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    In this research using a digital camera, a PC and a graphical software; a simple and low cost method for the evaluation of colour of food materials is introduced. Analysis of digital pictures of the surface of samples can give L, a, b Hunter colour parameters and colour distribution. Drying of Kabkaab rutab in a range of temperatures (56, 66 76, 86 and 96 ˚C) and times using a cabinet drier was investigated. colour changes of the dried samples and the control were evaluated by analysing the  digital pictures of the samples and showed that increase of temperature and time caused a systematic reduction of L, a, and b values. Taken into account colour changes of the samples and their drying rates at different temperatures, the drying temperature of 76 ˚C seemed to be the best condition for drying of Kabkaab rutab.    

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Aim of pre-treatment drying of mulberry was to reduce the moisture content to a level that allows safe storage over an extended period. In this research after physical and chemical pretreatments, mulberry was dried industrially (cabin dryer). Non Enzymatic Browning was tested at 440 nm by spectroscopic method. Organoleptic tests were done by trained panelists. Hardness and cohesiveness of dried mulberries were measured by a texture analyzer. Statistical method was completely randomized design with 10 treatments and three replicates. The results showed that least intensity of brown color was in pretreatment of fruits with potassium meta bisulfate 0.5%  +calcium chloride %1. The highest water absorbance was in ethyl oleate 2%.   Panel tests showed highest score for overall acceptance in pretreatment of fruits with ethyl oleate 2% +potassium meta bisulfate 0.5%, highest score for texture with ethyl oleate 2% +calcium chloride %1, highest score for color with ethyl oleate 2% +potassium meta bisulfate 0.5%, highest score for odor with ethyl oleate 2% +citric acid %1 and also ethyl oleate 2% +ascorbic acid1%   and highest score for taste with ethyl oleate 2% +calcium chloride %1. Totally it is concluded that ethyl oleate 2%  , ethyl oleate 2% +citric acid %1, oleate 2% +ascorbic acid1%  , ethyl oleate 2% +potassium meta bisulfate 0.5% and oleate 2% +calcium chloride %1  are the best  pretreatment for drying of white mulberry.  

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    Aim of pre-treatment drying of mulberry was to reduce the moisture content to a level that allows safe storage over an extended period. In this research after different combination of ethyl oleate pretreatments, mulberry was dried industrially (cabin dryer). Dried mulberries packed in polyethylene and polystyrene and preserved for 5 months in 20ْ c. Non Enzymatic Browning was tested at 440 nm by spectroscopic method. Organoleptic tests were done by trained panelists. Hardness, Cohesiveness, Springiness and Chewiness of dried mulberries were measured by a texture analyzer. Statistical method was factorial in frame of completely randomized design with two factors and three replicates. Factor A was different pretreatments and factor B was packaging type. The results showed that Least intensity of brown color was in dried white mulberry pretreated by ethyl oleate 2% +ascorbic acid1% and then in ethyl oleate 2% +potassium meta bisulfate 0.5%  treatments . The lowest total count was in white mulberry in ethyl oleate 2% +potassium meta bisulfate 0.5%.  The results of Panel tests showed highest score for texture, color, odor, taste and overall acceptance in pretreatment of fruits with ethyl oleate 2% +potassium meta bisulfate 0.5%. The results of rheological tests showed that the highest score for chewiness was in white mulberry pretreated with ethyl oleate 2% +potassium meta bisulfate 0.5%. White mulberry pretreated and packaged in poly styrene had the lowest scores for brown color and total count after 5 months storage. Totally it is concluded that dried white mulberry pretreated with combination of ethyl oleate 2% and potassium meta bisulfate 0.5% and packed in poly styrene preserved its  qualitative, sensory and rheological characteristics after 150 days in 20ْc .  

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  In this study, Mazafati date samples were dried using a cabinet drier at five temperatures (50, 60, 70, 80 and 90 ˚C) and air flow rate of 1 m/s. Changes of total soluble solids, browning, pH, acidity and color parameters (L*, a* and b*) of date samples during drying were determined and compared. The results showed that total soluble solids, browning index and acidity increased and pH of date samples decreased. Moreover, L* and b* color parameters decreased and a* value increased. Overall, it was concluded that the moisture of Mazafati dates can be reduced by industrial drying. Furthermore, air temperatures of greater than 70˚C have negative effects on color of the date samples. Therefore, drying temperature of 70˚C was found to be the optimum condition for drying process of Mazafati date.  

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 Abstract

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Many research studies have been performed on forced convection (active) solar dryers for fruit and vegetables. A short survey of these showed that applying the forced convection solar dryer not only significantly reduced the drying time but also resulted in many improvements in the quality of the dried products. Active indirect and mixed-mode thin layer solar drying experiments were conducted on Sultana grapes. A combination of a solar air heater and a cabinet dryer was designed, constructed and tested for this product in the Agricultural Engineering Department at Shiraz University, Iran. Three air flow rates (0.085, 0.126 and 0.171 m3 s-1) and two types of drying systems (indirect and mixed-mode) were adopted. The south wall of the drying chamber was covered by a sheet of glass for mixed-mode and the glass sheet was covered with a thick sheet of cloth for an indirect solar drying system. Seven well-known thin layer drying models were used separately to fit the mixed-mode and indirect type experimental data for Sultana grapes. For experimental indirect data, the Modified Page model (r= 0.998, χ2= 0.000241) and for experimental mixed-mode data, the Page model (r= 0.999, χ2= 0.000169) showed the best curve fitting results with highest r (correlation coefficient) and lowest χ2 (reduced chi-square) values. The constants in these models explain the effects of drying parameters, air velocity and temperature. To take account of these effects, the best correlation equations between the constants and drying parameters were also introduced using multiple regression analysis.

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In this research drying kinetics, moisture diffusivity and determination of most appropriate mathematical modeling and activation energy of Mazafati dates species were studied under a cabinet solar dryer.Drying experiments were carried out at three air temperatures of 50, 65, and 80ºC and three air velocities of 1.0, 1.5, and 2.0 m/s. Effect of temperature and air velocity evaluated on drying time and shrinkage by using a completely randomized statistical design. Results showed that the effects of temperature and air velocity are significant on drying time. The average increase of temperature from 50ºC to 80ºC caused the drying time to decrease by 70.77%. For determination of most appropriate model, the highest value of R² and the lowest values of c² and RMSE were used. For mathematical modeling, eight empirical models were fitted on experimental data and the best model was selected. The result of regression analysis showed that Page model has the best fitting with data. Moreover, the lowest and highest value of moisture diffusivity were obtained as 4.309×10^-10 and 0.0188×10^-9  m²/s at temperatures of 80^°C and 50^°C, respectively. Also the values of activation energy in the drying of Mazafati dates species were found between 31.22 to 42.27 kJ/mol.