Search

This study aimed to investigate the effects of FD (freeze drying), USVD (ultrasound‐assisted vacuum drying), HAD (hot air drying). and IRD (infrared drying) methods on drying behavior, total phenolic antioxidant activity, individual phenolic distribution, rehydration capacity, Scanning Electron Microscopy image, and color quality of Asian pear. HAD showed the longest drying period with 420 min and followed by USVD with 345 and IRD with 240 min. The method difference had a significant effect on the total phenolic and antioxidant activity values of the samples (p < 0.05). The TPC, DPPH, and CUPRAC value were found as 111.59–316.40 mg/100 g GAE, 336.94–559.41 mg/100 g TE, and 161.00–859.73 mg/100 g TE, respectively. Samples dried with FD showed the highest TPC and AA values, followed by USVD, IRD, and HAD. The effect of drying techniques on the distribution of phenolic compounds was found to be significant (p < 0.05). HAD and the IRD process caused a decrease in the amount of all identified phenolic compounds. While USVD caused an increase in the amount of Chlorogenic acid, FD did not cause a significant change. Higher HMF results were found in samples dried via IRD followed by HAD. While the porous structure was preserved in the samples dried with FD and USVD, the porosity structure of the samples dried with HAD and IRD completely disappeared. FD and HAD showed the highest and lowest rehydration capacity, respectively. FD and USVD showed lower color change than IRD and HAD. The results of this study showed that USVD and FD can be used as an alternative method to HAD in drying Asian pear. Practical Application: Pear fruit is one of the most consumed fruits worldwide. Pear fruit is very sensitive to microbial and enzymatic degradation due to its high sugar, bioactive component, and moisture content. To increase the shelf life of the pear fruit and to ensure consumption throughout the year, it must be subjected to a preservation technique. Drying is one of the main methods used to extend the long shelf life of fruits and vegetables. Undesirable changes may occur in the quality characteristics of fruits during drying. Therefore, determining the appropriate drying method is vital for the quality of the final product. In this study, the effects of different drying methods on many quality characteristics of pear fruit were investigated. This study has the potential to provide a new perspective on the drying of pear fruit. [ABSTRACT FROM AUTHOR]

The effect of pretreatment and infrared power on drying characteristics of apricot was investigated. The apricots were dried at 62, 74, 88 and 104 W infrared powers. It is observed that drying characteristics of apricot were greatly influenced by pre-treatment and infrared power. To select the most appropriate thin-layer drying model for drying process, ten mathematical drying models were fitted to the experimental data. Midilli et al. model satisfactorily described the drying kinetics of apricot. Effective moisture diffusivity ( Deff) ranged from 2.37 × 10−9 to 6.23 × 10−9 m2/s and calculated using the Fick's second law. The values of Deff increased with the increase of infrared power. Activation energy was estimated by a modified Arrhenius type equation and found to be 1.63 and 1.67 kW/kg for control and SMB samples, respectively. Practical Applications Apricot is good source of health-promoting compounds such as vitamins, polyphenols, carotenoids and natural salicylic acids. Due to both their seasonal and perishable nature, apricots should be subjected to some form of preservation in order to make them available for later consumption. Drying is one of the most common methods used for apricot processing. Infrared drying has gained popularity as an alternative drying method for a variety of agricultural products. Compared with hot air drying, infrared radiation heating offers many advantages such as greater energy efficiency, heat transfer rate and heat flux, which results in reduced drying time and higher drying rate. The main objectives of this study were to investigate the effect of pretreatment and infrared power on the drying time, fit the experimental data to ten thin-layer drying models and compute effective moisture diffusivity of apricot halves. [ABSTRACT FROM AUTHOR]

The effect of different infrared powers on the drying kinetics of carrot slices was investigated. The carrot slices were dried at 62, 74, 88, 104 and 125 W infrared powers and constant slice thickness of 0.5 cm. The results showed that the infrared power has a significant effect on the drying and quality characteristics such as rehydration and color. The whole drying process occurred within the falling rate period. Six thin-layer drying models were fitted to the experimental data. The Midilli et al. model was best fitted to the experimental data. Fick's law of diffusion was used to determine the effective moisture diffusivity, which varied between 2.45 × 10-9 and 7.38 × 10-9 m²/s. Activation energy was estimated by a modified Arrhenius type equation as 4.247 kW/kg. [ABSTRACT FROM AUTHOR]

The effect of different infrared power levels on drying kinetics of red kidney bean seeds was investigated. The bean seeds were dried at 83, 125, 167 and 209 W infrared power levels and constant seed diameter is 1.14 cm. It is observed that drying characteristics of bean seeds were greatly influenced by infrared power. The drying data were fitted with 10 thin-layer drying models available in the literature. According to the results, Midilli et al. model is superior to the other models for explaining the drying kinetics of bean seeds. Effective moisture diffusivity was calculated and was between 1.75 × 10-9 and 1.02 × 10-8 m²/s within the studied infrared power level range. Activation energy was estimated by a modified Arrhenius-type equation and found to be 9.54 kW/kg. [ABSTRACT FROM AUTHOR]

Drying of pomegranate by-products that are formed at the instance of pomegranate juice processing was studied at 50, 60, 70 and 80 C while air velocity was 2 m/s. The results obtained show that moisture content of the by-product decreases with time and temperature. The drying process takes place mainly in the falling rate period. Several thin-layer drying models were selected to describe experimental drying kinetics data. The models were compared based on their coefficients of determination ( R2), reduced chi-square ( χ2) and root mean square error ( RMSE) between experimental and predicted moisture ratios. Consequently, the Midilli et al. model was selected as the best mathematical model for describing the drying kinetics of the pomegranate by-products. The effective moisture diffusivity of pomegranate by-product varied from 1.22 × 10−10 m2/s to 4.29 × 10−10 m2/s. The activation energy was calculated as 39.66 kJ/mol using Arrhenius-type equation. Practical Applications Pomegranate is an important commercial fruit crop that is extensively cultivated all over the world in tropical, subtropical and temperate zones. It is mainly consumed as a raw staple food and used to mix in jams, jellies, teas, beverages, and concentrated in syrups and liqueurs. The process of pomegranate juice production remains large quantities of pomegranate by-products such as peels and seeds. The by-products due to high initial moisture content are very sensitive to microbial spoilage. Drying is one of the preservation methods applied to agricultural products. The basic objective in drying agricultural products is the removal of water in the solids up to a certain level, at which microbial spoilage and deterioration chemical reaction are greatly minimized. Besides, knowledge of drying characteristics is important in the design, simulation and optimization of drying process. [ABSTRACT FROM AUTHOR]

The freeze drying is a suitable dehydration process for saffron that contains heat-sensitive volatile and aroma-yielding compounds such as crocin (act as a coloring agent), picrocrocin (responsible for the taste) and safranal (volatile oil that gives characteristic odor and aroma). The heat-sensitive volatile and aroma-yielding compounds of saffron can be more preserved using freeze drying in comparison with other conventional drying methods. In this study the freeze-drying characteristics of saffron was determined experimentally. The drying kinetics data were fitted to 10 different empirical diffusion drying models from literature to find the best model that represents the weight loss of saffron during the freeze drying. Among the models tested in this study, the Page model was found to be the best model in representing the drying kinetics of saffron during the freeze drying. Effective diffusivity found as 1.62 × 10−11 m2/s. Practical Applications Saffron, which has been intensively used for flavoring and coloring foods, dying textile and medical purposes since ancient times, is the most precious and expensive agricultural product in the world. Freeze drying, which is both slow and expensive, is the method of separation for high market value products. It has been shown that freeze drying can be used for dehydration of saffron with minimum safranal (main aroma component) and crocin (coloring agent) loss. High cost of freeze drying of saffron can be compensated by minimum loss of safranal and crocin contents in the final product. It is crucial to know the drying kinetics of saffron to determine the drying time under certain conditions. In this work, the freeze-drying kinetics of saffron were studied and the best empirical model that represents the weight loss of saffron during the freeze drying and effective diffusivity were determined. [ABSTRACT FROM AUTHOR]

The effect of different infrared power levels on drying kinetics of peach slices was investigated. The peach slices dried at 83, 125, 167 and 209 W infrared power levels and constant slice thickness of 0.5 cm. It was observed that drying characteristics of peach slices were greatly influenced by infrared power. To select the most appropriate thin-layer drying model for drying treatments, 15 mathematical drying models were fitted to the experimental data. Midilli et al. model satisfactorily described the drying kinetics of peach slices. Effective moisture diffusivity ranged from 1.68 × 10-10 to 1.68× 10-9 m²/s and calculated using the Fick's second law. Activation energy was estimated by a modified Arrhenius-type equation as 4.49 kW/kg. [ABSTRACT FROM AUTHOR]

The effect of different infrared power levels on drying kinetics of watermelon seed was investigated. The seeds dried at 83, 125, 167 and 209 W infrared powers. It was observed that the power level affected the drying and rehydration characteristics of watermelon seeds. Drying time reduced from 170 to 40 min as the infrared power level increased from 83 to 209 W. Midilli et al. and Hii et al. models are satisfactorily described drying kinetics. Effective diffusivity varied from 0.72 × 10−10 to 3.78 × 10−10 m2/s and activation energy was calculated as 15.45 kW/kg. The highest energy efficiency was found for the samples dried at 209 W. Practical Applications Watermelon is an important crop grown in the warmer regions of the world. The fresh or juice from watermelon is used for human consumption. It contains large quantities of seeds, which can be cooked, dried and served as snacks. Because of high initial moisture content, the watermelon seed is very sensitive to microbial spoilage. Drying is one of the preservation methods applied to agricultural products. The basic objective of drying agricultural products is the removal of water in the solids up to a certain level, at which microbial spoilage and deterioration chemical reaction are greatly minimized. Besides, knowledge of drying characteristics is important in the design, simulation and optimization of drying process. [ABSTRACT FROM AUTHOR]

In this work, bay laurel leaves were dried using pilot-scale, cabinet-type, convective dryer. Drying experiments were conducted using constant air velocity of 2 m/s and air temperatures of 50, 60 and 70 C. Drying rate increased with increase in air temperature and thus reduced the drying time. The experimental drying data were applied to 14 thin-layer drying models. Nonlinear regression analysis was performed to relate the parameters of the model with the drying conditions. The performance of these models is evaluated by comparing R2, χ2 and RMSE between the observed and predicted moisture ratios. Among all the models, Midilli et al.'s model was found to be the best for explaining the drying characteristics of bay laurel leaves. The effective moisture diffusivity ranged from 9.38 × 10−12 to 2.07 × 10−11 m2/s over this temperature range studied, with activation energy of 36.48 k J/mol for bay laurel leaves. Practical Applications Drying is the most important process to preserve agricultural products, because it has a great effect on the quality of the dried products. The objective in drying foods is the reduction of the moisture content to a level that allows safe storage over an extended period. Bay laurel plants are known for cosmetic industry, food and medicinal purposes. This study concerns the investigation of the drying characteristics and presents a mathematical model for thin-layer drying of bay laurel leaves. [ABSTRACT FROM AUTHOR]

The effect of different infrared power levels on the drying kinetics and rehydration capacity of tomato slices was investigated. The tomatoes were cut into eighths and dried at different infrared power levels. It was observed that the power levels affected the drying time and rehydration capacity. Drying time was reduced from 450 to 240 min as the infrared power level increased from 125 to 188 W. The experimental data obtained from drying study were fit with nine mathematical models to evaluate the drying kinetics of tomato slices. The fit quality of the proposed models was evaluated using the determination of coefficient, mean relative percent error, reduced chi-square and root mean square error. Among the nine drying models, the model of Midilli et al. showed the best fit of drying kinetics of tomato slices. Effective moisture diffusivity varied from 2.66 to 5.17 × 10−9 m2/s and was significantly influenced by infrared power. Practical Application Tomato is an important commercial vegetable, having the highest production figures of all the vegetables in the world. It is used to a great extent in the fresh state and in some processes as juice, puree, sauces, dried and canned varieties. Tomatoes are highly perishable because of their high moisture content; therefore, they need to be dried. Infrared drying has appeared as one of the potential alternatives to the traditional drying methods in obtaining high-quality dried products. Infrared drying characteristics of tomato slices were studied in this work. The effect of infrared power level on the drying kinetics and rehydration capacity of tomato slices was determined. [ABSTRACT FROM AUTHOR]

ABSTRACT The water absorption characteristics of dried green bell peppers were studied at hydration temperatures at 25, 50 and 75C. Prior to drying at 65C, green bell peppers were pretreated with ethyl oleate (AEEO) and citric acid (CITRIC) solutions. Initial rehydration rates increased with rehydration temperature for all samples and were highest for the AEEO pretreated samples. At all rehydration temperatures, the equilibrium moisture contents were highest for the pretreated with AEEO solution. The moisture diffusivity (D) was determined by using Fick's second law. The values of D varied from 16.8 to 32 × 10−8, 9.16 to 16.7 × 10−8 and 9.73 to 19.9 × 10−8 m2/s for AEEO, CITRIC and CONTROL samples, respectively, over the temperature range investigated. PRACTICAL APPLICATIONS The rehydration characteristics, which indicate the physical and chemical changes during drying process of a dried product, are used as a quality index. Therefore, drying conditions should be optimized to obtain the dried product with good rehydration characteristics. In the present manuscript, studies were conducted to probe the kinetics of rehydration of dried green bell peppers. The effect of pretreatment of green bell pepper with chemicals (ethyl oleate and citric acid) and rehydration temperature on the rehydration kinetics was studied. Important rehydration kinetic parameters were evaluated, which helped in successful modeling of the kinetics. [ABSTRACT FROM AUTHOR]

ABSTRACT The effect of pretreatments on drying characteristics of potato slices was investigated in a cabinet dryer. The experiments were conducted on potato slices with thickness of 8 mm at 65C with an air velocity of 2.0 m/s. Prior to drying, potato slices were pretreated with citric acid solution (1:25 w/w, 3 min, 20C) or blanched hot water (3 min, 80C). Besides, the untreated samples were dried as control. The shortest drying time was obtained with potatoes pretreated with citric acid solution. The drying data were fitted with ten mathematical models available in the literature. The results indicated that Midilli et al., modified Henderson and Pabis, Verma et al., two-term, parabolic and logarithmic models were found the better to describe the drying of potato slices. The values of effective moisture diffusivity were found to be range between 1.78 × 10−10 and 2.94 × 10−10 m2/s and influenced by pretreatments. PRACTICAL APPLICATIONS The pretreatment followed by air-drying may provide a practical method for the preservation of fruits and vegetables. The experimental study evaluates the pretreatment and drying conditions of potato slices. The objective of this study was to study the effect of pretreatments on the drying times and rehydration ratios, to fit the experimental data to 10 thin-layer drying models available in the literature, and to compute effective moisture diffusivity of samples. This research is useful for producers of dry potatoes. [ABSTRACT FROM AUTHOR]

ABSTRACT Grape leaves were dried in a thin layer under hot air at 40, 50 and 60C m/s in the a cabinet dryer. The drying rate curves showed that the drying of grape leaves was characterized by a single falling rate period. Drying of grape leaves was greatly influenced by air temperature. Eight mathematical models available in the literature were fitted to the experimental data. The Wang and Singh and Midilli et al. models gave the best fits for each drying curve; based on the statistical tests, namely, coefficient of determination ( R2), mean relative percent error (P), reduced chi-square (χ2) and root mean square error (RMSE). Fick's second law model was used to calculate the effective moisture diffusivity, which increased with temperature from 4.13 × 10−10 to 1.83 × 10−9 m2/s, with estimated activation energy value of 64.56 kJ/mol. The rehydration capacity was found to decrease with an increase in rehydration temperature. PRACTICAL APPLICATIONS Grape leaves are extremely perishable. Because of their short shelf life under normal ambient conditions of temperature and humidity, their preservation has assumed importance. Drying, which is the oldest of food preservation practiced by mankind, is the most important process to preserve agricultural products because it has a great effect on the quality of the dried products. The objective in drying foods is the reduction of the moisture content to a level that allows safe storage over an extended period. In this study, drying characteristics of grape leaves were studied in a convectional hot air-dryer. The effect of air temperature on drying and rehydration characteristics was determined. For the optimal products, the drying characteristics, namely drying time and rehydration capacity, are considered. [ABSTRACT FROM AUTHOR]

BSTRACT [ABSTRACT FROM AUTHOR]