Drying Air Temperature Research Articles

Numerical analysis of the energy efficiency of drying a flooded masonry wall by applying a variable drying air temperature profile

The masonry wall initially saturated with moisture and without internal or external water sources was considered to simulate the drying of a wall after a flood. Numerical calculations using the in-house non-equilibrium heat and moisture model were performed to investigate the impact of variable drying air temperature profiles on the drying efficiency of the thermo-injection method. A drying process lasting twelve days was simulated. Based on previous studies, four drying air temperature variation strategies, i.e., jump, stepwise, periodic, and constant temperature (reference), were computed and compared. The drying air temperature profile was changed from 20°C to 60°C with heating intervals of 24 h and different characterization strategies. The jump strategy changed rapidly in a single step. Stepwise one changed by 10°C after each heating interval, and the period strategy changed from 20°C to 60°C or from 60°C to 20°C after each heating interval. Furthermore, the relative humidity of the drying air corresponded to the three seasons in Poland (i.e., winter, summer, and spring) and ranged between 70% and 90% at ambient conditions. It was found that the proposed drying strategies with variable temperature profiles can reduce energy consumption compared to the reference strategy with a constant temperature.

Foam mat drying of coffee aqueous extract: Foam process optimization, drying kinetics, energy consumption, and energy efficiency analysis

The instant coffee consumption has been growing mainly due to consumer's search for quick-prep foods. Foam mat drying (FMD) is an innovative technique that promises energy savings for industries. The instant coffee production by FMD was evaluated by identifying the best foaming conditions and analyzing the kinetics and energy aspects of drying. The effect of albumin concentration (3.5–6.5 % w/V), whipping time (2.5–12.5 min) and stand mixer rotation speed (975.67–1066.67 rpm) on properties of foamed coffee extract (FCE) was investigated using a desirability function. FCE at optimal condition (5.05% w/V, 6.5 min and 1066.67 rpm) was dried in oven (50–90 °C). Increasing the drying air temperature reduced the process time due to the increase in the drying rate and resulted in reductions in specific energy consumption and CO2 emissions. Energy efficiency was reduced over time. These results show that FMD is a promising technique to produce instant coffee.

The modeling and simulation of a smoke-free firewood furnace designed for indirect heating adapted to mixing heating configuration

The use of wood furnaces for thermal energy applications in drying is common among coffee growers in Brazil. However, incomplete combustion of firewood and excessive use of damaged furnaces can lead to product contamination and negative environmental effects. To address this issue, a smoke-free wood furnace was designed, to heat the drying air utilizing a heat exchanger, and using a removable smoke-free combustion cell. The new furnace design was based on thermal energy ranging from 15 to 30 kW, drying airflow rates from 35 to 45 m³ min-1, and drying air temperatures from 50 to 80 °C. The design process considered the thermal energy required for heating air, furnace fuel consumption, combustion chamber volume, grate area, and heat exchanger dimensions. The performance of the adapted furnace data was monitored over time using a graphics statistical control (x-bar chart). Regression analysis of temperature and mass flow rate for the mixed heating configurations was carried out to develop quadratic models for the modified operation. The models were used to create a simulation model using ExtendTM simulation language to predict the performance of the furnace, in mixed heating at the desired drying air temperature. The simulation was carried out under two different conditions, normal and controlled operation of the furnace. Five scenarios of working hours without refueling (119 min) drying temperature were carried out. The simulation result indicates that the furnace operates at a maximum efficiency of approximately 40% irrespective of the desired drying temperature during normal operation. However, controlled operation with increased opening time of the mixing air inlet for admitting ambient air into the mixing chamber significantly improved the furnace's efficiency, with an optimum efficiency of 55% achieved at 90°C drying temperature. The simulation reflects that the furnace operates at a maximum efficiency of 68% at a temperature of 90°C, which can be attained at 66.31 minutes of operation in mixed heating of 30 minutes and indirect heating configuration of 89 min during working hours without refueling of 119 min.

Computer-Aided Neuro-fuzzy Algorithm for Prediction of Ginger(Zingiber officinale) Rhizome Drying

Neuro-fuzzy modeling technique has been used for the development of computer-based adaptive process control systems for most postharvest operations instead of convectional mechanistic modeling technique owing to its good prediction without prior knowledge of process operation. Therefore, adaptive neuro-fuzzy inference system (ANFIS) modeling and prediction of ginger (Zingiber officinale) rhizome moisture content in a forced convective tray dryer was investigated in this study. Computer codes for an exhaustive search and grid partitioning were written in the Matlab software environment and used for the analysis of experimental data obtained from the ginger rhizome drying experiment. The data were trained and checked using the grid-partitioning ANFIS method for the development of neuro-fuzzy network for ginger drying prediction. The prediction accuracy of the network was evaluated by varying input and output Membership Function (MF) types. The exhaustive search analysis shows that drying time (DT) has the highest effect on the moisture content, followed by air drying temperature (ADT), air relative humidity (ARH), and air flow velocity (AFV). Moreover, combination of DT and ADT as two interactive variables; and combination DT, ADT and ARH as three interactive variables show highest effect on ginger moisture content removal during the process. Generalized bell (gbell) MF with two MF for each input variable and constant output MF 2 type were obtained as the best ginger drying ANFIS network with corresponding R and MSE of 0.9667 and 0.0971, respectively. Therefore, this study shows the reliability of the ANFIS model for the prediction of ginger rhizome drying in a tray dryer.

Computer-Aided Neuro-fuzzy Algorithm for Prediction of Ginger(Zingiber officinale) Rhizome Drying

Neuro-fuzzy modeling technique has been used for the development of computer-based adaptive process control systems for most postharvest operations instead of convectional mechanistic modeling technique owing to its good prediction without prior knowledge of process operation. Therefore, adaptive neuro-fuzzy inference system (ANFIS) modeling and prediction of ginger (Zingiber officinale) rhizome moisture content in a forced convective tray dryer was investigated in this study. Computer codes for an exhaustive search and grid partitioning were written in the Matlab software environment and used for the analysis of experimental data obtained from the ginger rhizome drying experiment. The data were trained and checked using the grid-partitioning ANFIS method for the development of neuro-fuzzy network for ginger drying prediction. The prediction accuracy of the network was evaluated by varying input and output Membership Function (MF) types. The exhaustive search analysis shows that drying time (DT) has the highest effect on the moisture content, followed by air drying temperature (ADT), air relative humidity (ARH), and air flow velocity (AFV). Moreover, combination of DT and ADT as two interactive variables; and combination DT, ADT and ARH as three interactive variables show highest effect on ginger moisture content removal during the process. Generalized bell (gbell) MF with two MF for each input variable and constant output MF 2 type were obtained as the best ginger drying ANFIS network with corresponding R and MSE of 0.9667 and 0.0971, respectively. Therefore, this study shows the reliability of the ANFIS model for the prediction of ginger rhizome drying in a tray dryer.

Impact of Air-Drying Temperatures on Drying Kinetics, Physicochemical Properties, and Bioactive Profile of Ginger.

Ginger (Zingiber officinale Roscoe) is a perishable commodity that requires proper processing to maintain its bioactivity. This study evaluated the effect of different air-drying temperatures (50 °C, 60 °C, and 70 °C) on ginger's drying kinetics and quality attributes. For an enhanced understanding of the drying kinetics, we employed a detailed approach by combining an existing drying model (namely, Midilli) with the Arrhenius model. This combined model facilitates a thorough analysis of how temperature and time concurrently affect the moisture ratio, offering more profound insights into the drying mechanism. A higher drying rate was achieved at 70 °C, yet elevated drying temperatures could compromise the quality attributes of ginger slices. Ginger slices dried at 50 °C displayed improved physicochemical properties and less color browning. The evaluation of the bioactivity profile of resultant ginger extracts also revealed higher total phenolic contents (1875.87 ± 31.40 mg GAE/100 g) and DPPH radical scavenging activity (18.2 ± 0.9 mg TE/kg) in 50 °C treated ginger samples. Meanwhile, the hydroethanolic mixture (70% ethanol) was also reorganized with better extraction efficiency than water and MWF (a ternary blend of methanol, water, and formic acid) solution. The promising outcomes of this study endorse the influence of drying temperature on the quality characteristics and bioactive profile of ginger and the selection of suitable extraction solvents to acquire phenolic-rich extract.

Performance comparison of a fixed-bed solar grain dryer with and without latent heat storage

Latent heat storage has gained attention as an energy storage method for solar drying due to its high storage density. However, its overall impact in drying performance has not been sufficiently investigated. This study presents detailed, validated mathematical models necessary for the transient simulation of a solar dryer with latent heat storage with the aim of assessing the effect that such storage has on the deep bed drying of wheat. Computer simulations were run with weather data from Germany. A fixed bed dryer with a capacity of one ton was assumed and the size of the solar air heater and latent heat storage unit was varied, as well as the type of phase change material. In drying wheat without storage from 22% to 13% w.b. (0.28 to 0.15 kg kg−1 d.b.), increasing solar collecting area from 6 to 15 m2 reduced drying time by around 50% but resulted in excessive temperatures. At equal collecting area, the use of latent heat storage changed drying time by −5% to +13.9% depending on component sizes, but the drying air temperature was limited effectively if solar collection and storage units are properly sized in relation to each other. Failure to do so can result in higher drying temperatures than recommended or bring little additional benefit. Moisture uniformity at the end of drying was slightly improved by up to 10% in the presence of the storage unit due to a reduction in the average drying temperature. The presented models and corresponding simulation programs are a useful tool to size the components of a solar dryer with and without latent heat storage.

Artificial neural network for drying behavior prediction of paddy in developed chamber fluidized–bed dryer

After rice is harvested, it must be dried before its products can be stored. Therefore, this paper presented a novel and simple method for improving paddy drying process in a column fluidized bed dryer. Additionally, artificial neural network methods were applied to predict the drying behavior. The experiments were conducted under two different drying chamber characteristics (a conventional chamber and a chamber fitted with nozzle) and four different air flow velocities (3.03, 3.52, 4.12 and 4.85 m/s) at a drying air temperature of 60 °C. The results showed that the chamber fitted with the nozzle reduced the drying time by approximately 67, 52 and 38 % at the air velocity of 3.52, 4.12 and 4.85 m/s, respectively. The specified experimental conditions and the calculated moisture content of the paddy in this work were used as input and output data for the artificial neural network, respectively, to predict drying characteristics. The artificial neural networks were developed with various parameters, including activation function, sampling type, split ratio, number of neurons and epoch number. The optimal model provided the root mean squared error of 0.111 and the coefficient of determination of 0.999. The best prediction was observed in the model using rectifier activation function with a split ratio of 0.85, epoch number of 1800, and 50 and 90 neurons in the first and second hidden layers, respectively.

Investigation of drying with ultrasonic pretreatment on the chemical composition of the essential oil from Cyperus rotundus L. tubers

Drying is an important step, as it extends plant durability and delays the development of undesirable microorganisms. However, depending on the drying method, conditions involved and plant species, changes can occur in the plants, which can improve or reduce their medicinal properties. Ultrasonic pretreatment has the advantage of facilitating water migration into the cells, improving the drying rate. In this context, the objective of this study was to evaluate the influence of different drying temperatures associated with ultrasonic pretreatment, on the chemical composition of the essential oil from Cyperus rotundus L. tubers. The assays were conducted according to a Central Composite Rotational Design (CCRD), considering two factors with the following ranges: duration of the ultrasonic bath from 0 to 40 minutes, drying air temperature from 40 to 70 ºC. The essential oil was extracted by hydrodistillation and its constituents were identified by gas chromatography coupled to mass spectrometry (GC–MS). Twenty-four compounds were identified in C. rotundus essential oil, corresponding to more than 70% of the total peak areas resulting from the chromatographic reading. In the twelve drying treatments evaluated, the compounds 3,4-dimethyl-3-cyclohexen-1-carboxaldehyde, caryophyllene oxide and α-cyperone were found at higher concentrations (between 17.85-25.38%; 17.27-25.26%; 4.95-11.34%, respectively) in eleven; in treatment 11, the major compounds were caryophyllene oxide (23.40%), 3,4-dimethyl-3-cyclohexen-1-carboxaldehyde (21.5%) and humulene (8.41%). At high temperatures and long ultrasonic times, a lower quality of C. rotundus essential oil was observed. The best results were obtained at intermediate ultrasonic bath temperatures and times, where there was an improvement in quality compared to fresh tubers (control).

Effect of microwave pretreatment on truffle solar drying from an energetic perspective

AbstractDrying, an age‐old method of food preservation, involves the concurrent exchange of heat and mass, resulting in reduced moisture content. The current study is based on experimental approach to evaluate the impact of combined microwave and solar drying on the drying kinetics and the energy efficiency of truffle drying. This study explores the impact of a 4‐min microwave pretreatment on the solar drying of truffle slices. The findings demonstrate that microwave treatment significantly reduces the time required for solar drying. When compared to solar drying without pretreatment, microwave treatment leads to a reduction in drying time ranging from 23.07% to 70.37% at temperatures between 50 and 80°C. The Midilli–Kucuk model is employed to elucidate the experimental results, revealing strong fits with high correlation coefficients and low standard error values. Microwave pretreatment enhances the drying rate of truffle slices, resulting in a higher effective moisture diffusivity compared to untreated slices. The activation energy for drying also decreases from 76.37 to 25.25 kJ/mol after microwave pretreatment. An energy analysis of the drying process underscores that elevating the drying air temperature reduces energy consumption. Furthermore, the proposed microwave pretreatment influences the energy efficiency of the drying process.

Warm Air Delivery in Adhesive Application: Effect on Bonding Performance and Morphological Outcomes.

Solvent evaporation within an adhesive layer is a crucial step during a bonding process. The aim of this current research was to test whether the use of different air temperatures (20 °C, 40 °C, and 60 °C) for solvent evaporation improves the performance of four adhesive systems to dentin. Sixty non-carious human molar teeth were randomly prepared for micro-tensile bond strength (μTBS) tests. Four different adhesive systems, Prime&Bond Universal (PBU), OptiBond Universal (OBU), OptiBond FL (OBFL), and Clearfil SE (CSE), were applied following the manufacturer's instructions. Three groups based on the air-drying temperature were used: solvent evaporation was performed with either of warm (40 °C), (60 °C), and cold air as control group (20 °C) for 10 s at a distance of 5 cm. In all bonded surfaces, three resin composite (Reflectys, Itena Clinical, Paris, France) layers of 2 mm thickness were built up. The resin-dentin samples were kept in distilled water at 37 °C for 24 h and 6 months, respectively, before μTBS testing. Failure analysis, scanning electron microscopy of resin-dentin bonded interface, and solvent evaporation rate were tested as secondary variables. All analyses were conducted using a significance level of α = 0.05. Bond strength (BS) values were similar among all the adhesive systems used (p > 0.05). Also, the aging factor did not affect the BS (p > 0.05). Only the factor of temperature used for solvent evaporation resulted in a statistically significant effect (p < 0.05), with the temperature of 60 °C being the highest value (p < 0.05). A failure mode evaluation revealed mostly adhesive or mixed modes of failures in all the different temperatures of air used for the solvent evaporation of each adhesive system. The thickness of the adhesive layer and the creation of resin tags varied amongst the temperatures evaluated. For all adhesive systems tested, the use of 40 °C or 60 °C air for solvent evaporation led to an increased mass loss. Warmer temperatures for solvent evaporation contributed positively to bonding performance, enhancing both the quality of the adhesive layer and its interaction with the dentin tissue. Optimizing solvent evaporation with warmer air temperatures (40 °C and 60 °C) significantly improved µTBS, offering a practical means to enhance the quality and longevity of adhesive restorations in esthetic dentistry.

A hybrid digital shadow to assess biological variability in carrot slices during drying

Digital twins allow non-invasive access to the hygrothermal processes of fruits and vegetables during drying. However, existing methods do not consider the heterogeneity of product particles throughout the process. This study uses physics-based and Monte Carlo simulations to predict natural variability in carrot slices from raw material to the final product. Data from literature to model sorption isotherm and effective diffusivity, to validate the hygrothermal model, and to provide input ranges for Monte Carlo simulations was used. Nusselt correlations define heat and mass transfer coefficients, while conductive heat transfer accounts for thermal contact between the mesh tray and carrot slice. Validation shows good agreement between model and experimental data. A first-order reaction kinetic describes the thermal decay of β-carotene satisfactorily. Sensitivity analysis identifies the parameters that impact drying time and carotene retention most: slice thickness and initial moisture content. The study also introduces a water activity assessment method for the carrot slice population in the dryer, applying it to assess convective drying efficiency under different conditions. Raising the drying air temperature from 50 °C to 70 °C, along with a shift to product temperature-controlled drying, achieves a 45 % reduction in drying time, a 27 % decrease in required heat energy, and an 8 % improvement in β-carotene retention. The described approach holds promising insights for optimizing drying processes without additional equipment. In addition, the combination of physical and Monte Carlo simulations will enable progress in areas where variability plays a decisive role.

Influence of drying with ultrasound+ethanol pre-treatment on the chemical composition of the essential oil from ripe fruits of S. terebinthifolius

The aim of this study was to evaluate the influence of different drying temperatures associated with ultrasound+ethanol pre-treatment on the chemical composition of the essential oil from ripe fruits of S. terebinthifolius. The experiments were conducted using a Central Composite Design, considering two factors within the following ranges: duration of ultrasound+ethanol pre-treatment from 0 to 12 minutes, drying air temperature from 40 to 80 °C. The essential oil was extracted by hydrodistillation, and its constituents were identified by gas chromatography-mass spectrometry (GC-MS). In the essential oil of S. terebinthifolius, five compounds were identified, accounting for over 80% of the total peak areas from the chromatographic analysis. Applying different pre-treatment times combining ultrasound and ethanol, along with different drying temperatures, resulted in qualitative changes in the chemical composition of the essential oil of S. terebinthifolius. The most satisfactory results were achieved at drying air temperatures of 50 °C and 70 °C, with shorter ultrasound+ethanol pre-treatment times. Additionally, it was observed that longer ultrasound+ethanol pre-treatment times (12 minutes) led to a reduction in the quality of the essential oil of S. terebinthifolius.

Literature review: use of ultrasound and ethanol as pre-treatment in the drying of vegetable products with bioactive compounds

Despite the broad therapeutic action of plant species with bioactive compounds and drying being the most recommended operation for maintaining the quality of various plant materials, the fact that these materials differ in terms of moisture content, chemical composition, and morphology makes the optimization of drying methods and parameters for each species essential tools for obtaining dried plant biomass of high commercial value. The use of ethanol as a pre-treatment for drying, through immersion, allows for the modification of the product's natural structure and improves moisture transfer, consequently increasing the drying rate (KOMPANY et al., 1990). Ultrasonic waves can increase the availability of energy and accelerate mass transfer processes in the product, preserving its main qualitative attributes without significantly raising the drying air temperature (O’DONNEL et al., 2010). Therefore, this review aimed to elucidate the use of ultrasound and/or ethanol pre-treatment in the drying of various medicinal plant species, exploring their mechanisms of action and addressing their main effects on the desorption process and the chemical composition of these materials.

Intermittent drying of Lippia origanoides: influence of the process on the quality of the extract and energy consumption

This study investigated the effect of intermittent drying on the specific energy consumption, plant extract yield, content of phenolic compounds, flavonoids, and antioxidant activity of L. origanoides leaves. Drying tests were carried out at the Postharvest Laboratory of Medicinal, Aromatic and Spice Plants of the Agricultural Engineering Department of the Federal University of Viçosa, Viçosa, MG, Brazil (20 ° 46 '13, 5 ”S; 42 ° 52 ' 23.3 ”W, and 645 m altitude) in June 2019. The experiment was conducted using a 3 × 4 factorial scheme matching three drying temperatures (50, 60 and 70 °C), with two drying methods: drying continuous and intermittent drying (with three intermittent ratios between drying and resting in minutes: 10/20, 15/15 and 20/10). The design used was completely randomized and with three replications. Drying with a 10/20 intermittency ratio reduced the specific energy consumption during the drying of L. origanoides leaves at 50 and 70 °C. The application of the 10/20 intermittency ratio maximized the yield of plant extract during the drying of the leaves of L. origanoides at 60 and 70 °C. Drying with a 10/20 intermittency ratio maximized the content of total phenolic compounds and total flavonoids at all evaluated drying air temperatures. Intermittent drying did not significantly affect the antioxidant activity of the plant extract of L. origanoides leaves.

Effect of Air Temperature and Velocity on Listeria monocytogenes Inactivation During Drying of Apple Slices

A wide range of drying parameters and methods are used by industry to produce dried apples. To ensure end-product safety and regulatory compliance, it is essential to evaluate the effectiveness of such industrial practices on microbial inactivation. Therefore, the objective of this study was to evaluate the effects of drying air temperature and velocity on Listeria monocytogenes inactivation during drying of apple slices. Apples (cv. Gala) were cored, sliced as rings (∼6 mm thick), and surface-inoculated with broth-grown culture of an 8-strain cocktail of L. monocytogenes to achieve an inoculation level of 8.6 ± 0.3 log CFU/g. Apple rings were dried in batches using dry air in a pilot-scale impingement oven at 60 or 80 °C air temperature and 0.7 or 2.1 m/s air velocity, and sampled every 30 min for bacterial enumeration, water activity (aw), and moisture content analysis. L. monocytogenes reduction increased (P < 0.05) with higher air velocity or higher drying air temperature. By the end of drying, in which the standard moisture content for dried apple slices of <24% wet basis was reached, L. monocytogenes was reduced by 1.8 ± 0.3 and 2.8 ± 0.7 log CFU/g at 0.7 and 2.1 m/s air velocity, respectively, after 180 min at 60 °C. When using 80 °C drying temperature, L. monocytogenes reduction was 5.2 ± 0.5 log CFU/g at both air velocities after 150 min. Therefore, process conditions should be considered in the validation of fruit drying processes, instead of solely relying on product endpoint properties, such as moisture content.

Performance Evaluation of Two Stages Parallel Flow Indirect Evaporative Cooling with Aspen Pads in Baghdad Climate Conditions

This study delves into the realm of advanced cooling techniques by examining the performance of a two-stage parallel flow indirect evaporative cooling system enhanced with aspen pads in the challenging climate of Baghdad. The objective was to achieve average air dry bulb temperatures (43 oC) below the ambient wet bulb temperatures (24.95 oC) with an average relative humidity of 23%, aiming for unparalleled cooling efficiency. The research experiment was carried out in the urban environment of Baghdad, characterized by high temperature conditions. The investigation focused on the potential of the two-stage parallel flow setup, combined with the cooling capability of aspen pads, to surpass the limitations imposed by conventional cooling methods. The empirical findings underscored the capacity of the two-stage parallel flow configuration to achieve air-dry bulb temperatures surpassing the ambient wet bulb temperature. Nonetheless, it was evident that an excessive application of water (exceeding 9 lpm) onto the aspen pads within the wet channels yielded adverse repercussions on the cooler's performance metrics, specifically in terms of wet bulb effectiveness and coefficient of performance. A range of air flows spanning from 150 CMH to 350 CMH was analyzed, revealing the influence of heightened air flow rates on the resultant dry bulb temperatures delivered by the cooling system. Notably, the peak wet-bulb effectiveness registered at 1.08, concurrently yielding a coefficient of performance measuring 7.8.

Zinc Ferrite Nanoparticle Coatings on Austenitic Alloy Steel.

The phase transition of austenitic stainless steel of commercial label CL20ES and zinc ferrite nanoparticles was studied in an oxidative atmosphere of dry air to develop a low-cost, effective technique for covering-layer fabrication. CL20ES powder and zinc ferrite powder were mechanically mixed. This mixture was studied in an atmosphere of dry air at different annealing temperatures from room temperature to 900 °C. The employed characterization techniques are X-ray powder diffraction, Mössbauer spectroscopy in the transmission geometry, and scanning electron microscopy with elemental mapping. The fabricated layers were also characterized by surface-specific techniques such as conversion electron Mössbauer spectroscopy and grazing incidence X-ray powder diffraction. The analyzed powder mixture shows resistance against oxidation in dry air and high temperatures. These results were employed to produce zinc ferrite covering layers on 3D-printed cylinders of CL20ES. The results show a predisposition of zinc ferrite to be recrystallized at temperatures above 350 °C without the production of corrosive substances on steel. The zinc ferrite layers were analyzed by an ultrasonic hardness tester as well, which proved the hardness enhancement.

Convective drying of Gardenia erubescens fruits: Effect of pretreatment, slice thickness and drying air temperature on drying kinetics and product quality

Gardenia erubescens fruits are regarded as nutrient-dense, capable of promoting nutritional and metabolic human health. However, they are seasonal and highly perishable which limits their consumption and wider utilization. In this study, the effect of slice thickness (3 mm and 5 mm), pretreatments (steam blanching and dipping in ascorbic acid solution) and drying air temperature (40 °C, 50 °C, 60 °C and 70 °C) on drying kinetics, color, β-carotene and vitamin C content of Gardenia erubescens fruits were investigated. The results showed that the drying time increased as slice thickness increased, and decreased as drying air temperature increased but did not follow any trend for pretreatment. The Page model (R2 values of 0.9998–0.9999) exhibited the best fit to the drying kinetics data. The diffusivity values (5.31 × 10−11 to 4.14 × 10−10 m2s−1) increased as the slice thickness and drying air temperature increased but had no linear trends with pretreatment. The activation energy ranged from 14.35 to 44.78 kJmol-1, with the highest being recorded by 5 mm untreated samples and the lowest by the 3 mm blanched samples. The total color change (ΔE*) of the samples generally decreased as the drying air temperature increased but increased as the slice thickness increased. The ascorbic acid pretreated samples had the least color change, followed by the untreated samples while the blanched samples had the highest change. Overall, the 5 mm ascorbic acid pretreated samples dried at 70 °C had the least color change (13.33 ± 0.52). The blanching and dipping in ascorbic acid solution generally yielded lower β-carotene and vitamin C values as compared to the untreated samples. The 3 mm ascorbic acid pretreated samples dried at 50 °C recorded the lowest β-carotene (42.70 ± 3.21 μg/100 g) while the 5 mm ascorbic acid pretreated samples had the lowest vitamin C (37.50 ± 2.65 mg/100 g) at 70 °C. Pretreatments and drying air temperatures showed mixed effects on the drying characteristics, color, β-carotene and vitamin C contents of fruit slices. The findings, therefore, indicate that a compromise may have to be made on the aforementioned processing conditions in order to meet the desired attributes of one's interest.

Drying kinetics of rice using a flatbed dryer with a hot air source from a biomass waste pyrolysis reactor

This study aims to evaluate the process of rice drying using a flatbed dryer integrated with a biomass waste pyrolysis reactor as a heat supplier. The integration of dryer equipment with pyrolysis reactor aims to replace the use of fossil fuel energy with biomass as an eco-friendly source and abundantly available in nature. The current investigation assessed how tray height and drying temperature affected rice’s moisture ratio, drying rate, and drying characteristics. The drying air temperature of 70°C and the tray height of 40 cm were found to yield the optimum drying outcomes, according to the results. The best drying kinetics model that can describe the rice drying process is the Page model.