Optimum Drying Conditions Research Articles

Microwave drying of germinated corn and its effect on phytochemical properties.

Drying is a preservation method that removes or reduces the moisture content of a product. This process can affect the nutritional properties of agricultural crops. Therefore this research sought to investigate the effect of microwave drying power (100-700 W) on the drying rate, effective diffusivity, β-carotene content (BCC), total flavonoid content (TFC), total phenolic content (TPC) and antioxidant capacity of sprouted corn, which can be applied as a rich antioxidant source. With increasing microwave drying power from 100 to 700 W, the effective diffusivity was in the range from 1.50 × 10-6 to 1.81 × 10-5 m2 s-1 , while BCC ranged from 614.20 ± 3.10 to 229.90 ± 1.00 µg β-carotene equivalent g-1 dry weight (DW), decreasing gradually by 62.57%. Meanwhile, TPC and TFC of samples dried at 300 W were the highest, with levels of 315.94 ± 0.69 mg gallic acid equivalent g-1 DW and 190.16 ± 1.33 mg catechin equivalent g-1 DW respectively, which were higher by 8.66 and 98.97% as compared with samples dried at 100 W. Similar development was found in the antioxidant ability of germinated corn. Drying at a microwave power of 300 W provided the highest nutritive and antioxidant values. The results of this study are useful in the selection of optimal drying conditions during microwave drying of germinated corn, as a baseline for other agricultural crops. © 2016 Society of Chemical Industry.

Experimental optimization of microwave drying zinc oxide leach residues by response surface methodology

Abstract Response surface methodology (RSM) and Box-Behnken design (BBD) were applied to experiment optimization of microwave drying zinc oxide leach residues (ZOLR). The effects of different factors involving temperature, drying time, material mass, material thickness and their interaction on moisture content and dehydration rate of ZOLR were investigated. Two second-order polynomial models for moisture content and dehydration rate of ZOLR were established by multivariate regression analysis. Analysis of variance shows that all independent variable and quadratic terms of the four factors have significant influence on moisture content and dehydration rate of ZOLR. The optimum drying conditions are as follows: temperature is 93.41°C, drying time is 15.9 min, sample mass is 77.91 g and material thickness is 17 mm. The predicted values of moisture content and dehydration rate were 10.98% and 1 g/min, which were close to experimental values 11±0.03% and 1±0.01 g/min under the optimal conditions. Infrared spectra analysis show that no chemical reactions took place in the process of microwave dying ZOLR and only a part of the absorbed water was removed in the sample.

The Effect of Drying Parameters on the Quality of Pork and Poultry-Pork Kabanosy Produced according to the Traditional Specialties Guaranteed Recipe

The aim of this study was to determine the effect of differentiated air relative humidity during the drying process on selected quality features of TSG (traditional specialties guaranteed) pork and poultry-pork kabanosy. After heat treatment and 24-hour cooling at 4–6°C, the products were placed in three chambers at 15°C with differentiated air relative humidity: 60, 70, and 80%, respectively. The drying process was carried out until all variants of kabanosy achieved the required final yield of the product (<68%). Color components, water activity and shear force, water, protein, fat, and salt content, and the TBARS indicator values were determined. The drying process might be shortened (~50%) by a reduction of humidity in the drying chamber from 80 to 60%. The changes in the content of chemical components in pork kabanosy compared to poultry-pork ones demonstrated the different dynamics of the drying of the two types of kabanosy and the need for the selection of optimum drying conditions relative to raw material composition.

Rehydration and Textural Properties of Dried Konjac Noodles: Effect of Alkaline and Some Gelling Agents

Konjac glucomannan flour, which mainly consists of glucomannan, is an indigestible dietary fiber. Therefore, it has been broadly used as low-calorie food ingredient in various kinds of foods, beverages, and pharmaceutical products. In this study, the production of dried konjac noodles was evaluated by studying the effects of alkalinity using limewater versus calcium hydroxide and the gelling agent sodium alginate on textural properties of konjac noodles. Drying and rehydration conditions were studied to evaluate the optimum conditions for producing dried konjac noodles. By considering the springiness and cohesiveness of the konjac noodles, the results indicated that using 3% konjac glucomannan flour with limewater and an incubation time of 30 min were the most suitable conditions. In addition, hot air drying at 80 °C for 55 min and soaking in hot water for 9 min were the optimum drying and rehydration conditions.

Microencapsulation of walnut oil by spray drying: Effects of wall material and drying conditions on physicochemical properties of microcapsules

Abstract In this study, the effects of wall material formula and spray drying conditions on physicochemical properties of walnut oil microcapsules were investigated. Three different wall materials including skim milk powder (SMP), SMP + Tween 80, and SMP + maltodextrin were used for emulsion preparation. The prepared emulsions were analyzed for droplet size and stability. The emulsions were then dried in a pilot-scale spray dryer equipped with a two-fluid nozzle at different inlet drying air temperatures and feed atomization pressures in order to determine the optimal drying conditions for maximizing the microencapsulation efficiency. The microencapsulation efficiency, particle size distribution, sphericity, moisture content, bulk density, and morphology of produced microcapsules were also measured experimentally. In addition, the microcapsules with the highest microencapsulation efficiency obtained from each wall material were subjected to surface coverage of oil test using electron spectroscopy for chemical analysis (ESCA) after 60 days of storage at room temperature. The emulsion prepared using SMP and Tween 80 combination as wall material resulted in the highest microencapsulation efficiency (91.01%) at drying air temperature of 180 °C and feed atomization pressure of 3 bar. The lowest surface coverage of oil was also observed for microcapsules covered by SMP and Tween 80 combination. Scanning electron microscopy (SEM) observations showed almost no cracks or fissures on the surface of microcapsules produced using SMP and Tween 80 combination at the optimal drying condition. Industrial relevance Walnut oil contains highly valuable constituents such as essential fatty acids, tocopherols, and phytosterols. However, a direct application of this functional oil in processed foods is problematic due to its low solubility and susceptibility to oxidation. These issues could be greatly overcome by using microencapsulation technology. Nowadays, this technology has received an increasing attention in food and pharmaceutical industries due to its unique features in protecting the functionality of ingredients. Spray drying technology is one of the most frequently used techniques for this aim. However, comprehensive studies need to be carried out in order to determine suitable operational conditions of spray drying system for improving physicochemical properties of finished powder.

Optimization of microwave-assisted fluidized-bed drying of carrot slices

ABSTRACTThe drying of carrot slices in a microwave-assisted fluidized-bed drying (MWFBD) system was investigated. The drying conditions such as the initial microwave power density and the inlet air temperature were optimized. The effects of different pretreatment processes such as water blanching, osmotic drying with 20% sugar solution, and 1% citric acid solution on the drying of carrot slices were investigated under the optimized drying conditions. The drying kinetics and the physical properties of the dried carrot slices were analyzed. Different mathematical models of the drying process were explored and fitted to the drying of carrot slices in MWFBD. The pretreatment of the carrot slices reduced the drying time required and improved the qualities such as color and textural strength of the dried carrot slices.

1차 열풍건조 한 고추 다진 양념의 원적외선 건조특성

The purpose of this study was to verify the drying characteristics of seasoned red pepper sauce and establish optimal drying conditions for far infrared drying of seasoned red pepper sauce. Seasoned red pepper sauce, which was dried by heated air, was used. One kg of seasoned red pepper was spread at thicknesses of 10 and 20 mm and dried by a far infrared dryer until a final moisture content of 15±0.5%. The far infrared dryer conditions were air velocity of 0.6, 0.8 m/s and drying temperatures of 60, 70, and 80°C. The drying models were estimated using a determination coefficient and root mean square error. Drying characteristics were analyzed based on factors such as drying rate, color changes, content of capsaicinoids, and energy consumption. The results can be summarized as follows. The drying rate (that is, drying time) tended to be reduced as temperature and air velocity for drying increased. The Page and Henderson models were suitable for drying of seasoned red pepper sauce by a far infrared dryer. Redness decreased after far infrared drying under all experimental conditions. The color difference was 18.18 under the following conditions: thickness 20 mm, temperature 70°C, and air velocity 0.8 m/s. This value was slightly higher than those under other far infrared drying conditions. The capsaicinoid properties of seasoned red pepper sauce decreased under all far infrared drying conditions. The highest capsaicin (19.91 mg/100 g) and dihydrocapsaicin (12.87 mg/100 g) contents were observed at a thickness of 10 mm, temperature of 80°C, and air velocity of 0.8 m/s. Energy consumption decreased with higher temperature, slower air velocity, and thinner seasoned red pepper sauce.

Drying kinetics of cotton based yarn bobbins in a pressurized hot-air convective dryer

In this study, the drying kinetics of cotton bobbin drying process in a pressurized hot-air convective bobbin dryer was investigated, and a drying model was introduced for the simulation of drying. Tests were conducted for drying temperatures of 70℃, 80℃, and 90℃; effective drying air pressures of 1, 2, and 3 bars; three volumetric flow rates of 42.5, 55, and 67.5 m3/h; and for three different bobbin diameters of 10, 14, and 18 cm. Optimum drying conditions were specified in terms of drying time and energy consumption. Results indicate that the total drying time depends significantly on the drying temperature, pressure, and volumetric flow rate. Results show that the minimum energy consumption is obtained for low values of drying air temperatures and pressures, and for moderate and high values of drying air volumetric flow rates. It was also found that the Page model is suitable for simulating the drying behavior of cotton yarn bobbins. Finally, results show that effective diffusion coefficient values are between 1.132 × 10−7 m2/s and 3.453×10−7 m2/s depending on the values of drying parameters.

The Effects of Drying on Physico-Chemical Properties and Antioxidant Capacity of the Brown Alga (Hormosira banksii (Turner) Decaisne)

Hormosira banksii is a rich source of polyphenols, which can be utilized in the food or pharmaceutical industries. This study aimed to determine the impact of six drying methods on properties of the alga H. banksii. Our data revealed that drying conditions significantly affected recovery yield, residual moisture, extraction yield, total phenolic content (TPC) as well as antioxidant capacity of H. banksii (P < 0.05). Optimal conditions for oven, vacuum and de-humidification were 40, 50 and 50C, respectively, and microwave power is 840 W. Under optimal conditions, H. banksii prepared by freeze, de-humidification and vacuum had significantly higher levels of TPC, total flavonoid content (TFC) and proanthocyanidins as well as possessing stronger antioxidant capacity in comparison with those prepared by sun, microwave and oven drying methods. As freeze drying is costly and time-consuming, de-humidification (50C, air in and out of 11.1 and 15.4%) and vacuum (50C, 10 psi) were recommended for drying H. banksii Practical Applications Algae possess various antioxidants with potential benefits for health. Drying is considered as a method for preserving materials, transport with low costs and especially first step for extraction, isolation and purification of active compounds. Thus, it is important to investigate the effects of drying conditions on the properties of the dried alga H. banksii. From the findings, the different drying conditions significantly affected the phytochemical profile and antioxidant activity of the dried alga and the optimal drying conditions could be applied for preparation of dried H. banksii for further processing (extraction, fractionation and isolation of bioactive compounds) as well as potential industrial applications (as a reference for drying H. banksii and other algae).

Influence of Air-Drying on the Quality Characteristics of Spearmint: Effects of Air Temperature and Velocity

Dry spearmint is a commodity widely used in food manufacturing both as an ingredient and a product itself. The objective of this study was to determine the effect of different drying temperatures and air velocities on the quality of dried product in an attempt to recommend the optimum drying conditions. Physicochemical and microbiological properties were evaluated as quality indexes. Results revealed that temperature and air velocity were statistically significant for most of the parameters investigated. Taking into consideration that consumers have a preference towards dried herbs that retain the characteristics of the fresh material, the suggested combination for drying spearmint is at 40C with an air velocity of 3 m/s. This combination has been experimentally demonstrated that can also significantly improve the microbiological quality of the product. Practical Applications Drying process is often applied to preserve and increase self-life of leafy aromatic plants through decreasing moisture content and water activity. Through the present work the effect of air-drying on the quality attributes of dried spearmint was investigated. Different combinations of temperature and air velocities were tested in an attempt to determine the most suitable drying parameters that will lead to a high quality product. The application proposed at 40C with an air velocity of 3 m/s can be adopted by manufactures in industrial scale. The aforementioned combination produced dried spearmint with the best physicochemical and microbiological characteristics.

Processing optimization of restructured jerky from sea rainbow trout frame muscle.

This study determined optimal drying temperature and time on the moisture content, hardness, and overall sensory acceptance of restructured jerky from sea rainbow trout frame muscle (RJ-SRTF) using response surface methodology. The optimal drying conditions with respect to the above variables were 67.2°C for drying temperature and 8.6 h for drying time. The predicted values of response optimal conditions were 18.8 g/100 g for moisture content, 495.8 g/cm2 for hardness, and a score of 7.2 for overall sensory acceptance. The actual values obtained in this experiment were 19.1±0.6 g/100 g for moisture content, 453.9±91.0 g/cm2 for hardness, and a score of 7.4±0.5 for overall sensory acceptance. Both actual and predicted values were nearly identical. In conclusion, the models are adequately fitted to experimental data and suitable for optimization.

Convective drying of papaya seeds (Carica papaya L.) and optimization of oil extraction

The convective air drying of papaya seeds was studied in order to optimize the seed oil yield. Papaya seeds were dried under different conditions of air temperature and air velocity. The operation was characterized by drying rate and drying kinetic curves. Oil was extracted from the seeds, obtained in all drying conditions and, the yield was optimized. The results revealed that the constant rate and falling rate periods occurred during the convective air drying of papaya seeds. The Overhults kinetic model was suitable to represent the experimental drying curves. The optimal drying conditions, which provided the maximum seed oil yield, were: air temperature of 70°C and air velocity of 2.0ms−1. In these conditions, the seed oil yield was 19.23% and the final moisture content was 7.40% (w.b.). High quality oil, with about 90% of oleic acid, was obtained from papaya seeds.

Drying Characteristics of Sea Tangle Using Combination of Microwave and Far-Infrared Dryer

Purpose: The present study is aimed at examining the drying characteristics of sea tangle through a combination of microwave and far-infrared drying experiment and finding the optimal drying conditions. Methods: Sea tangle was cleaned and cut into fine pieces (5mm) before they were subjected to combinational drying by microwave and far-infrared ray. The amount of specimen per drying is 2 kg. The finely cut pieces of sea tangle were preheated in a microwave dryer for three different lengths of time (10, 15, and 20 min). Subsequently, they were dried using a far-infrared dryer at tow temperatures (90°C and 100°C) at an air velocity of 0.8 m/s until the final moisture content reduced to 10%. Results: Sea tangle dried under the condition of 20 min of preheating in the microwave dryer and drying at 100°C by the far-infrared dryer. Of the drying models verified in this study, the logarithmic model showed high accuracy with the coefficient of determination R 2 >0.7825 and RMSE <0.1095. The rehydration ratio of sea tangle was the highest (12.87 g water/g dry matter) under the condition of 15 min of preheating in the microwave dryer and drying at 100°C by the far-infrared dryer. The energy consumption for the combination of microwave and far-infrared drying was the lowest (4.78 kJ/kg water) under the condition of 20 min of preheating in the microwave dryer and drying at 100°C by the far-infrared dryer. Conclusions: Considering the drying time, discoloration during drying, rehydration ratio, and energy consumption for the drying of sea tangle, the optimal drying conditions for high-quality sea tangle are 15 min of preheating in a microwave dryer and drying at 100°C by a far-infrared dryer.

Modeling and optimization of red currants vacuum drying process by response surface methodology (RSM)

Fresh red currants were dried by vacuum drying process under different drying conditions. Box–Behnken experimental design with response surface methodology was used for optimization of drying process in terms of physical (moisture content, water activity, total color change, firmness and rehydratation power) and chemical (total phenols, total flavonoids, monomeric anthocyanins and ascorbic acid content and antioxidant activity) properties of dried samples. Temperature (48–78°C), pressure (30–330mbar) and drying time (8–16h) were investigated as independent variables. Experimental results were fitted to a second-order polynomial model where regression analysis and analysis of variance were used to determine model fitness and optimal drying conditions. The optimal conditions of simultaneously optimized responses were temperature of 70.2°C, pressure of 39mbar and drying time of 8h. It could be concluded that vacuum drying provides samples with good physico-chemical properties, similar to lyophilized sample and better than conventionally dried sample.

Forced Convective Drying of Wastewater Sludge with the Presentation of Exergy Analysis of the Dryer

The main objective is studying the fundamental aspect, by means of drying kinetics and the application of forced convective drying of wastewater sludge with the determination of the optimum drying conditions. The drying system is composed of two units; small samples of 2.5 g are dried in the first unit and a bed of sludge weighing 250 g is dried in the second unit. The experiments are performed under air temperatures varying between 80°C and 200°C. The range of the air velocity and its humidity is 1–2 m/s and 0.005–0.05 kgwater/kgdry air, respectively. The experiments are performed for two different sludges: activated sludge (AS) and thermalized and digested sludge (TDS). Usually, three main drying phases are observed during drying of bed of sludge. These phases are reduced to only two for small samples. Determination of the influent parameters shows that the temperature of the drying air and sludge origin can profoundly influence the drying kinetic of the sludge. The exergy analysis of the two units of the drying system allows selecting 140°C, 2 m/s, and 0.05 kgwater/kgdry air as optimum drying conditions with an exergy efficiency reaching 90%.

Optimization for vacuum belt drying process of Qibai Pingfei granule through response surface methodology

Based on single factor tests,the optimum vacuum belt drying conditions of Qibai Pingfei granule were obtained through Box-Benhnken central combination design and RSM. In this study, drying time, drying temperature and extract density were chosen as independent variables, while transferring rate ginsenoside Rg₁, Re, Rb₁and astragaloside IV were taken as dependent variables. The optimum parameters are as follows: drying time of 112 min, drying temperature of 87 °C and extract density of 1.30 g · mL⁻¹. At the optimum condition, transferring rate ginsenoside Rg₁+ Re, Rb₁and astragaloside IV were 88.01%, 87.31%, 84. 34%. Above all, the optimum processing parameters of vacuum belt drying of Qibai Pingfei granule is reasonable and feasible, which can provide reliable basis for production.

Microwave and blanch-assisted drying of white yam (Dioscorea rotundata).

The effect of microwave and blanch pretreatments on the drying kinetics and quality of white yam (Dioscorea rotundata) was investigated. Yam cubes destined for hot air drying at temperatures 70-90°C were predried in a domestic microwave or blanched in hot water for 1-5min. Microwave pretreatment time had a positive significant effect on drying rate but both pretreatments had a negative influence on the ascorbic acid content and the nonenzymatic browning. The optimum drying conditions were a microwave pretreatment time of 5min and a temperature of 70°C and a blanching time of 1min at a temperature of 80°C. Among the models fitted, the Midilli etal. and the Page models gave the best fits for yam cubes predried with microwave and blanch, respectively. The effective moisture diffusivity for microwave-assisted drying increased from 1.05×10(-8)m(2)s(-1) to 2.00×10(-8)m(2)s(-1) while the hot water blanched samples decreased from 1.53×10(-8) to 8.81×10(-9)m(2)s(-1) with time. The study demonstrates that microwave-assisted drying could be used to enhance heat and mass transfer processes to produce better quality dried yam products.

Optimization of Hemicellulose Coating as Applied to Apricot Drying and Comparison with Chitosan Coating and Sulfite Treatment

AbstractDrying of hemicellulose‐coated apricots was compared to sulfuring and chitosan coating. Air velocity, temperature and hemicellulose concentration were optimized using the Box–Behnken response surface methodology against total color change (ΔE*), yellowness (Δb*) and final moisture content. Drying kinetics were evaluated by Newton, Page and Logarithmic models. Diffusion coefficient, activation energy and rehydration rate were calculated. The optimal drying conditions were found as 1 m/s of air velocity, 80C of air temperature and 3% (w/v) hemicellulose coating, which gave values of 15.2, −8.3 and 26% for ΔE*, Δb* and final moisture, respectively. The hemicellulose‐coated apricots indicated better color values than the uncoated and chitosan‐coated samples, while sulfuring still attained the best color values. Drying kinetics were best described by the Logarithmic model at 60 and 70C and Page model at 80C for 2% hemicellulose coating. Effective diffusion coefficients ranged from 2.499 to 5.742 × 10−9 and the activation energy was calculated as 33.78 kJ/mol. The hemicellulose‐coated apricots had slightly higher rehydration rate than the uncoated and sulfured samples. In conclusion, hemicellulose coating showed a promise for use in fruit drying.Practical ApplicationsTreatment of fruits with sulfur compounds (sulfur dioxide gas, sulfite solutions, etc.) prior to drying is a common practice to minimize loss in the quality of the dried fruit. In fact, use of these chemicals in foods is limited and the allowed concentration varies with countries worldwide in the range of 300–2,000 mg/kg. Because sulfur compounds can cause health problems, use of natural, renewable and abundant preservatives will be a viable alternative. In this respect, hemicellulose extracted from agricultural and food wastes can provide a low‐cost preservative and can be utilized to preserve fruits during drying. The results of this study will also provide a basis to utilize hemicellulose in various fruits other than apricots during drying and meanwhile will help reduce the concentration of sulfur compounds in foods.

MODELING AND OPTIMIZATION OF MICROWAVE DRYING OF TURMERIC SLICES

This study was conducted to evaluate the effects of microwave power at 164, 465 and 752 W on the quality of turmeric slices and determine the suitable drying model that can predict the product’s moisture ratio at any time of the drying process. Dried product quality was measured based on color changes using L*, a and b*. Color quality changes of dried turmeric slices were highest at 752 W quantified by L* and b* values; in contrast, a* value and total color difference (TCD) did not significantly differ with microwave power. Results were successfully determined by the Box-Behnken’s response surface methodology. The experimental data were fitted to three thin layer drying models (Newton, Page and Logarithmic). The Page and Modified Page model were found as good models to predict the drying behavior of turmeric slices. The Page model was however the most satisfactory giving the highest coefficient of determination (0.9987-0.9993) and lowest chi-square (0.7A—10(-4)-2.61A—10(-4)) and root mean square error (0.0079-0.0142). Using the model, the optimum drying conditions that gave the lowest total color difference of 3.44 were 443.93 W microwave power with 5.1% ascorbic acid and 55.6 s drying time.

The effect of drying on timber frame connections post flooding

Timber structures face a unique risk from flooding. Elevations in moisture content due to prolonged wetting will lead to a reduction in the mechanical properties of the building. Despite recent growth of timber construction in the UK and a known increased risk from flooding, little research has been conducted into its effects on light frame timber construction and the most efficacious drying method. This paper presents the results of experiments to determine the optimum drying conditions for light timber frame construction with oriented strand board sheathing after simulated flooding. A series of specimens were wetted for 5 d to simulate flooding before exposure to different environments. The specimens were load tested and values of ultimate strength, yield strength and stiffness were compared to those of un-wetted control specimens. It was found that the optimum drying condition for recovery of the maximum pre-wetting mechanical properties was an environment of 38°C and 40% relative humidity. Although this is an optimal setting there is still a permanent reduction in the mechanical properties of approximately 40% for strengths and 20% for stiffness. Stiffness is dependent on grain orientation; however, strength was found to be independent of grain orientation, as it is governed by the oriented strand board failure.