Drying Of Slices Research Articles

Effect of slice thickness and hot-air temperature on the kinetics of hot-air drying of Crabapple slices

This study was investigated the effects of hot-air temperature and slice thickness on drying characteristics of Crabapple slices. Drying experiments were carried out in the ranges of 60-90 °C. The thickness conditions of Crabapple slices for thin layer drying were 3mm and 5mm. The increase in the temperature of the hot-air and the decrease in the thickness of the slicing causes the drying time to be significantly shortened. Fick’s diffusion model was applied to describe the water transfer of the Crabapple slices, and the effective diffusion coefficients varied from 0.6142 × 10-8m2/s to 1.9867 × 10-8m2/s in a given range of drying temperature. The effective diffusivity increases with increasing temperature. The activation energy values of Crabapple were 17.46 and 23.82 kJ/mol for the thickness of 3 and 5 mm, respectively. The Page model was revealed to be a better fit to describe the drying curve of Crabapple compared to other models.

Evaluation of high temperature-vacuum application periods during conventional drying of mushroom slices

Evaluation of high temperature-vacuum application periods during conventional drying of mushroom slices

Experimental investigation on drying of tomato slices

Experimental investigation on drying of tomato slices

Experimental and numerical study on the shrinkage-deformation of carrot slices during hot air drying

In order to further understand the mechanism of material volume change in the drying process, numerical simulations (considering or neglecting shrinkage) of heat and mass transfer during convective drying of carrot slices under constant and controlled temperature and relative humidity were carried out. Simulated results were validated with experimental data. The results of the simulation show that the Quadratic model fitted well to the moisture ratio and the material temperature data trend with average relative errors of 5.9% and 8.1%, respectively. Additionally, the results of the simulation considering shrinkage show that the moisture and temperature distributions during drying are closer to the experimental data than the results of the simulation disregarding shrinkage. The material moisture content was significantly related to the shrinkage of dried tissue. Temperature and relative humidity significantly affected the volume shrinkage of carrot slices. The volume shrinkage increased with the rising of the constant temperature and the decline of relative humidity. This model can be used to provide more information on the dynamics of heat and mass transfer during drying and can also be adapted to other products and dryers devices. Keywords: carrot drying, numerical simulation, heat, and mass transfer, shrinkage DOI: 10.25165/j.ijabe.20231601.6736 Citation: Jiang D L, Li C C, Lin Z F, Wu Y T, Pei H J, Zielinska M, et al. Experimental and numerical study on the shrinkage-deformation of carrot slices during hot air drying. Int J Agric & Biol Eng, 2023; 16(1): 260–272.

Optimizing carrot slices drying: A comprehensive study of combined microwave and convective drying

The integration of both microwave and conventional convective drying techniques (MCD) has notably boosted the efficiency and effectiveness of carrot slice drying. This combination has led to improvements in energy utilization without harmful influence on the quality of the dried carrots. The shortest dehydration time (20 ± 1 min) and the lowest energy consumption (0.220 ± 0.011 kWh), as well as the lowest water holding capacity (705.88 ± 4.97 g H20 g dm-1), had the model of carrot slices dried on 15 seconds of microwave drying on 900W, and 7 seconds of convective drying on 180 °C. The color modification, particularly the change in pigment concentration from its natural state in fresh carrots, was a result of employing the MCD method. The drying time had no impact on color pigment characteristics, unlike the energy model. The values of red, gree and blue color are the highest for the of carrot slices dried on 9 seconds of microwave drying on 900W, and 12 seconds of convective drying on 200°C.

Drying of mushroom slices in a new type solar drying system and under open sun: Experimental and mathematical investigation

Drying is among the beneficial food preservation strategies and this method ensures food products last before they reach consumers. The most used drying method is direct drying under the sun. However, in this method, the negative effects of the external environment damage food products. Recently, solar drying systems have been the main subject of much research as they have been protecting food from the negative effects of the external environment. In this study, a solar drying system (SD), which have a drying chamber with different structure, was used for drying mushroom. At the same time, mushroom slices were dried under open sun (OSD) for observing the performance of drying system. Drying rate (DR) and moisture ratio (MR) values were determined from the experiments. In addition, the MR values obtained from the experiments were estimated by 6 different mathematical models and 6 different machine learning algorithms. According to the results of the experiments, the drying time of the mushroom slices using SD was approximately 12.4 hours less than the drying time under open sun. The best convergence in the results gathered from the mathematical models is Sripinyowanich and Noomhorn and Hii et al. models for SD and OSD, respectively. The best estimation for MR values was realized by the Multilayer Perception algorithm for both drying methods.

Thermoultrasound and microwave-assisted freeze-thaw pretreatments for improving infrared drying and quality characteristics of red dragon fruit slices.

The effects of thermoultrasound (US-FT), microwave (MW-FT), and room temperature (RT-FT) freeze-thaw pretreatments were evaluated for improving drying kinetics and quality during infrared drying (IRD) of red dragon fruit slices (RDFS). Results indicated that microstructural alterations induced by the different pretreatments improved the moisture removal rate and effective diffusivity, and significantly reduced the drying time. US-FT pretreatments prompted more efficient drying and presented an overall enhancement in the quality of RDFS, particularly at low temperatures of 25 and 50 ℃, while enhancements in TFC, FRAP, and CUPRAC were associated with RT-FT. High-power (500 W) MW-FT pretreatments improved colour and structural properties, while low-power (100, 300 W) improved TPC, TFC, ascorbic acid, betalains, and antioxidant activity. Overall, cellular and chemical alterations prompted by pretreatments improved the drying process but presented adverse effects on betaxanthin. The study presented the fundamental background for improving the IRD of foods from the use of improved thawing approaches during freeze-thaw pretreatments.

Infrared drying of apple (Malus domestica) slices: Effect on drying and color kinetics, texture, rehydration, and microstructure

AbstractIn this study, apple slices were dried using infrared (IR) and hot air techniques and comprehensively analyzed in terms of drying and product characteristics. The influence of IR power level (450–650 W) and hot air temperature (60–75°C) on mass transfer, color kinetics, product texture, microstructure, and rehydration characteristics was studied. The results indicated that drying time, color change, and energy requirement were lower in IR drying than in hot air drying. Moisture diffusivity was observed to increase with IR power (3.367 × 10−9–5.579 × 10−9 m2/s) and hot air temperature (1.288 × 10−9–2.387 × 10−9 m2/s). The activation energies of apple slices in IR and hot air drying were 11.94 and 21.90 kJ/mol, respectively. IR‐dried apple slices were more crispy, with a porous structure and higher rehydration ability. Experimental data were fitted to nine different thin‐layer drying and four‐color kinetic models using nonlinear regression analysis. The results of regression analysis indicated that the Midilli–Kucuk model is the best model to describe the drying behavior in both techniques. The color characteristics (L, a, and b) can be best explained by the modified color model and total color change by fraction conversion model for both IR and hot air drying of apple slices. This study revealed that IR drying of apple slices results in a better quality product in less time and energy as compared to hot air drying.Practical applicationsDrying is a vital food processing and preservation technique based on the principle of reducing the water content of the product. Although several drying techniques are available, there have been continuous efforts to improve drying methods in terms of energy efficiency and product quality attributes. The present work has been carried out considering the dearth of information on the influence of infrared power/intensity on the drying behavior and product quality of apple slices. Mass and color kinetics have been studied for a better understanding of the process, along with texture, microstructure, and rehydration properties. Our results showed that the process is superior, in terms of energy and product quality, as compared to other published work. It is concluded that infrared drying can be effectively used in the dehydration of apple slices on an industrial scale and can be promoted as a healthy alternative to fried snacks.

A Prototype Passive Solar Drying System: Exploitation of the Solar Chimney Effect for the Drying of Potato and Banana

Agricultural product drying is of great importance as it is a reliable method for fruit and vegetable preservation. Tackling the high energy consumption of the process will reduce the final product cost and mitigate greenhouse gas emissions. In this work, a passive drying method was experimentally evaluated. The method was based on the principle of the stack effect taking place in the solar chimney structure. Different types of solar chimneys in terms of dimensions and materials were evaluated for the drying of banana and potato slices. The results of the experiments showed that the drying rate was close to solar drying systems. Parameters such as height and material characteristics of drying tubes, as also weather conditions, influenced the drying rate. It was found that the banana and potato slices were dried at a satisfactory rate for almost 48 h during the summer period in Greece. From the parameters of the drying tubes that were varied, it was found that both the height and material played a major role, as did the air flow rate. With the increase in the drying tube by 1 m and with the choice of proper manufacturing material, an increase in the flow rate between 40% and 100% can be achieved. When only the color of two 3 m-high tubes changed, the flow rate varied between 4% and 15%. The proposed method has almost zero energy consumption, and it could be used as a standalone or as a part of a hybrid drying system. It can also be adjusted in existing greenhouse-type agricultural structures as a parallel operation system.

An experimental investigation on a locally fabricated dryer integrated with a novel solar air heater for the drying of potato slices

ABSTRACT Typical fuel-driven commercial dryers have excellent efficiency with homogeneous high-quality output, but they are beyond the access of farmers with limited agro land and financial resources. In this study, drying trials with potato slices were carried out utilizing a laboratory scale built drier coupled with an unique solar air heater. Assuming the set-up as mixed mode type solar dryer, performance of the dryer during the drying of potato slices was studied and the results were compared with that of open sun drying (OSD). The novel two pass solar air heater used in this project has aluminum turbulators arranged in staggered fashion. The absorber plate with aluminium turbulators present inside the double pass solar air heater reached a maximum temperature of 68°C. The average efficiency of the novel solar heater was about 72%. The moisture content of potato was reduced to 18.23% in 8 hours from 82.15%. The maximum thermal efficiency of the dryer was determined as 34%.The average specific energy requirement was estimated as 1.61 kWhkg−1 and the shrinkage ratio was found to be 0.2 at the end of 7 hours.

Effect of Sun Drying on Osmotic Dehydration of Beetroot (Beta vulgaris L.)

An Experiment was conducted at the Postharvest laboratory, Department of Horticulture entitled with “Effect of osmotic dehydration of beetroot (Beta vulgaris L.) under sun drying” during the year 2021-2022 to determine the effect of sun drying on osmotic dehydration of beetroot slices for its evaluation of physio-chemical contents, shelf life, and sensory evaluation during total 60 days of storage period and to work out on the economics In this study, 10 treatments with varying amounts of salt, honey, sugar, and K2S2O5 were used, with 4 replications (10 days, 30 days, 45 days, and 60 days) of storage periods at ambient temperature. On the basis of results obtained during the investigation the best osmotic agent for drying of beetroot slice was T7 Treated beetroot slices (Sugar 200g/Kg + K2S2O5 0.5%) + Sun drying of beetroot slices) with pH (6.30), TSS (11.46), fat content (0.28), Protein content (2.41), weight (92.5g). T7 (Treated beetroot slices (Sugar 200g/Kg + K2S2O5 0.5%) + Sun drying of beetroot slices) was found to have the highest value for reducing sugar content, Flavour and Taste score, and overall acceptability. Treatment T7 also had the highest benefit-cost ratio (1.94).

Energy, economic analysis and mathematical modelling of mixed-mode solar drying of potato slices with thermal storage loaded V-groove collector: Application to Maghreb region

This research aims to study the thermodynamic and economic feasibility of a mixed-type solar dryer of potato chips equipped with a V-corrugated solar collector and loaded with a heat storage system in the Maghreb region of North Africa. The thermodynamic, economic assessment and environmental impact of deploying the solar dryer were investigated. For, this reason a mix-mode solar dryer with V- groove collector loaded with granite bed as thermal storage was developed at the Faculty of Sciences and Techniques of Tangier, Morocco. Drying of the potato chips took 4.5 h at a collector efficiency of 60.08%. Solar radiation heat contributed 78.18% of energy utilization while the granite bed thermal storage contributed 21.82%. The effectiveness of energy utilization embodied in specific energy consumption was determined as 6.109 kWh/kg and the specific moisture extraction rate was deduced as 0.1637kg/kWh. Wang/Singh and Midilli/Kucuk models presented the best kinetic models for predicting the potato drying kinetic in the mixed-type dryer and open sun drying, respectively. Using the solar dryer in the Maghreb country of Morocco can save $69.58 to $698.5 on running costs with a payback period of 0.179–1.744 years at a usage rate of 10–100%. Environmental impact assessment showed the dryer can limit up to 163 tons of CO2 from the atmosphere at the current usage.

Influence of far‐infrared vacuum drying on drying kinetics and quality characteristics of Cistanche slices

AbstractIn order to improve the drying efficiency and quality of Cistanche, the effects of far‐infrared vacuum drying on drying rate, active component content and microstructure of Cistanche slices were studied with drying temperature, slice thickness and irradiation height as experimental indexes. The results showed that the drying process of Cistanche was mainly concentrated in the deceleration stage. When the drying temperature was 55°C, the slice thickness was 4 mm, the irradiation height was 150 mm, and the time to reach the safe water content (10% w.b.) of Cistanche was the shortest. With the increase in drying temperature, slice thickness and irradiation height, the contents of phenylethanoid glycosides, iridoids, polysaccharides, total phenols and total flavonoids in dried products increased first and then decreased. Compared with natural drying, the samples dried by far‐infrared vacuum have more pores and better structural integrity. Phenylethanol glycosides and iridoid compounds, such as echinacoside and verbascoside, in Cistanche have significant effects in anti‐inflammatory and analgesic, tonifying kidney yang, anti‐Alzheimer's disease and protecting various organs and systems of the body. In this study, the slices of Cistanche were processed by far infrared vacuum drying, and the effects of different drying conditions on drying rate, effective moisture diffusion coefficient, active ingredient content, antioxidant activity, color and microstructure of dried Cistanche were studied. The drying process was fitted by a drying model, in order to obtain dried Cistanche products with better quality, and provide theoretical basis and technical support for the actual production of Cistanche.Novelty impact statement Midilli model could better describe the variation law of water content in the drying process of Cistanche. Compared with natural drying, the surface samples dried by far‐infrared vacuum have no cracks and good boundary integrity. The optimal process parameters (55°C, 4 mm, 310 mm) for far‐infrared vacuum drying of Cistanche slices were determined by the entropy value method.

Performance evaluation, morphological properties and drying kinetics of untreated Carica Papaya using solar hybrid dryer integrated with heat storage material

In developing country like India, renewable energy plays a vital role in extending technology for the farmers to enhance the agricultural productivity. The aim of the present work is to demonstrate the impact of heat storage material (HSM) in solar drying of untreated Carica Papaya slices using evacuated tube collector (ETC) based photovoltaic thermal (PVT) hybrid solar dryer. The performance of the solar dryer with gravel rock bed as HSM is compared with the solar dryer without HSM and natural sun drying. The initial moisture content of papaya slices is found to be 83 % (wb). The safe moisture content was attained in 5 h using solar dryer integrated with HSM, whereas, it took 6 h and 11 h in solar dryer without HSM and sun drying respectively. The inclusion of HSM increases the drying potential thereby reducing the drying period substantially. According to the statistical analysis of the results, Midilli et al. model was found to be the most suitable model to describe the drying kinetics of papaya slices in solar dryer with HSM, solar dryer without HSM and sun drying. The effective moisture diffusivity is found to be 2.58346 × 10−8 m2/s, 4.7366 × 10−8 m2/s and 6.15303 × 10−8 m2/s for sun drying and solar drying without HSM and solar drying with HSM respectively. The activation energy of untreated papaya slices is accounted to be 37.7441 kJ/mol using the Arrhenius equation. The findings proved that the solar dried papaya in dryer with HSM is observed to be better preserved without losing size, shape, colour, appearance, texture, flavour and quality than the solar dried papaya in dryer without HSM and the sun-dried papaya. The economic evaluation of ETC based PVT hybrid solar dryer with HSM reveals that the payback period is 2 years which is very low as compared to the life span of 25 years.

Drying and rehydration kinetics of peeled and unpeeled green apple slices (Granny Smith cv)

In this work, the kinetics of drying and rehydration of green apple slices peeled and unpeeled (Granny Smith cv) were studied. The apple slices were dried at 50, 60, and 70 °C, and after that, rehydrated at ambient (Ta ) and boiling temperature (Tb ). The drying kinetics were adjusted with the Dincer and Dost model, giving a good fit. Effective diffusivity (Deff ) and the convective mass transfer coefficient (hm ) were also determined, both coefficients increase with drying temperature, being 1.25 × 10−9 m2 s−1 and 9.53 × 10−7 m2 s−1 the highest values obtained for the peeled apple slices respectively. Peleg and Weibull models were adjusted to the rehydration experimental data obtaining a good fit (R 2 > 0.99). Deff values increase significantly with rehydration temperature but take similar values between peeled and unpeeled samples. Acidity, pH, moisture content, solid soluble content, and equivalent diameter were determined to compare the fresh apple slices with those after dehydration and the post-rehydration process. The apple slices rehydrated at boiling temperature better preserved the characteristics of fresh samples due to the short immersion times in water, no significant differences were observed between peeled and unpeeled apples. According to the results, it is convenient to dry the apple slices unpeeled at 70 °C and rehydrate them at Tb .

Thermal performance enhancement in hot air and solar drying of pineapple slices with ultrasonic vibration

Hot air and solar drying are among the most popular preservation methods for fresh fruits. Ultrasonic technology could enable a faster dehydration rate at low temperatures, hence, preserving vitamins and nutrients in fruits. In this work, the application of ultrasonic vibration to pineapple drying was investigated. Experiments were conducted in hot air as well as direct solar dryers. The temperature in the hot air dryer was controlled at 60 °C, with an applied vibration frequency of 40 kHz. Three cycles of 10, 20, and 30 min with 1 min ultrasonic operation per interval were tested. The results showed that for the cycle of 10 min with 1 min vibration applied, the moisture content of pineapple slices was decreased from 87 to <13.7 %wb at a maximum evaporation rate of 49 g/h. Similar tests in the solar dryer proved to reduce the drying time from 3 to 2 days, with an increased evaporation rate of 10.6 g/h. Minimum specific energy consumption was realized by applying 1 min of ultrasonic vibration in a 10 min cycle with the solar dryer. Maximum thermal efficiency of over 63% was achieved with ultrasonic assisted solar drying.

Prediction of moisture ratio and drying rate of orange slices using machine learning approaches

In order to improve the drying characteristics and to optimization of drying conditions, machine learning (ML) and response surface methodology (RSM) were applied in air-convective drying of orange slices (Washington Navel and Valencia cultivars). Interactions of temperature (T, 50–60°C), sample thickness (ST, 5–9 mm), and drying time (DT, 8–10 h) like independent variables with specific moisture extraction rate, effective moisture diffusivity, energy efficiency, and energy consumption like dependent variables were determined. In addition, five machine learning algorithms (random forest-RF; artificial neural network-ANN; gaussian processes-GP support vector regression-SVR, and k-nearest neighbors-kNN) were used to predict moisture ratio and drying rate. In Washington Navel and Valencia cultivars, the greatest correlation coefficients (R) for prediction of moisture ratio were obtained k-NN algorithm with values of 0.9944 and 0.9898, respectively. Also, drying rate prediction results showed that k-NN achieved higher R with values of 1.0000 and 0.9954, respectively. Experimental findings were adapted by a second-degree polynomial model through variance analysis to identify model fitness and optimal drying conditions. Combined desirability value was calculated as 0.8812 for Valencia and 0.8564 for Washington. Increasing energy consumption was encountered with increasing drying time and sample thickness. Besides, energy consumption had a decreasing trend at higher temperatures. Practical applications Machine learning models are novelty and rapid methods that have been successfully utilized to solve such challenges agricultural commodities. Drying is common process to preserve the food quality. This study provides optimum conditions for drying orange slices in single unit air-convective dryer and improves the effect of drying system on some drying characteristics energy aspects. In addition, this study can be able to present a technical knowledge for orange slice drying and related equipment design.

Thin-layer drying characteristics, modeling and quality attributes of tomato slices dried with infrared radiation heating

An Infrared dryer was used to examine the drying of tomato slices. In this investigation, the influence of infrared radiation (IR) on the rate of drying, physical quality, energy combustion of tomato was estimated at three different levels of intensity at 0.15, 0.20, and 0.35 W/cm² under different air flows of 0.5, 1, and 1.5 m/s. Tomato slices were dried with an initial moisture content of 19.7 to 0.17 g water/g dry solids by infrared drying. The moisture content and drying rates are found to be dramatically affected by infrared density. An increase in the drying rate and a decrease in the drying period occurred with increasing infrared intensity. A decrease in energy consumption was detected with the increase of radiation intensity. The results clarified that the shrinkage ratio increased with increasing infrared intensity. The rehydration ratio raised with the increase in radiation intensity. The change in the colour difference of dried slices increased with an increase in radiation intensity. The models were in comparison using (R²) coefficient of determination, modelling efficiency (EF), and (χ²) reduced chi-square. Midilli model was fit for simulation of all drying conditions and could be used to estimate tomato moisture content at any time during the infrared drying process.

Numerical simulation of contact vacuum drying of potato slices

• A mathematical model for contact vacuum drying is numerically solved. • The simulations predict the drying kinetics coupled to the pressure changes in the chamber. • The frequency of active/passive phases depends on the mass flux, which is linked to the free moisture content of the samples. • Vacuum drying reveals to have a larger impact in the first period of drying. In this work, a mathematical model is proposed to simulate the Contact Vacuum Drying of potato slices. Three temperatures were analyzed: 55, 65, and 75 °C with three levels of vacuum pressure: 60, 40, and 20 mmHg. In the macroscopic model, the boundary condition for the moisture conservation is written in terms of water vapor pressure, and it considers the dynamics of the vapor pressure in the chamber. The simulations predict the evolution of gas pressure and the drying kinetics. As drying occurs, the passive regime is prolonged as a result of a decrease in the moisture content. The maximum drying rate (1.4 E-3 kg. water/kg. dry solid·s) corresponds to the drying condition at 75 °C and 20 mmHg, which is the most intensive drying condition. The comparison between the predicted and experimental values showed acceptable agreement. The simulations correctly represent the drying kinetics and the evolution of the gas pressure in the drying chamber.

Development of phase change material assisted evacuated tube solar dryer: Investigation of thermal profile, drying characteristics, and functional properties of pumpkin slices

The present work aimed to develop a phase change material-assisted evacuated tube solar dryer (PCM-ETSD) and experiments were performed with and without PCM for drying pumpkin slices. Thermal performance, drying characteristics, and quality attributes were analyzed with and without PCM at different airflow rates: 34.64 kg/h, 51.96 kg/h, and 69.28 kg/h. The average temperature elevation between the ambient and drying chamber was achieved at 29.62 °C to 36.33 °C and 25.64 °C to 28.93 °C without and with PCM-assisted drying respectively. PCM-ETSD extended the drying period by 2 h and maintained the temperature ranges from 50.78 °C to 61.29 °C after sunshine hours. The PCM-ETSD reduced the moisture content of pumpkin slices by 4–5% and 8% more as compared to without PCM and sun drying respectively. Drying rate and effective moisture diffusivity are enhanced with the increase of airflow rate in the drying process and higher without PCM-assisted drying followed by PCM and sun drying. The total phenolic content and total flavonoid content are higher in PCM-assisted drying and continuously decreased with the increases in airflow rate in both drying processes. Antioxidant activity and total carotenoid content are higher in PCM-assisted drying. FTIR analysis confirmed the presence of active functional groups and phenols in dried pumpkin. The inferior color changes were observed in PCM-assisted drying of pumpkin slices. The developed PCM-ETSD could be capable of drying other food commodities on a pilot scale after sunshine with retention of quality attributes.