Nazmi Izli

In this study, carrot samples that have different slice thicknesses (2 and 4 mm) were dried by applying ultrasound pre-treatment at different time periods (0, 20 and 40 min) and the changes in colour, rehydration, pH and °Brix values were examined. Besides, microstructures of dried samples under different conditions were observed through scanning electron microscopy images. Drying was carried out in a modified oven at temperatures of 60 and 70 °C with an air velocity of 1 m/s. A decrease in b*(green/red) values was observed due to the effect of drying. The highest rehydration ratio (6.930) was found in 2 mm thick carrot samples, which were dried at 60 °C and treated with ultrasound for 40 minutes. It was observed that pH and °Brix values changed from 6.705 to 6.120 and from 68.70 to 6.80, respectively. An increase in the change of product structure was observed as a consequence of the increasing duration of ultrasound pre-treatment. It was emphasized that ultrasound technology might be the appropriate method for drying the carrot sample.

In this study, garlic slices were dried with a new drying method, electrohydrodynamic‐hot air combined drying system, under different temperatures (55 and 60°C) and voltages (15, 20, 25, and 30 kV), and the effects of drying conditions on drying time, color parameters, rehydration capacity, energy values, and microstructure were investigated. In addition, experimental data were fitted into 10 different mathematical models that are widely used to select the appropriate model that could describe the drying behavior of garlic slices. The longest drying time required for constant moisture content was observed under 30 kV‐60°C treatment for 100 min, while the shortest drying time was observed under 15 kV‐55°C treatment for 160 min. Verma et al., Diffusion Approach, and Newton models were determined so as to find the most suitable model for the drying behavior of thin‐layer dried garlic samples at different temperatures and voltages. Increasing drying temperature caused a decrease in the a* and b* values of the garlic samples. The lowest energy consumption during the drying of the garlic slices was found at 30 kV‐55°C treatment combination. It was observed that the temperature and kV values have impact on the product microstructures.Practical Application: Drying is the preservation process to extend the shelf life of products. The traditional method is the most used one in the drying industry. The low energy efficiency of this method and the loss of quality due to the high contact of the hot air with the product have led to the research of new methods. Therefore, the electrohydrodynamic method is used as a new approach that results in high energy efficiency and a high‐quality product. As a result, integrating the electrohydrodynamic system into the hot air drying method will reduce the contact of the hot air with the product, thus prevents the negative effect of temperature and provides better quality products. In addition, this system can increase the drying efficiency and energy economy by reducing the drying time and energy consumption in drying procedure of garlic samples.

This study investigated the rehydration, water activity, pH, Brix, color, bulk density, tapped density, flowability, cohesiveness, wettability, solubility values, and microstructures of freeze-dried European cranberrybush powders. Additionally, experimental freeze-drying data were coupled to nine thin-layer models, and the logarithmic model was chosen to estimate the moisture ratio of European cranberrybush. The pH and Brix values were measured between 3.0–3.2 and 40.33–52.00 for different powder sizes, respectively. A significant difference was observed for the water activity values of different powders that were classified into different powder sizes (P < .05). Moreover, it was identified that all powders exhibited “low” cohesiveness and “fair” flowability. However, the results showed that the highest bulk density (0.440 g/ml), tapped density (0.563 g/ml), wettability (4386 s) and solubility (264 s) were obtained in the samples with a “>500 µm” powder size. According to the all scanning electron microscopy images, skeletal-like structures formed on the surfaces.

In this study, the effects of the electrohydrodynamic (EHD) drying method with needle and wire, the hot air method and a combination of the EHD-hot air methods on the drying kinetics, color, rehydration ratio and scanning electron microscope images of apricot samples were investigated. In addition, the experimental drying data were modeled using ten different mathematical thin layer drying models. It was determined that the rehydration ratio values of the samples dried with the combination of EHD and hot air were generally higher than the rehydration ratios of the samples dried with hot air or EHD only. Samples from all the drying methods were compared with fresh samples; the color parameters were affected, and scanning electron microscopy images revealed the different physical changes in the microstructure of the products. As a result, it is determined that EHD technology can be used as an alternative drying method suitable for apricot samples.

In this research, the effects of convective drying method (60, 70 and 80 °C) and microwave drying method (160 and 350 W) on the drying characteristics, color, rehydration and microstructure properties of ginger has been examined. For the purpose of choosing the most appropriate thin-layer drying models in terms of the drying applications, nine mathematical models have been applied on the experimental data. Pursuant to the assessment of the statistical tests, models of Diffusion Approach, Midilli et al. and Page that represent drying characteristics are found to be better than other models. Drying applications have affected the color values of all fresh ginger samples. Results indicated that browning degree increases as drying temperature and microwave power rise. The samples dried at 60 °C has the maximum rehydration ratio while the samples dried at 80 °C has the minimum rehydration ratio. Scanning electron microscopy visuals have ascertained that the deterioration of the ginger samples remarkably surged due to the rise in either drying temperature or microwave power. Applying the convective and microwave techniques as an alternative drying method for ginger samples is possible.

In the present study, the effects of intermittent microwave-vacuum drying on the “Deveci” pear in terms of the drying kinetics, mineral content, protein content, rehydration ratio, color, energy, specific energy and microstructure were investigated. According to the drying treatments,...

The effect of microwave‐vacuum drying on drying characteristics, protein, mineral content, and color of the apple was investigated in this study. Eight different drying treatments were applied with using levels of microwave power (200 and 300 W), vacuum conditions (200 and 400 mmHg), and pulse ratios (PR = 1 [Continuous] and PR = 2 [30 s t_on/30 s t_off]). Based on the drying settings used, increasing microwave power, vacuum treatments, and decreasing pulse ratio provided shorter drying time. The Page model gave a high fit of statistical values at all data points used to describe the drying kinetics of dried apple samples. At the 300 W–200 mmHg–PR = 2 application, the quantity of potassium was found to be the highest compared with that of the other drying conditions. The protein rate of dried apples was higher than the fresh samples because of water loss. The lowest effect on L* (lightness [78.27]), a* (green/red [10.70]), and b* (blue/yellow [32.72]) values were observed in samples dried at the 200 W–400 mmHg–PR = 2, 300 W–200 mmHg–PR = 1, and 200 W–200 mmHg–PR = 2, respectively. As a conclusion, the treatment of 300 W–400 mmHg–PR = 1 was found most effective with a shorter drying time (30 min) and high protein content (2.5%).Practical applications: Apple (Malus domestica L.) is one of the most important fruit due to its nutritional composition and the presence of biologically active compounds that provide positive effects on human health. Therefore, apple is grown and farmed extensively in most agricultural areas around the world. Drying is one of the oldest methods of food preservation. Dried apple can be not only stored longer, but also used as packaged snacks and integral breakfast foods. Combining microwave and vacuum drying offers rapid and uniform drying, which can be used to dry food products on a commercial scale. In addition, application of intermittent microwave‐vacuum technology in the drying of apple can result in significant improvement in quality.