An experimental study on drying characteristics and kinetics of fi gs (Ficus carica (original) (raw)
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Journal of food Engineering, 2004
In order to establish the influence of the drying air characteristics on the drying performance of figs (ficus carica) several drying tests have been carried out in a laboratory scale tunnel-dryer. The dryer using ambient heated air and working in closed loop was equipped with a continuous monitoring system. The investigation of the drying characteristics has been conducted in the temperature range of 55–85 °C and the airflow in the range of 0.5–3 m/s. An Arrhenius-type equation was used to interpret the influence of the drying air parameters on the effective diffusivity, calculated with the method of slopes in terms of energy of activation, and this was found to be insensitive to air velocity values higher than 2 m/s. The effect of the air temperature and velocity on the drying constants was determined by fitting the experimental data using regression analysis techniques. The influence of the air temperature on the drying kinetics of figs has been shown to follow the Arrhenius relationship. The strong influence of air temperature and velocity at the early stages of drying was evident, as well as the relative insensitivity of the drying process at the later stages. A value beyond which the increase of the airflow velocity has no significant effect on the drying rate was encountered and was determined to be 2 m/s, indicating the predominance of the internal mass transfer resistance over the external one. The investigation revealed that the drying kinetics is most significantly affected by temperature, with the airflow velocity having a limited influence on the drying process. Correlations expressing the drying constants and effective moisture diffusivity dependence on the drying-air parameters are reported.
MATHEMATICAL MODELING FOR DRYING FIGS IN THIN LAYER USING MECHANICAL DRYER
In the present work, selected mathematical thin-layer drying models were fitted to experimental data using non-linear regression analysis techniques. The drying behavior was examined and simulated using four different thin layer drying models (simple, modified simple, logarithmic and two-term exponential model). An empirical equations relating the studied drying parameters with the drying constants of each model were also developed. The analysis was conducted based on the final moisture content (Mf) and the equilibrium moisture content (Me) for calculating the moisture ratio (MR). The results indicated that, both forms of different drying models equations described the drying behavior of whole figs satisfactorily as indicated by the high values of coefficient of determination (R 2 ) and low values of standard error (SE).
Applicability of a single-layer drying model to predict the drying rate of whole figs
Journal of food engineering 81 (3), 553-559, 2007
In this study the mathematical modelling of single-layer drying of whole (uncut) figs (Ficus carica L. var. tsapela) in an experimental heat pump of closed cycle, is presented. A range of drying air velocities (1.0-5.0 m/s) and temperatures (46.1-60°C) were tested in drying whole (uncut) figs to moisture content below 30% w.b. Drying temperatures higher than 50°C, were lay beyond the operational limits of the specific heat pump and therefore a set of auxiliary electric resistances were used. Seven thin-layer drying models were fitted to drying experimental data of figs, implementing non-linear regression analysis techniques. The statistical analysis concluded that the best model in terms of fitting performance was the Logarithmic one. Correlations between the model parameters and the drying conditions to calculate moisture ratio MR in relation to the drying time, were determined and reported.
Scientific Reports, 2021
First convectional thin layer drying of two fig (Ficus carica L.) varieties growing in Morocco, using partially indirect convective dryer, was performed. The experimental design combined three air temperature levels (60, 70 and 80 °C) and two air-flow rates (150 and 300 m3/h). Fig drying curve was defined as a third-order polynomial equation linking the sample moisture content to the effective moisture diffusivity. The average activation energy ranged between 4699.41 and 7502.37 kJ/kg. It raised proportionally with the air flow velocity, and the same patterns were observed for effective moisture diffusivity regarding drying time and velocity. High levels of temperature (80 °C) and velocity (300 m3/h) lead to shorten drying time (200 min) and improve the slices physical quality. Among the nine tested models, Modified Handerson and Pabis exhibited the highest correlation coefficient value with the lowest chi-square for both varieties, and then give the best prediction performance. Ene...
Thin-layer drying rates of fig fruits were determined experimentally under different conditions of the drying air temperature, relative humidity and velocity, and under different initial moisture content of the fruits. Twenty-four drying tests were run by an experimental dryer, locally designed and fabricated for thin-layer drying. The results showed that the drying air temperature, the fig fruits initial and final moisture content had the greatest effect on the drying rate of fig fruits, followed by the drying air relative humidity. Air velocity had the least effect. The objectives of this research work could be summarized as: expressing the loss of moisture during the drying process of the fruit or the vegetable, as a function of the affecting factors of the drying process, the determination of the fruit or the vegetable drying rate as a function of all the affecting factors, the determination of the needed time through each stage of the drying process, and how to benefit from the findings of this research work in conducting productive drying operation of fruits on large scale. This work was planned for mathematically expressing the loss in fig fruits moisture throughout the drying process as a function of the affecting factors using multiple linear regression analysis. The derived mathematical expressions which relate the results of the drying process with the affecting factors could be used in the determination of the instantaneous moisture content of the fruits at successive time intervals. These equations are especially useful for solar drying under which the drying air properties are under continuous changes along the time of the day and along the days of the year. The derived mathematical equations covered all the stages of the drying process, i.e, the stage of the primary increasing drying rate, the stage of the constant drying rate and the stage of the falling drying rate.
DRYING FIGS USING DEVELOPMENT MECHANICAL DRYER
The present work was conducted to study and simulate the drying behavior of whole figs fruits under different drying parameters. The approach led to develop a small scale industrial figs dryer using butane-gas as heat energy source and also describe the change in whole figs moisture content during actual drying process using the proposed dryer. The experimental were carried out using fresh whole figs "Ficus Carica" its local name is "Sultani". Whole figs fruits were treated before drying by treatment (A): the fruits sulfured by dipped in 1. 5% aqueous sodium metabisulfit and, treatment (B): the fruits were dipped in 1% sodium hydroxide before treated with solution of 1.5% sodium metabisulfit. Four levels of drying air temperature (55, 65, 75 and 85 °C) and four levels drying air velocity (0.2, 0.4, 0.6 and 1 m/s) The dryer has been developed and tested for drying whole figs fruits at Agriculture Engineering Department, Faculty of Agriculture, Kaferelsheikh University. The results showed that, the reduction rate of whole figs moisture content was increased with the increasing of drying air temperature and air velocity in all pretreatment of simple whole figs. On the other hand, the whole figs moisture content reduction rates on the treatment (B) were higher than that in treatment (A) for all the combination of the parameters. The recorded drying time for drying whole figs from an initial moisture content of about 223-400% d.b to a final moisture content of about 18-20 % d.b were 35-20 hours under different drying parameters. Heating control unit using butane-gas was used to control heat source in drying air temperature with fluctuation of about ±1.7 °C for all levels of drying air temperature. The total capacity of the dryer is about 40 kg of fresh figs producing about 10 kg of dried figs, the calculated operation cost of the dryer approaches about 6.3 LE/kg of dried whole figs fruits. The developed dryer of whole figs fruits showed good mechanical and thermal performance. Stamatios, et al., (2005) studied the drying air characteristics on the drying performance of figs (Ficus Carica) several drying tests have been carried out in a laboratory scale tunnel-dryer. The investigation of the drying characteristics has been conducted in the temperature range of (55 -85 o C) and the air velocity in the range of (0.5 -3 m/s). An Arrhenius-type equation was used to interpret the influence of the drying air parameters on the effective diffusivity, calculated with the method of slopes in terms of energy of activation, and this was found to be insensitive to air velocity values higher than 2 m/s. , mentioned that, application of combined electromagnetic radiation and hot air is gaining momentum in food processing. A combined infrared and hot air heating system was developed for drying of vegetables. A conveyors drying system having three chambers was fitted with mid-infrared (MIR) heaters for radiative heating. Through-flow hot air circulation was also provided for convective mode heating. The system was designed to operate under infrared, hot air and combination mode independently. The performance evaluation studies indicated that combination drying of carrot and potato at 80 o C with air at a velocity of 1 m/s and temperature of 40 o C reduced the drying time by 48%, besides consuming less energy (63%) compared to hot air heating. Combination drying also gave better results over infrared heating alone. The energy utilization efficiency of the dryer was estimated to be 38% for both carrot and potato drying.
Drying of ground and half-cut figs (Ficus carica L., var. Mission) was investigated at three temperatures (45, 55, and 65 ∘ C). Their effective moisture diffusivity ( eff ) was estimated by using the slope method. eff values for ground figs were 5.15 × 10 −10 , 9.96 × 10 −10 , 1.07 × 10 −9 m 2 s −1 and for half cut figs 5.88 × 10 −10 , 1.66 × 10 −9 , and 2.08 × 10 −9 m 2 s −1 at 45, 55, and 65 ∘ C, respectively. Dehydrating fig samples showed a similar behavior: higher eff values at higher temperatures and activation energy (E ) values in the range of other foodstuffs. Half-cut figs needed about twice more energy and time than ground figs to carry out the dehydration; E values were 56.86 and 28.21 kJ mol −1 , respectively. The drying process increased the total phenolic content and degraded the anthocyanin content of figs; however, it enhanced the dried figs antioxidant activity. Dehydrating ground figs was faster and maintained its functional properties better than half-cut figs.
Thin-layer drying rates of fig fruits were determined experimentally under different conditions of the drying air temperature, relative humidity and velocity, and under different initial moisture content of the fruits. Twenty-four drying tests were run by an experimental dryer, locally designed and fabricated for thin-layer drying. The results showed that the drying air temperature, the fig fruits initial and final moisture content had the greatest effect on the drying rate of fig fruits, followed by the drying air relative humidity. Air velocity had the least effect.
2003
An experimental dryer was locally designed and fabricated in the Agricultural Engineering Department, Faculty of Agriculture, Cairo University for the determination of the impact of the affecting factors on the drying time of fruits due to the continuous variation in drying conditions along the drying period, the continuous changes in the moisture content of the drying fruit and vegetable and hence, the continuous variation in the drying rate during the whole drying process. All these facts make it difficult to determine the volume of air needed for any drying process, the energy requirement for the process, the time duration of the process, and the most suitable values for the affecting factors to accomplish a successful drying process. It was found that it is better to design a special apparatus and utilizing it as a thin layer dryer, in which all the affecting factors can be controlled to give all the variations expected in solar dryers. The experimental drying system employed a blower to force the drying air through a heating unit and then through the drying tray. The experimental apparatus was equipped with an electric balance for continuous recording of the drying tray weight with its fruit content throughout the whole period of drying. This dryer was tested for a period of 24 hours to assure the success of the control of the temperature, relative humidity, velocity of the drying air. After that, the dryer was used for determination of a thin-layer drying rates of fig fruits experimentally under different conditions of the drying air temperature, relative humidity, velocity and initial and final moisture contents of the fruits. The results show the high reliability of the results obtained from the utilization of the designed apparatus when conducting different drying experiments on fig fruits. The results also show that the drying air temperature, the fig fruits initial and final moisture content had the greatest effect on the drying rate of fig fruits followed by the drying air relative humidity. Air velocity had the least effect.
Effect of drying under plastic tunnels on drying rate and quality of fig (Ficus caricaL. ‘Sarılop’)
Acta Horticulturae, 2017
Commercial sun-drying is widely practiced in fig (Ficus carica L. 'Sarılop') production in western Turkey. The quality can be adversely affected by the climatic conditions due to dew formation and risk of early rains. The study aimed to test a plastic tunnel developed as a model for fig drying and compare with open air conditions. Fruit partially dried on the tree were collected and further dried on trays placed in open-air or under tunnels. The trial was performed twice in August (Trial 1: early season) and in September (Trial 2: as late season). The temperature and relative humidity were monitored in both environments. The samples were taken at 0, 24, 48, 72, 96 and 120 h after placed on drying trays to analyze moisture content (%), water activity (a w) and physical and chemical quality parameters. The drying was terminated when moisture content was ≤22 and/or water activity ≤0.65. In Trial 1, the fruit moisture content and a w levels achieved after 72 h under the plastic tunnel were 22.3% and 0.63, respectively. However, these values were obtained after 96 h in open air. In Trial 2, similar levels were reached after 96 and 120 h under plastic tunnel and open air, respectively. The plastic tunnels shortened the drying period for 24 h in the early and late season.