Review of leaf drying: Mechanism and influencing parameters, drying methods, nutrient preservation, and mathematical models

Babu, A. K.; Kumaresan, G.; Raj, V. Antony Aroul; Velraj, R.

doi:10.1016/j.rser.2018.04.002

Cited by 239 publications

(182 citation statements)

References 87 publications

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“…This is usually the longest period of drying operation. Constant rate period was observed only in a few cases [2].…”

Section: Introductionmentioning

confidence: 90%

“…The initial moisture content has to be reduced up to 7 % to 10 % to obtain the desired final moisture content [2]. When the weight of the sample becomes constant, the experiment is stopped.…”

Section: Methodsmentioning

confidence: 99%

“…There are some disadvantages associated with the open-air sun drying of Amaranth leaves, which are related to the contamination with impurities, such as airborne dust, soil, sand particles and insects. Also, the process is weather-dependent, and accompanied by bleaching due to ultraviolet (UV) and chlorophyll depletion [2]. The drying process also involves a lot of material handling and manual labour, and the drying time can be quite long.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigations of Thin-layer Drying of Leaves in a Heat-Pump Assisted Tray-type Batch Drying Chamber

Babu¹,

Kumaresan

Raj³

et al. 2020

SV-JME

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The design of a batch drying chamber with multiple trays for the thin-layer drying of fragile, heat-sensitive food materials, such as edible leaves, is a challenging task. It is essential to ensure good air distribution with minimum pressure drop in all the compartments of the drying chamber to obtain uniform drying of the product. In the present work, a drying chamber that was optimized from different configurations using computational fluid dynamics (CFD) software was fabricated and tested in the heat pump dryer. The experimental investigation was carried out with an optimized configuration for the temperature range of 50 ºC to 60 ºC, the relative humidity range of 20 % to 12 %, and air velocities of 1.41 m/s, 2.39 m/s, and 3.24 m/s. These optimal operating conditions were chosen based on an extensive literature survey on leaf drying. It was found that the drying process took place only in the falling rate period, fully controlled by the mechanism of liquid diffusion. The effects of air velocity on the performance parameters of the dryer were studied. Calculations based on the mean average parameters of the experimental data showed that a relatively higher heat utilization factor (0.17), moisture extraction ratio (0.375 kg/h), specific moisture extraction ratio (0.1529 kg/(kWh)), coefficient of performance (4.60), drying efficiency (76.23 %) and lower specific energy consumption (1.16 kW/kg) were obtained for a moderate drying velocity of 2.39 m/s in the heat pump drying process due to higher convection mass and heat transfer effects. Drying curves were plotted for different drying conditions and discussed. The findings were in agreement with those of many earlier research studies listed in the references section. The tested drying chamber can be used for drying all kinds of leaves in a heat pump dryer. Keywords: Amaranth leaves, batch dryer, heat pump dryer, coefficient of performance, thin-layer drying Highlights • A drying chamber optimized from different configurations using computational fluid dynamics (CFD) software is fabricated and tested in a heat pump dryer for drying Amaranth leaves. • Good air distribution with minimum pressure drop is ensured in all the compartments of the newly designed drying chamber to obtain uniform drying of the product. • The drying process of batches of spread-out material takes place only in the falling rate period. • Better results are obtained for a moderate drying velocity of 2.39 m/s in the heat pump drying process. • Air velocity, relative humidity, and the drying temperature are found to influence the rate of drying mutually. • The newly designed drying chamber is suitable for drying all kinds of leaves in a heat pump dryer.

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“…This is usually the longest period of drying operation. Constant rate period was observed only in a few cases [2].…”

Section: Introductionmentioning

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental Investigations of Thin-layer Drying of Leaves in a Heat-Pump Assisted Tray-type Batch Drying Chamber

Babu¹,

Kumaresan

Raj³

et al. 2020

SV-JME

Self Cite

View full text Add to dashboard Cite

show abstract

“…This process was selected to minimise damage to the microstructures of the leaf samples, and remove any excess moisture from the top surfaces of the leaves that would prevent the PDMS from setting. 48 Leaf Imprint Protocol. The polydimethylsiloxane (PDMS) (Sylgard 184, Dow Corning) was prepared at a ratio of 20:1 w/w, base to curing agent.…”

Section: Growth Protocol For a Thaliana Plants Grown On Culture Medimentioning

confidence: 99%

Replicating Arabidopsis Model Leaf Surfaces for Phyllosphere Microbiology

Soffe

Bernach

Remus-Emsermann

et al. 2019

Preprint

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words)Artificial surfaces are commonly used in place of leaves in phyllosphere microbiology to study microbial behaviour on plant leaf surfaces. Studies looking into individual environmental factors influencing microorganisms are routinely carried out using artificial surfaces.Commonly used artificial surfaces include nutrient agar, isolated leaf cuticles, and reconstituted leaf waxes. However, interest is growing in using microstructured surfaces mimicking the complex topography of leaf surfaces for phyllosphere microbiology. As such replica leaf surfaces, produced by microfabrication, are appearing in literature. Replica leaf surfaces have been produced in agar, epoxy, polystyrene, and polydimethylsiloxane (PDMS). However, these protocols are not suitable for replicating fragile leaves such as of the model plant Arabidopsis thaliana. This is of importance as A. thaliana is a model system for molecular plant genetics, molecular plant biology, and microbial ecology. Here we present a versatile replication protocol for replicating fragile leaf surfaces into PDMS. We display the capacity of our replication process using optical microscopy, atomic force microscopy (AFM), and contact angle measurements to compare living and PDMS replica A. thaliana leaf surfaces. To highlight the use of our replica leaf surfaces for phyllosphere microbiology, we visualised bacteria on the replica leaf surfaces in comparison to living leaf surfaces.

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“…6. The desired final moisture content of sago waste at the fluidized bed dryer outlet is selected to be 10% to preserve the nutrients of the sago waste [18]. 7.…”

Section: Assumptionsmentioning

confidence: 99%

Simulation of a Fluidized Bed Dryer for the Drying of Sago Waste

et al. 2018

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The large amount of sago waste produced by sago processing industries can cause serious environmental problems. When dried, these residues usually have a high starch content (around 58%) and have many potential applications. In this study, the drying of sago waste using a fluidized bed dryer (FBD), which offers more advantages than other drying methods, is analyzed via computational fluid dynamics (CFD) modeling. A two-dimensional (2D) FBD model is also developed and a mesh independency test is conducted immediately afterwards. A fine mesh is selected for the CFD model and a simulation is conducted using ANSYS Fluent 17.1 software (Ansys Inc., version 17.1, Canonsburg, PA, USA). The governing and discretized algebraic equations are solved by applying the phase-coupled semi-implicit method for pressure-linked equations. Both the Eulerian-Eulerian multiphase model approach and the turbulence model are applied in the simulation due to the turbulent flow in the dryer. A velocity of 1.30 m/s and temperature of 50 • C are selected as boundary conditions based on the optimum parameter values from previous experiments. The final moisture content that we aim to achieve is 10% or a moisture ratio of 0.25 in sago waste for the purpose of animal feed, so as to prevent bacterial growth and for packaging purposes based on common industrial practice. Both the drying rate and fluidization profile are examined at air velocities of 0.6, 1.0, 1.3, 1.8, and 2.2 m/s. Based on the results, the velocity range of 1.0 m/s to 2.2 m/s is deemed suitable for the fluidization and drying of sago waste with a particle size of 2000 µm for a drying simulation of 1 h. The drying rate is further examined at air temperatures of 50 • C, 60 • C, 70 • C, and 80 • C, whereas the fluidization profile is examined at particle sizes of 200, 500, 1000, and 2000 µm. The results reveal excellent fluidization at a particle size range of 500 µm to 2000 µm and a velocity of 1.3 m/s. Energies 2018, 11, 2383 2 of 13 9.2% hemicellulose, and 4% lignin [3] and have many potential functions, such as in the manufacturing of textile printing materials [4]. Several studies have investigated other usages of sago waste, including their adsorption of lead and copper [5] as well as their use in the production of bioethanol [6].Sago waste is usually mixed with wastewater and either discharged into streams or deposited in factory compounds. Each tone of extracted sago starch produces and dumps approximately one tone of sago waste into the nearby rivers. Data from the Malaysian Department of Statistics reveal that the country produced approximately 52,000 tons of sago starch in 2011. Nearly the same amount of sago waste was dumped in nearby rivers [7], thereby causing serious environmental problems such as water pollution. The high demand for biological oxygen (approximately 5820 mg/L) and chemical oxygen (approximately 10,220 mg/L) [1] in wastewater affects the marine life and water quality via microbiological degradation and by consuming the dissolved oxygen in the water. Som...

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Review of leaf drying: Mechanism and influencing parameters, drying methods, nutrient preservation, and mathematical models

Cited by 239 publications

References 87 publications

Experimental Investigations of Thin-layer Drying of Leaves in a Heat-Pump Assisted Tray-type Batch Drying Chamber

Experimental Investigations of Thin-layer Drying of Leaves in a Heat-Pump Assisted Tray-type Batch Drying Chamber

Replicating Arabidopsis Model Leaf Surfaces for Phyllosphere Microbiology

Simulation of a Fluidized Bed Dryer for the Drying of Sago Waste

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