Tray Dryer Research Articles

Thin-layer drying of cassava chips in multipurpose convective tray dryer: Energy and exergy analyses

Energy and exergy data of the drying of thin-layer cassava (Manihot esculenta) chips in a multipurpose convective-type tray dryer at 50 °C were collected to evaluate the technical performance of the drying system. The energy and exergy parameters, i.e. energy utilization, energy utilization ratio, energy efficiency, exergy inflow and outflow, exergy loss, and ex-ergetic efficiency were analyzed. The results indicate that the energy utilization, exergy inflow, exergy outflow, and exergy efficiency increased in the ranges of 9.53–24.66 kJ/s, 5.67–11.34 kJ/s, 2.21–8.04 kJ/s, and 38.90 %270.86 %, respectively, with increasing drying time. The results also show that the energy utilization ratio, energy efficiency, and exergetic improvement potential tend to decrease in the ranges of 0.49–0.68, 47.48 %–62.62 %, and 0.96–2.33 kJ/s, respectively, with increasing drying time. Additionally, stable exergy losses were observed during the drying process, within the range of 3.30–4.27 kJ/s during drying. Further research and development that could be used to improve the performance of this drying process are also suggested.

Effect of Drying Modes on Quality Characteristics of Dehydrated Green Leafy Vegetables

The present investigation was carried out for justifying the suitability of various dehydration techniques for desired quality of finished products. The commonly consumed green leafy vegetables viz. fenugreek leaves (Trigonella foenumgraecum) and spinach (Spinacia oleracea L.) were assessed for their commercial processing potential through dehydration technology. The selected fresh green leafy vegetables were washed and subjected to steam blanching. The pretreated vegetables were then dehydrated under different drying conditions i.e. sun, shade and tray drying to safe moisture level. The dried samples were evaluated for their dehydration process features, nutritional and sensory characteristics. The data on the dehydration technology revealed that tray dried green leafy vegetables found comparatively more wholesome, palatable and reported maximum retention of nutrients like vitamin C (35–47%), minerals (96%), with minimum drying time (2.30–3.30 hrs) and equilibrium moisture content (6%) as compared to rest of drying methods. The rate constant for drying of fenugreek and spinach leaves were found to be 0.0105 min−1 and 0.0088 min−1, respectively in tray drier. The tray drying method was found comparatively superior in retention of sensory quality parameters (color, texture and overall acceptability) over sun and at par with shade drying.

Foam-Mat Drying Characteristics of Custard Apple Pulp

In the present study, foam mat drying of the custard apple pulp have been conducted by using Glycerol monostearate (GMS) (0.5%, 1.5%, 2.5%, 3.5% and 4.5%) as foaming agent and 0.5% methyl cellulose (MC) as the stabilising agent with whipping time of 2, 4, 6, 8 and 10 minutes. Drying was carried out in a cabinet tray dryer at five different drying temperatures (50, 60 and 70 C) with foam thickness of 2, 4 and 6 mm. The optimum foaming conditions providing foam expansion of (61.11%), foam stability (94%) and lowest foam density (0.60 gm/cm3) was found to be 3.5% GMS with 0.5% methyl cellulose whipped for 6 minutes. The tray drying of foamed pulp took 240-450 minutes whereas the non-foamed pulp took 420 to 450 minutes saving about 180-240 minutes drying time. Among all the parameters studied, the combination of 3.5% GMS and 0.5% methyl cellulose whipped for 6 min dried at 60 C with foam thickness of 4 mm was found to be the best treatment for custard apple powder preparation.

Empirical Drying Model for the Mass Transfer and Drying Kinetics of Treated and Untreated Saba Banana Slices

Banana fruit is a delight in most Nigerian homes, which is usually eaten fresh, but recently, dried bananas have found their way into the daily snacks. Unfortunately, this precious fruit suffers a huge post-harvest loss due to its high moisture content. This work includes the fitting of the drying process to empirical models to predict the drying process using a locally fabricated convective tray dryer. To prevent discolouring during drying, samples were treated with a 1:4 lemon juice. Drying was carried out (for both treated and untreated samples) at temperatures of 40 0C, 50 0C, 60 0C, and 70 0C. Four empirical models were examined (Newton, Peleg, Henderson-Pabis, and Logarithmic models), and the model with the highest R2 and least RMSE values was adopted as the best fit for each drying temperature. Results showed that the Peleg model favoured air-drying and at temperatures of 50 0C and 600C for untreated and treated samples, respectively, while other models considered, best described the drying at other temperatures, for both treated and untreated samples.

Development of a Microcontroller Based Tray Dryer Machine

Development of a Microcontroller Based Tray Dryer Machine

A Comparison of Drying Performances of Red and Green Apple Particles in a Tray Dryer

The green and the red apples were selected as drying materials in order to dry in a tray dryer for this study. They were washed with distilled water to wipe out all contaminants that can be affected negatively the results of experiment and they were chopped to the same dimensions. The length, width and thickness of each apple piece were adjusted as 65 mm, 37 mm and 12 mm, respectively. The apple particles were weighed with precision scales and they were grouped into 50 g, 100 g and 200 g. Then the particles were placed in the tray dryer for each set of experiments. Thereafter, drying process was carried out at different weights of red and green apple particles (mp), drying air velocity (U) and drying temperatures (Td). Herein, the moisture content (MC) is considered as the significant parameter in order to express the drying performance of drying materials. Moreover, energetic efficiency and normalized moisture content are compared with the empiric equation, which is proposed for the drying systems. The experimental study is performed with the range of 50 g ≤ mp ≤ 200 g, 18 % ≤ MC ≤ 614.29 %, 0.03 ≤ MR ≤ 1, 59 oC ≤ Td ≤ 99 oC and 0.992 m/s ≤ U ≤ 1.488 m/s. The result of this study is that the red apple particles have better drying performance at same conditions due to its physical properties when compared to green apple particles

Mathematical Modelling and Tray Drying Kinetics of Loquat Eriobotrya japonica

The present study was aimed to investigate drying of loquat slices in tray dryer at different temperatures Drying was conducted at 45°C, 55 °C, and 65°C at constant air velocity of 0.5 m/s in tray dryer;time taken for drying of slices was 12 h, 10 h and 9h respectively. The analysed moisture data was fitted in four different drying mathematical models, i.e. Henderson and Pabis, Page, Logarithmic and Newton (Lewis).Statistical analysis predicted that Page model was best-fitted model for describing drying characteristics of loquat slices. Best-fitted model was selected by obtaining maximum value of regression coefficient (R2 ) and minimum value of chi square (χ2) and root mean square error (RSME). It was observed that shrinkage percentage was less at higher temperature as compared to the lower temperature, i.e., 45°C.

The chemical composition of the fruit of Pyrus L. genus representatives

Aim. The article aimed at determining the content of the basic elements of the chemical composition (total contentof water, titrated acids and mass fraction of dry soluble substances) in the fruits of Pyrus L. genus representatives and the acidity of their cell sap (pH). Methods. The analyzed fruits had been gathered from plants of the species and pear cultivars collections growing in the National Dendrological Park “Sofiyivka” of NAS of Ukraine and Uman National University of Horticulture (P. communis L., P. pyrifolia (Burman f.) Nakai and ‘Glek’, ‘Kniahynia Olga’ and ‘Clapp’s Favorite’), as well as at M. M. Gryshko National Botanical Garden of NAS of Ukraine (P. betulifolia Bunge, P. calle-riana Decne, P. elaegrifolia Pall., P. pashia Buch.-Ham. ex D. Don., P. georgica Kuth.). The chemical composition of the fruits had been determined by conventional methods using pH tester (pH-150M), a refractometer (URL-1), and an atmospheric tray dryer (SUP-4). The level of titrated acids (in terms of malic acid) had been defined by the volume titration method according to DSTU EN12147–2003. Results. The pH in the studied Pyrus fruits varied from 3.2 to 4.8, indicating the acidic response of the cell sap of the fruits of the studied species and cultivars of pear. The water content of pear cultivars (85.83–90.0%) was higher than in Pyrus species (67.36–79.56%) except for P. pyrifolia (87.1%). In most of the studied Pyrus representatives (‘Glek’, P. betulifolia, P. calleriana, P. communis, P. pashia, P. georgica, P. elaegrifolia), the titrated acid index ranged from 0.18 to 0.25%. The lowest rates were in P. pyrifolia (0.11%) and ‘Kniahynia Olga’ (0.09%), and the highest ones were in the ‘Clapp’s Favorite’ (0.31%). The more soluble solids had been found in P. betulifolia, P. georgica, P. elaegrifolia, P. pashia, and P. calleriana (14.6–16.1%), whereas in the other species and cultivars their content did not exceed 8.2–12.4%. Conclusions. Thus, according to the complex of indicators, the fruits of species and cultivars of the genus Pyrus contained 67.36–90.00% of water, 8.2–16.1% of soluble solids, 0.09–0.31% of titrated acids, in the acidic cell sap reaction with pH was of 3.21 to 4.80. Based on the data obtained, the cultivars of ‘Clapp’s Favorite’ and ‘Kniahynia Olga’ can be used for fresh consumption, ‘Glek’—for drying, and P. pyrifolia — for involvement in the breeding programmes.

Physical properties of yellow passion fruit seeds (Passiflora edulis) during the drying process

The reuse potential of passion fruit seeds to obtain functional ingredients can find many industrial applications. This requires knowledge of their physical properties for the design of conveyors and equipment. The objective of this study was to determine the physical properties of passion fruit seeds during drying and to evaluate the feasibility of using digital images to determine the dimensional properties of seeds in comparison to caliper. Passion fruit seeds with initial moisture content, in dry basis (d.b.), of 0.402 (decimal) were subjected to drying in a cylindrical tray dryer at 45 ± 2 °C to different moisture content levels and were characterized by their physical properties. Unit specific mass, mass of one thousand seeds, and seed size and shape were evaluated. The characteristic dimensions of the seeds were obtained by caliper and digital image processing. The digital image processing method was satisfactory to obtain the characteristic dimensions of passion fruit seeds. The dimensional properties did not show significant difference (P ≤ 0.05) during the drying process, indicating low contraction of the characteristic seed dimensions. The seeds presented volumetric contraction of approximately 4 %, which was represented by the Bala & Woods adapted model. The mass of one thousand seeds showed a reduction of approximately 21 % with the decrease of moisture content. The unit specific mass ranged from 1121 to 1022 kg m-3 for moisture contents of 0.402 and 0.047 (decimal, d.b.), respectively. These results indicate that the separation of passion fruit seeds as a function of moisture content should be performed by densimetric methods.

Effect of oven and intermittent airflow assisted tray drying methods on nutritional parameters of few leafy and non-leafy vegetables of North-East India

Given a sizable proportion of bio-resource production in the North-east (NE) India and the need to enhance the shelf life of perishable horticultural regional produce, this work addresses the optimality of inexpensive oven and intermittent airflow assisted tray drying processes for Kolmou (Ipomoea aquatica Forssk.), Pui (Basella alba), Jatialao sak (Lagenaria siceraria leaves), Kolphul (Musa balbisiana Colla blossom), Kaskal (Musa splendida), green Komora (Benincasa hispida) and Posola (Musa balbisiana Colla pseudostem) vegetables of NE India. Characterization parameters for process parametric optimality include proximate analysis based evaluation of moisture content, yield, carbohydrate, crude protein, soluble protein, vitamin C, antioxidant activity, ash, crude fibre and fat content. For most vegetables, tray drying process performance is superior in terms of better moisture removal, higher yield and higher anti-oxidant activity. Among all considered samples, tray dried Kolmou possessed highest antioxidant activity. Vitamin C content was seen to be highest in tray dried Komora.

The characteristics of “indigenous yeast mold” dried culture using tray dryer

This research studied the effect of temperature and drying time in making “Indigenous Yeast Mold” dried culture using tray drier. There are 2 dried culture, names AC and CC. AC consists of 3 mold and 1 yeast strains, while CC consists of 7 mold and 3 yeast strains. The temperature of drying used were 40°C and 50°C and the drying time were 0, 1.5, 3, 4.5, and 6 hours. The results showed that the quality of dried cultures AC and CC were influenced by the drying times and temperatures. The water content, viability of microorganisms, Aw, and pH value decreased with the increasing of drying time and temperature. The drying time at the temperature of 40°C affected the water content and water activity of AC and CC dried culture significantly. While the drying time at the temperature of 50°C affected the moisture content, water activity, viability of microorganisms, and pH value of AC and CC dried culture significantly. The desired water content in dried culture is 10% (wb) or 11.1 (db). To reach the water content of 10%, at the drying temperature of 40 °C, the AC dried culture required 4.46 hours, while CC required 4.44 hours. Meanwhile, at the drying temperature of 50 °C, the AC dried culture took 3.46 hours, while CC required 3.33 hours. Drying could be done at 50 °C without changing the quality of the dried culture.

Effect of cultivars, pretreatment and drying on physicochemical properties of Amla (Emblica officinalis) gratings.

Effect of four different cultivars and salt pretreatment on drying of Amla (Emblica officinalis) gratings were studied. Quality attributes namely, ascorbic acid, total phenolic content, antioxidant activity and colour were evaluated for dried (using Cabinet tray dryer at 55 ± 2°C for 8h) and stored (refrigerated, ambient and accelerated condition) samples of four cultivars (Krishna, Kanchan, NA-7 and Chakaiya). Salt pretreated dried samples showed better retention of nutrients and colour as compared to untreated. Retention of ascorbic acid, total phenolic content and antioxidant activity (IC50 value) in pretreated dried samples were in the range of 79.51-84.89%, 176.5-220.3mg GAE/g db and 9.48 to 17.74mg/µl, respectively. Colour retention was also found to be better in salt pretreated samples. Ambient storage condition resulted in higher retention of ascorbic acid and colour compared to accelerated condition. Taking into consideration, the nutritional value of the fresh Amla, ability to retain nutritional value and color during drying and storage, NA-7 cultivar Amla (pretreated with 1% salt, tray dried at 55°C for 8h) is the most suitable for preparation of Amla powder. The method developed in the present work is devoid of blanching step and found to be effective in retaining the nutrients during drying and storage and can be employed also for drying of similar fruits and vegetables.

The drying rate of mushroom on tray dryer and effect of mushroom powder on organoleptic properties of Batagor

Oyster mushrooms and straw mushrooms are currently great demand in the food industry. Mushrooms have the characteristics that are easily damaged and decomposed. The effort of preserving mushrooms is by drying using hot air at a certain temperature and flow rate. The purpose of this study was to determine the drying rate of oyster mushrooms and straw mushroom in variations temperature and flow rate of hot air. In this study, the drying of mushrooms was carried out with a tray dryer that has a stacking rack with dimensions of 30 cm x 25 cm. The temperature variations used were 30, 40, 50ºC and the dryer air flow rate was 1, 2, 3 m/s. The dried mushroom with a moisture content of less than 10% is mashed to a powder then added to the food (Batagor) for an organoleptic test. The best drying result is obtained at temperature 50°C and flow rate of 3 m/s with a drying rate of 1.52 kg water/m2.h. Organoleptic test on Batagor produces the most preferred flavour by using type mushroom of Volvariella volvacea, and for aroma and texture preferably with Pleurotus ostreatus.

Numerical Simulation of air Temperature and air flow Distribution in a Cabinet tray Dryer

The quality of dried product can be enhanced in cabinet tray dryers through a uniform distribution of drying air flow and temperature. In this work, a numerical investigation is conducted to examine the consequence of air movement on the quality of product dried in a convective tray dryer. The temperature and velocity contours of air in the drying chamber are numerically determined for three different geometries of cabinet tray dryer and are compared. A good harmony is found between the predicted data from CFD and experimental data from the literature. This work will enable us to optimize the drying chamber design for uniform dispersal of air flow and temperature and to improve quality of dried product for large scale applications.

Experimental Evaluation of a Diesel Cogeneration System for Producing Power and Drying Aromatic Herbs

The focus of this work was to evaluate the thermal performance of a cogeneration system used to produce power and dry aromatic herbs. The waste heat from the exhaust gases of the diesel engine was recovered to heat air using a thermosyphon heat exchanger. The heated air was employed in a convective tray dryer in order to dry Origanum vulgare, Mentha spicata, and Ocimum basilicum. The experiments were carried out at full load in a stationary compression ignition engine coupled to a generator. The maximum global energy efficiency of the cogeneration system was 40.14%, and the effectiveness of the heat exchanger achieved 39%.

Production of natural colorant powder from Clitoria ternatea l. using tray dryer which is dehumidified by zeolite

One of food additives that are usually added to food is coloring agents. The use of synthetic colorant in food products often causes health problems. Telang flowers, or Clitoria ternatea L., have blue color that indicates the presence of anthocyanins. Anthocyanin is a flavonoid compound that has positive health benefits. Referring to this, the flowers can potentially become natural coloring agents. This research aims to examine the effect of pH on anthocyanins, the effect of maltodextrin concentration and temperature on water content. So that the best conditions are obtained for the drying process and obtained powder that has anthocyanin content with low water content. The research was conducted in several stages, namely extraction, drying and analysis of results. The extract is varied in its pH to obtain pH with highest anthocyanin. Drying was carried out with variations in maltodextrin concentrations of 0 and 8%, and temperatures of 40, 60 and 80°C. Water content analysis for 120 minutes every 10 minutes. The results showed that at pH 2, the highest total anthocyanin was obtained. The higher the drying temperature and maltodextrin concentration that is added, the time needed to dry the extract will be faster. Lower moisture content is produced with higher maltodextrin concentration and temperature.

The study explores the effect of onion (allium cepa l.) drying using hot air dehumidified by activated carbon, silica gel and zeolite

Dehumidified air can be used to reduce the drying time. A batch-type tray dryer with hot air dehumidified by three different desiccants (i.e. activated carbon, silica gel and zeolite) were carried out to determine the optimum drying time. This study concerns the comparison of the between those desiccants. One mm sliced onion were dried at controlled temperature (40°C, 50°C, 60°C and 70°C). The weight of the samples were measured every 10 minutes for two hours. Results indicate that hot air dehumidified by zeolite gives the shortest drying time compared to the activated carbon and silica gel. Page and modified Page models are the most suitable model to experiment with the value of R2 (0.8971 – 0.9588). The highest k value (0.6132934) is achieved through the treatment at temperature 70°C using zeolite.

Kinetics of Moisture Loss during Dehydration of Drum Stick Leaves (Moringa Oliefera) In a Bio-Mass Tray Dryer

Studies were conducted on a newly developed bio-mass dryer installed with wire mesh tray with natural convection. Drum stick leaves were dehydrated using agri-waste as fuel for the dryer. Agriculture fields generate lot of waste in the form of fodder, leaves, sticks and roots, etc, It has been a major problem of pollution when farmers put these waste materials on to fire. The dryer is made of bricks to suit the drying temperatures of foods. Dryer is designed to generate temperature of the order of 50 – 100 deg C to suit the heat requirements of most of the vegetables, especially for green leafy vegetables. This paper reports the data collected during the dehydration of drum stick leaves and data analyses on kinetics of moisture changes. Nutritional values are measured and reported. Data of moisture loss is modeled using exponential and polynomial equations. The highest R square values are obtained with polynomial kinetic model. The moisture rate is maintained below the standard value in all the experimentation.

Influence of hot-air drying and freeze-drying on functional, rheological, structural and dielectric properties of green banana flour and dispersions

The green banana flour (GBF) is a rich source of resistant starch, minerals, and phytochemicals and can be used as a functional ingredient for food product development. Two types of drying, namely, freeze-drying (FD) and hot-air tray drying (TD) were employed for the production of GBF, and thereafter, the resultant flour quality was compared by measuring physicochemical, functional, structural, dielectric and rheological properties. The structural and rheological properties of flour samples were examined by using scanning electron microscopy, X-Ray Diffractometer, rheometer, and visco-amylograph. Both the TD and the FD affect the particle size, color, starch, resistant starch, and water hydration properties of GBF significantly. During thermal scanning, the peak gelatinization temperature (Tp) (82.5–83.4 °C) and the starch-lipid melting transitions (102.4–109.2 °C) were detected in both samples. The flour in dispersion (F/W = 1:3) showed the solid-like behavior (G′>G″) and the mechanical rigidity influenced by the drying methods (P < 0.05). The dielectric properties of the two types of dried flour dispersions varied with the process temperature, in particular, above the gelatinization temperature. The drying methods did not influence the crystallinity of the starch. The information obtained in this study would help processors to consider the GBF as an important ingredient in food product development by selecting a suitable drying method.

Antioxidant properties and selected phenolic acids of five different tray-dried and freeze-dried mushrooms using methanol and hot water extraction

Mushrooms are health foods due to their nutritional values and antioxidant properties. This study investigated chemical properties, total phenolic content (TPC), antioxidant activities (2, 2-diphenyl-1-picrylhydrazyl; DPPH and 2, 2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid); ABTS) and selected phenolic acids from five different tray-dried and freeze-dried mushrooms (Pleurotus ostreatus, Pleurotus pulmonarius, Schizophyllum commune, Volvariella volvacea and Lentinus edodes). The extracts were prepared using methanol and hot water extractions. The results revealed that V. volvacea had the highest protein (28.70%) and ash (9.48%) contents. There were significant differences among some tray dried and freeze dried mushrooms regarding TPC, DPPH and ABTS. However, tray drying tended to improve TPC, DPPH and ABTS in P. ostreatus, P. pulmonarius and L. edodes. Among five mushroom species, both methanol and hot water extractions of V. volvacea had the highest TPC, DPPH and ABTS values but there were no significant differences between mushrooms prepared using tray drying and freeze drying. Moreover, the yield and contents of gallic acid and p-hydroxybenzoic acid from the hot water extracts were higher than from the methanol extracts. Therefore, tray-dried V. volvacea had the most potential as a natural antioxidant and could be used as a functional ingredient in healthy food products.