Passive Drying of Yum Tuber Slices (Dioscorea alata L.)

ABSTRACT Passive drying is a drying mechanism that utilizes sunlight in a drying chamber with natural air flow mechanism. The tool used is direct passive solar box dryer. Direct type passive drying is a drying mechanism in a drying chamber with an air flow mechanism where direct sunlight enters the drying chamber. This study was intended to determine the pattern of decreasing water content and moisture ratio of yum (Dioscorea alata L.) and the appropriate drying model. Passive drying of yum tuber slices is done in two stages. The first drying data is used to determine the most suitable drying model (biggest R2). While the second drying data is used to validate the accuracy of the model predictions obtained. The drying process is carried out by placing the sample at the top, middle, and bottom of the drying chamber. The samples used are two types of yum namely white yum and purple yum with a size of 3x3x1 cm. The models evaluated for compatibility are Newton, Henderson & Pabis, and Page. The results of the analysis show that the Page model with the equation MR = exp (-ktn) is the most suitable model to describe the pattern of decreasing water content and moisture ratio of yum. The values ​​of the Page equation constants are obtained as follows: k = 0.187249, n = 1.17272 and R2 = 0.999403. Keywords: Yum, Drying, Drying Model, Water Content

Selected Engineering Properties and Drying Behavior of Tendu Fruit

In this study, the selected engineering properties of tendu fruit (ripe and unripe) and drying of behavior of tendu fruit slices in different dryers at two temperature levels were investigated. The drying was conducted at 50°C and 60 °C for the slices of 1cm, 2cm, and 3 cm in tray dryer, vacuum dryer, and freeze dryer, respectively. The moisture ratio using modified page equation was used to study the drying behavior. The engineering properties such as bulk density, true density, Carr’s compressibility index, surface area, unit volume, angle of repose, and the coefficient of static friction were studied for tendu fruits , results showed a slight variation in values of ripe and unripe fruit. The porosity and Carr’s compressibility index for ripe and unripe tendu fruits were found (26.12% and 24.89 %) and (6.64 and 7.67), respectively. Whereas the proximate analysis did not found major differences in the ash, crude fat, crude fiber, and protein content values. The drying ratio for vacuum drying was found better results when compared to tray drying for all thickness of fruit slices. The tendu fruit slices of 1cm thickness at 60°C found better result in vacuum drying compared to tray drying and the best fit for modeling on the basis of X2, R2 and RSME also proved it. Freeze drying as a continuous drying process found the best quality of dried slices for all thicknesses with the final product moisture content between 7-10% (wet basis, wb).

Mathematical Modeling of a Cross-Flow Rice Dryer with Grain Inverters

Industrial-scale cross-flow dryers are commonly equipped with grain inverters to improve the uniformity of drying across the column thickness. While a few mathematical models have been reported that include the operation of grain inverters, such models were rarely validated with experiments comprising grain inversions. In this study, a mathematical model was developed to evaluate the impact of grain inverters on the uniformity of grain moisture content (MC) across the column in cross-flow dryers. To improve the accuracy of model predictions, the impact of using two thin-layer drying equations, the Newton and modified Page equations, in the model was also investigated. An experimental setup was fabricated to simulate grain inversion, and drying experiments were performed to measure rice MC and air temperature across the column thickness, which were then compared with model-predicted values. When the modified Page equation was used in the model, the model predictions matched the experimental observations more closely than when using the Newton equation. The model successfully predicted grain and air properties when 0, 1, and 2 grain inversions were used; the root mean square error between predicted and measured values of rice MC and air temperature were within 0.1 to 0.2 percentage points and 1°C to 4°C, respectively. Grain inversions were shown to improve the uniformity of drying in rice kernels; in the tested drying conditions, a single grain inversion produced more uniform drying than two or more grain inversions in the column. The presented results demonstrate the usefulness of the developed model in investigating the role of grain inversion in cross-flow drying of rice. As such, the model could be readily used to improve dryer design, particularly the number and arrangement of grain inverters, and optimize rice drying operations. Keywords: Deep-bed drying, Grain inverters, Mathematical modeling, Reversed airflow, Thin-layer drying.

Drying kinetics and microbiological quality of green onions

ABSTRACT Green onion (Allium fistulosum L.) is widely consumed and traded in Brazil as condiment. Because of the high yields in the region of Volta Redonda - RJ and the alternative of drying as a method for preserving the excess production, the objective of this study was to evaluate the drying process of green onions, considering the microbiological quality, and to develop the mathematical modeling of this process. Mathematical models to describe the drying of agricultural products were used to predict the phenomenon. The modified Page equation gave the best fit to the data. Microbiological quality was evaluated using the analysis of aerobic mesophilic bacteria, molds and yeasts. Dehydration at 60 ºC was the most indicated for green onions, with assured microbiological quality.

Drying Kinetics Of Ginger Rhizome (Zingiber officinale)

This paper presents the drying kinetics of ginger rhizome under blanched and nonblanched conditions using hybrid solar dryer and mechanical tray dryer at three temperature levels. The drying rate increases with the increase in drying air temperature and blanching also increases the drying rate. The drying rate depends on shape and size of the ginger rhizomes. The highest drying rate was found for sliced samples of ginger rhizome followed by splitted and whole root samples. Five thin layer drying models were fitted to the experimental data of blanched and sliced ginger rhizomes. The Page equation was found to be the best to predict the moisture content of sliced ginger rhizome in thin layer. The agreement between the predicted and experimental results was excellent. Colour of ginger rhizomes was slightly changed after drying. Lightness of ginger rhizomes decreased with an increase in drying temperature for all samples except sliced and blanched samples. For drying of ginger rhizome, it should be sliced and blanched and dried below 70°C for better quality dried products. Bangladesh J. Agril. Res. 38(2): 301-319, June 2013 DOI: http://dx.doi.org/10.3329/bjar.v38i2.15892

Creating an Application to Predict Operational Characteristics and Efficiency of Continuous Cross-Flow Corn Drying

The purpose of this study is to create a computer simulation which numerically predicts the drying conditions within a continuous cross-flow grain drying system. The model is based on a system of four partial differential equations using energy and mass balances for the air, grain, and moisture within the column. This simulation includes: (1) a graphical user interface for varying the operating conditions, (2) a numerical scheme for solving the system of equations based on a backwards finite difference scheme, and (3) graphical and tabular output data. The output includes graphs of moisture content, air temperature, and grain temperature inside the column, as well as the predicted energy consumption of the system. Using this program, the grain drying model is analyzed in order to gain insight towards the optimal operating conditions for the grain dryer. The study also makes adjustments to the model in order to improve accuracy and ease of use. In particular, the Page equation for single-kernel drying is implemented. Model assumptions are also analyzed for validity, and the solutions are verified using experimental data collected in a previous study. The overall goal of this research is to improve grain dryer design and optimize operating conditions in order to reduce energy costs, improve grain quality, and increase the understanding of deep bed grain drying models.

Convective Thin-Layer Drying Characteristics of Sesame Seed

Fundamental Information on Drying and Re-Wetting Characteristics of Agricultural Seeds Is Required in the Design and Aeration Systems as Well as in the Prediction of Drying Rate Using Various Mathematical Models. Thin-Layer Drying Experiments Were Conducted Using Air-Ventilated Oven to Simulate the Artificial Drying at Various Moisture Contents of Sesame Seed (6.9 to 18.2 % W.b) at Three Drying Temperatures of 40, 50 and 60OC. Five Drying Models Were Evaluated for the Thin-Layer Data. the Page Equation Fitted the Data Best, where Selection of the Best Model Was Obtained by Comparing the Coefficient of Determination (R2), the Standard Error of Moisture Content (SEM) and Mean Relative Percent Error (e) between the Experimental and Estimated Values. the Drying Rate of Sesame Seed under Drying Conditions Increased with Increased Temperature of Drying( 40 to 60OC) and Initial Moisture Content of Seed( 6.9, 11.5 and 18.2 % W.b). the Parameters “K” of the Page Model Increased with Increase in Temperature, while, Parameter ”n” Decreased with Temperature Increase and Increased with Increase in Moisture Content of Seed. the Effective Diffusivity Was Found to Be 2.32 X 10-11 M2s-1.

Improvement of paper properties of recycled unbleached softwood kraft pulps by poly(allylamine hydrochloride)

Polyelectrolytes containing amine functional groups such as PAH (poly(allylamine hydrochloride)) can be useful, under certain conditions, for improving paper strength. In this work, the charge density of PAH was determined at different pH and ionic strengths; PAH adsorption onto the cellulosic fibers was characterized, and the effects of low PAH dosage on the papermaking properties were evaluated. It was found that the ionization of PAH is complete in acid media, but it is partial and depends on the ionic strength in neutral media. The adsorption isotherms of PAH on a recycled pulp from kraft liner allowed us to determine the amount needed to saturate the adsorption capacity of the fibers. For the three ionic strengths analyzed, the swelling of the fibers decreased when PAH was added in an amount corresponding to saturation (0.23% PAH on dried pulp). Nevertheless, the swelling was recovered when the amount of PAH was the double the saturation level (0.46% PAH on dried pulp). At these levels of addition, the papermaking properties were clearly improved, especially compressive strengths SCT (short compressive test) and CMT (concora medium test). The Page equation of tensile strength showed that PAH improved the shear bond strength, while the relative bonding area slightly decreased.