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 96oC) 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 76oC seemed to be the best condition for drying of Kabkaab rutab.

In this study, Mazafati date samples were dried using a cabinet drier at five temperatures (50, 60, 70, 80 and 90 oC) 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 oC have negative effects on color of the date samples. Therefore, drying temperature of 70 oC was found to be the optimum condition for drying process of Mazafati date.

In this study, mathematical modeling of hot air-drying of thin-layer papaya (Carica papaya L.) slices with 5±1 mm thickness pretreated in osmotic solution (50% sucrose) was investigated. Thin-layer drying was conducted under three different drying temperatures of 40, 50 and 60oC at a constant air velocity of 0.9±0.1 m/s and absolute humidity of 0.6±0.02 g of water/kg of dry air. It was found that the drying process occurred in falling rate period over the drying time. The osmosis dehydration characteristics obtained by solid gain (SG), water loss (WL) and weight reduction (WR) parameters that increased with increasing immersion time. The effective diffusivity for papaya slices was within the range of 2.13×10-9 to 4.84×10-9 m2/s over the temperature range. The activation energy was 38.63 kJ/mol indicated the effect of temperature on the diffusivity. Based on the statistical analysis using coefficient of determination (R2) and root mean square error (RMSE), it was concluded that the best model in terms of fitting performance for hot air-drying of papaya pretreated in osmosis solution in all temperature range was Midilli et al. model.

Dehydration, as one of the practical ways to increase the shelf-life and applicability of yoghurt in various foodstuffs, is normally done by freeze drier (FD) which is an expensive and time-consuming process. For these reasons, in the present study the capability of microwave–vacuum drier (MVD), as an alternative process, was investigated. For doing so, the fat free yoghurt samples of 2.2, 4.2 and 6.2 mm were dehydrated under various combination of absolute pressures (60, 200, 400, 600, and 800 mbar) and microwave powers (35,130, and 260 W) using a lab scale drier designed in our lab. Based on our findings, the drying time of yoghurt in microwave–vacuum drier for thickness of 2.2 mm was considerably (80%) shorter than commercial freeze-drier. In addition, the dependency of the drying time to absolute pressure was much less than microwave power and yoghurt thickness. Furthermore, except the color and bulk density, the rest of the qualitative parameters of yoghurt powders dehydrated by MVD and FD methods were almost similar. It should be noted that the highest resemblance in terms of quality and color indices between FD and MVD powders was seen at combination of low microwave power and low absolute pressure (35 W, 60 mbar). All in all, the findings of this study showed the capability of MVD for production of yoghurt and other food powders and this technique can be introduced as a potential alternative for FD.

This research focuses on the need for preserving fruits in rural areas to prevent waste. The solar drier is made of vital chambers i. e. the concentrator chamber (that harvests the solar irradiance), the transport pipe (that transports the heat generated by convection) and hanger chamber (where the fruits are placed). The temperature within the concentrator chamber and hanger chamber was monitored. The design allowed heat transfer by convection from the collector to the chamber at an efficiency of 92 %. The design allowed the temperature build up in the solar collector to be transported faster through hanger chamber with the help of incorporated detachable low power dc fan. This arrangement makes the dryer to either operate in the natural convection dryer mode (without the fan) or as a forced convection dryer (with the fan attached). It is observed that the forced convection provided higher air in-flow and hence greater drying capability. However, regions with moderate precipitation may have challenges of delayed fruit drying and growth of microorganism over the surfaces of the dried fruit.

In order to reduce leachate from food waste a conventional tray cabinet dryer was designed and built, and the drying process of these wastes was investigated. A 2. 7 kW heater equipped with an axial fan was used as the heating source. The experiments were performed at three temperatures of 50, 60, and 70 °C and three air velocities of 1, 1. 5, and 2 m/s with a thickness of 3 cm. A conventional tray was used for drying. The Drying kinetics, effective moisture diffusivity and activation energy during drying of food waste were obtained. Results showed that improving air distribution in the back of the tray and no passing air on the sides of the tray causes that increase the drying rate significantly. The minimum drying process was occurred in temperature of 70°C and air velocity of 2 m/s at the 120 min. Effective moisture diffusivity of waste food during the drying process was in the range of 2. 74×10-9-3. 65×10-8 m2/s. The values for activation energy have ranged from a minimum of 21. 6 kJ/mol in 1. 5 m/s air velocity up to a maximum of 64. 0 kJ/mol in 2m/s air velocity.

In this paper a method of using neural network in order to model nonlinear systems whose input and output data are measurable by time series is being considered. Feed back neural network technique is applied in order to consider the specifications and dynamic behavior of the system in the modeling process. This method is applied to model a batch fluidized bed drier. In present report it is shown that unlike the classic techniques, this method is able to predict the system behavior in all the stages of the process, such as; high humidity increase, high and low humidity decrease. In addition, the proposed technique has considerable accuracy and is free from using physical specifications in calculations and also using a very fast computation technique. The model is tested by applying a totally different set of data from those which used for training the network; it is observed that the modeling results for this nonlinear dynamic process is totally authentic.

In this study, the moisture content of kiwifruit in vacuum dryer was predicted using artificial neural networks (ANN) method. The drying temperatures (50, 60 and 70oC), vacuum pressures (500, 550 and 600 mmHg), thicknesses of kiwifruit slices (3, 5 and 7mm) and drying times were considered as the independent input parameters and moisture content as the dependent parameter. Experimental data obtained from vacuum drying process, were used for training and testing the network. Several criteria such as training algorithm, learning rate, momentum coefficient, number of hidden layers, number of neurons in each hidden layer and activation function were given to improve the performance of the ANN. The total number of hidden layers and the number of neurons in each hidden layer were chosen by trial and error. The best training algorithm was LM with the least MSE value. Optimum values of learning rate and momentum for the ANN with GDM training algorithm were set at 0.2 and 0.05, respectively. The optimal topologies were 4-20-1 with Tansig activation function and MSE values of 0.0016 and 4-15-20-1 with Logsig activation function in both hidden layer and MSE values of 0.000147. The correlation between the predicted and experimental values in the optimal topologies was higher than 99.75%.

Wheat starch is the most common type of starch in Iran as well as many other parts of the world with enormous applications in food and non-food products. To improve its physicochemical properties or create new functionalities, starch can be modified by changing its molecular structure. Amongst different methods for starch modification, physical methods have received more attention recently. Pre-gelatinization of starch is a physical method to modify the properties of native starch. The main aim of this research was to study the physicochemical properties of pre-gelatinized wheat starch produced using a small scale industrial twin drum drier. The results indicated that drum drying destroyed native starch granules, degraded molecular structure and reduced the degree of crystallinity of starch. Pre-gelatinized starch (PGS) showed cold water viscosity at 25oC, while native wheat starch was not able to increase the viscosity under this condition. It also increased water absorption and swelling of the starch compared to its native counterpart. Pre-gelatinized wheat starch can be used as a thickening agent in instant food products to eliminate heating stage in their production or in manufacturing of the products sensitive to high temperature.

In this study, the effect of using heat exchanger on increasing the performance of the collector and solar dryer was investigated. Moreover, computational fluid dynamics (CFD) method was used to simulate the heat transfer and distribution of thermal counters in the cabinet solar dryer equipped with heat exchanger with two outlets and porous plate. The results showed that using heat exchanger with half air mass flow rate for the first and second outlets (0. 009 kg/s) increases the efficiency of the dryer up to 10. 2% related to the dryer without heat exchanger. Excessive air flow rate inside the heat exchanger decreases the performance of the solar cabinet dryer. The results of the comparison between the CFD and experimental data shows that CFD method with 6. 9% of relative error has a good correlation with the experimental data. Using heat exchanger has no adverse effect on the color quality of dried tomato samples.