closed flow solar dehydration with the use of silver nanoparticles: Application for the production of Pouteria lucuma flour

In this research, a closed-flow solar dehydrator with a refrigeration moisture extraction system was evaluated, likewise, the dehydration temperature time was optimized by evaluating three types of heat transfer fluids. The dehydration equipment included devices to absorb thermal energy from incident sunlight, such as a trombe wall and a parabolic cylindrical collector, and a thermo bank system. In addition, the influence of three types of heat transfer fluids (water, oil and oil nanofluid + silver nanoparticles) was evaluated. This dehydration system was applied to process the Pouteria lucuma fruit. The results indicate the reduction of the dehydration time by 58.19% using nanofluid. This treatment prevents the modification of the physicochemical properties of the product and helps preserving its organoleptic properties.

Dehydration behaviour and impurity change of phosphogypsum during calcination

The preparation of β-hemihydrate gypsum is an important approach for large-scale utilization of phosphogypsum (PG) because of the simple production technology by calcination. However, the dehydration behaviour and impurity change during the transformation of PG to β-hemihydrate gypsum at low temperatures are unclear. In this study, the dehydration of PG at different temperatures was investigated by a calcination test and in-situ X-ray diffraction analysis. The variation in crystal morphology and structure of PG was clarified using scanning electron microscopy and Materials Studio software. Furthermore, the change of impurity was analyzed by energy-dispersive spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy measurements. The results show that the dehydration of PG to β-hemihydrate gypsum depends on calcination temperature and time. Moreover, an increase in the calcination temperature could accelerate the dehydration of PG and shorten the dehydration time; meanwhile increasing the calcination time or calcination temperature could make a part of β-hemihydrate gypsum further dehydrate to anhydrite. The morphology and elemental distribution of PG did not dramatically change during calcination, but the grain size decreased and the elemental distribution density increased. It should be noted that the calcination did not decrease the phosphorus and fluorine contents in PG at 120 °C, whereas the contents increased due to the removal of crystal water. The phosphorus impurity form transformed from CaHPO4·2H2O and Ca(H2PO4)2·H2O to CaHPO4 and Ca(H2PO4)2, respectively. Therefore, the calcination could not remove the phosphorus and fluorine from PG, and pretreatment is required to reduce the adverse effects of impurities in the industrial production of β-hemihydrate gypsum.