Farhad Salmanizade; Ali Asghar Zomorodian; Hossein Rahmanian; Hassan Safiyari
Abstract
Introduction: Persimmon fruits are subjected to different environmental conditions from harvest to consumption. Foods, those are exhibiting characteristics of both liquid and solid, are described as viscoelastic where stress relaxation and strength properties are time dependant. Knowledge of viscoelastic ...
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Introduction: Persimmon fruits are subjected to different environmental conditions from harvest to consumption. Foods, those are exhibiting characteristics of both liquid and solid, are described as viscoelastic where stress relaxation and strength properties are time dependant. Knowledge of viscoelastic properties of foods and agricultural materials are important when considering harvesting, handling, transportation, processing, and storage. Also the data on viscoelastic properties are required as an input for mathematical models, which describe and predict internal stress and cracking during different handling and processing procedures. The mechanical properties are considered one of the most important four parameters, which reflect the quality of food material. Those parameters include texture, firmness and chewability. Viscoelastic material exhibit stress relaxation phenomena, which is one of the most important factors in characterizing agricultural materials. The objectives of the current study were: (1) to obtain data to describe the stress relaxation characteristic of Persimmon fruits during Storage, (2) to investigate the effect of storage time on stress relaxation properties, and (3) to find the best model to describe the obtained stress relaxation data.Materials and Methods: The persimmon fruits were manually picked up at maturity stage from persimmon trees in a garden, in Fars province, Iran. They were handled to Biophysics laboratory in Agricultural Engineering department, at Shiraz University, on the foam sheets in one layer array for minimizing any likely compaction. Initial moisture content was determined by gravimetric method in an oven at 70C till obtaining constant successive weight loss of 0.001 g. The initial moisture content was 44.26% (d.b). Since the rheological characteristics of fruits are important for any processing operation, viscoelastic behavior of persimmon fruits during storage in environmental conditions was investigated using estimating its relaxation parameters from experimental stress relaxation data. The rheological behavior of persimmon fruits was evaluated to uniaxial compression test for relaxing the stress during 480 s. Texture Profile Analyser (TPA) (TA.XT2 plus model, Stable Microsystems, England) with Exponent Lite (Version 4,0,8,0, UK) software was used to compress whole date samples and export data into Excel worksheets. TPA was equipped with a 30 kgf load cell. The cross head speed was adjusted on 1 mm/s, and samples compressed with 30% strain. The cross head then kept at 30% of strain for relaxing the stress in 480 s duration. A chamber with temperature control circuit was fabricated around the TPA cross head to prepare constant temperature identical to sample temperature with an accuracy of ±0.1C during the stress relaxation tests. All tests were performed with ten replications. Three popular stress relaxation models, namely the generalized Maxwell with three elements, Nussinovitch, and Peleg were fitted to experimental data and was used from R-square, standard error of estimation (SEE) and percent of average relative error (ARE%) indexes for evalution of models.Results and Discussion:The force–time curves were converted to stress–time curves by dividing the true compression force values to the corresponding true values of contact surface area. Analysis of variance showed that storage time had significant effect on initial stress relaxation. The results showed that the magnitude of initial stress (stress at time zero) required to create a fixed strain on whole fruit was significantly decreased up to 80% during storage in environmental conditions, but the relaxation time was increased at the range of 312.10 to 353.90 s. Based on the results, elastic behavior of persimmon fruit was enhanced and its firmness decreased during fruit storage. Persimmon is sugar rich fruit that its behavior is principally partly controlled by physico-chemical properties of sugar. Changes in sugar type as a result of enzymatic action are taken place during the storage process. However, in the present study all samples were in the time of maturation, and therefore the physical state of sugar was influenced by free water which is resulted in increasing in fruit moisture content. Stress relaxation curves were plotted at different storage time. Some variations were apparently observed among the curves. Sucrose decreased initial stress decay rate and increased proportion of un-relaxed force. Variations in stress decay rate might refer to the amount of initial stress which was affected by physic-chemical properties of the sugar. Recall that nonlinear regression method with non-negative constraint was used to derive the models constant.Conclusion: All three models were valid for quantifying the viscoelastic behavior of persimmons; however the generalized Maxwell with three elements (with R2=0.999, SEE=0.017 and ARE=0.19%) and Nussinovitch (with R2=0.996, SEE=0.057, ARE=0.36%) were the best models in predicting experimental data.
Hamed Darabi; Ali Asghar Zomorodian
Abstract
Lemon is one of the most important citrus fruit and is consumed as fresh and dry. In this study the effect of
fruit moisture content on the size, sphericity, geometric mean diameters and kernel density were studied. The
bulk density and porosity were also evaluated in three different arrangements. ...
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Lemon is one of the most important citrus fruit and is consumed as fresh and dry. In this study the effect of
fruit moisture content on the size, sphericity, geometric mean diameters and kernel density were studied. The
bulk density and porosity were also evaluated in three different arrangements. Airflow resistance is a
fundamental parameter for designing an efficient drying and aeration systems for lemon fruit bed. Using a
laboratory test rig, two sets of experiments were carried out: thick and thin layers. In the thick layer experiments
4 bed depths, 11 air flow rates and 4 air temperatures were adopted as independent variables. In the thin layer the
effect of filling arrangements in three patterns: A, B and random, at 5 moisture contents and 11 flow rates on
pressure drop were envisaged. Results showed that all the physical parameters listed decreased by reducing
moisture content. Results indicated that resistance to airflow through a column of lemon fruit increased with
increasing bed depth and airflow rate. In the latter experiment pressure drop decreased with a decrease in
moisture content. Airflow rate was the most significant factor affecting the pressure drop of lemon fruit in the
both experiment. Also the filling arrangement B has a higher affect on pressure drop comparing with other
arrangements. Three applicable models (Shedd, Hukill & Ives, and Ergun) were used to evaluate the pressure
drop data. The Ergun model, with higher values for coefficient of determination and lower values for root mean
square error, is the best model for predicting pressure drop across lemon fruit bed for the conditions studied.
Hassan Safiyari; Ali Asghar Zomorodian; Hossein Rahmanian; Farhad Salmanizade
Abstract
Physical properties are often required for designing post harvest handling and processing equipment for agricultural products. Persimmon (khormandy cultivar) is rich in vitamin A, calcium, potassium, tannic acid and antioxidant phenolic compounds. In this study changes in the physical properties of persimmon ...
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Physical properties are often required for designing post harvest handling and processing equipment for agricultural products. Persimmon (khormandy cultivar) is rich in vitamin A, calcium, potassium, tannic acid and antioxidant phenolic compounds. In this study changes in the physical properties of persimmon fruit during storage were studied. Properties such as fruit dimensions, mass, geometric mean diameter, arithmetic mean diameter, equivalent diameter, sphericity, aspect ratio, surface area, volume and the static coefficient of friction on three surfaces (plywood, glass, and the galvanized iron sheet) were investigated. The results showed that the mean values of all physical properties decreased with increasing storage time. Experiments were carried out at initial moisture content of 44.26% d.b. Dimensions decreased from 56.01 to 52.57 mm in length, 54.19 to 50.01 mm in width, and 36.72 to 32.48 mm in thickness during storage time. Arithmetic mean diameter, geometric mean diameter and equivalent diameter varied from 48.07 to 44.06 mm, 48.95 to 45.06 mm, and 48.7 to 44.75 mm, respectively. The results also revealed that with increasing in storage time, the sphericity, the aspect ratio and the surface area of persimmon fruits were decreased from 0.859 to 0.8383, 0.6548 to 0.6211 and 72.99 to 61.41 mm2, respectively, while average volume and mass ranged from 59.18 to 45.79 mm3 and 72.8 to 65.45 g, respectively. Also, the static coefficient of friction on all surfaces increased significantly during the storage time.
Leila Momenzadeh; Ali Asghar Zomorodian; Darioush Mowla
Abstract
In this search drying characteristics of green pea (Pisum satium) with an initial moisture content of 76% (db) was studied in a fluidized bed dryer assisted by microwave heating. Four drying air temperatures (30, 40, 50 and 60ºC) and five microwave powers (180, 360, 540, 720 and 900W) were adopted. ...
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In this search drying characteristics of green pea (Pisum satium) with an initial moisture content of 76% (db) was studied in a fluidized bed dryer assisted by microwave heating. Four drying air temperatures (30, 40, 50 and 60ºC) and five microwave powers (180, 360, 540, 720 and 900W) were adopted. At each drying operating conditions the volume of green pea was calculated by measuring the three principal characteristic dimensions and the variation of the ratio of mean diameter of the kernel to its initial mean diameter was investigated for different operating conditions. It has been shown that power of microwave and temperature of drying could reduce the shrinkage of particles considerably. Furthermore, in this study, the application of Artificial Neural Network (ANN) for predicting the drying time (output parameter) was investigated. Microwave power; drying air temperature and green pea moisture content were considered as input parameters for the model. An ANN model with 4 neurons was selected for studying the influence of transfer functions and training algorithms. The results revealed that a network with the logsig transfer function and trainrp back propagation algorithm made the most accurate predictions for the green pea drying system. In order to test the ANN model, (RMSE), (MAE) (SE) were calculated and found that the random errors were within and acceptable range of ±5% with correlation coefficient (R2) of 98%.
Keywords: Green pea, Fluidized bed dryer, Microwave, Artificial Neural Network
Gholam Reza Mesbahi; Ali Asghar Zomorodian; Mojtaba Dadashzadeh; Asgar Farahnaki
Abstract
In recent years immense interest has been focused on the use of solar dryers especially when taking into consideration economical and ecological aspects and increasing in fuel costs. The aim of this study was to compare the qualitative factors of raisins made by five different drying methods. At the ...
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In recent years immense interest has been focused on the use of solar dryers especially when taking into consideration economical and ecological aspects and increasing in fuel costs. The aim of this study was to compare the qualitative factors of raisins made by five different drying methods. At the first step, pretreatments were applied to grapes (Var. Sultanas) and then the grapes were dried by five methods, including open-sun drying, shade drying, drying by industrial cabinet dryer and two different modes of solar drying namely mixed and indirect type. The shortest drying time was obtained with industrial cabinet drying, but mixed and indirect solar drying were more effective than open-sun drying and shade drying. Moisture content, acidity, sensory properties (color, texture, flavor and overall acceptance) and microbial level of the produced raisins were determined and compared. The texture of the raisin samples was evaluated by texture analyzer device as well. The color of the samples was measured and analyzed by a novel digital imaging method for measuring color of foods.The results indicated that the solar dryers were not only able to produce raisins similar to other drying methods but also the raisins produced by these dryers were in some qualitative factors (consumers overall acceptance and color) better than the other raisins.
Keywords: Raisin, Grape, Drying, Solar dryer, cabinet dryer.
