The Influence of Drying Temperatures and Methods on the Drying Characteristics of ‘IkanBakar’ Paste

Drying is one of the popular preservation methods in food products. This work was done to investigate the influence of the drying temperatures and methods on the drying characteristics of ‘ikanbakar’ paste. The ‘ikanbakar’ paste was dried by using oven drying and vacuum drying methods at temperatures of 50°C, 60°C and 70°C. The drying rate was estimated from the moisture content and drying time data. The drying curve showed the falling rate period as the drying rate decreased with increasing time. For colour analysis of the paste, the L* values from the oven drying method were lower than those from the vacuum drying method, ranging from 7.4210 to 7.2752. This showed that the colour of paste from oven drying was darker than vacuum drying. The mathematical models used to describe the drying curve of ‘ikanbakar’ paste were Lewis, Page, Two-term, and Midilliet. al. model. The performance of these models was evaluated by comparing their root mean square error (RSME) and chi-square (X²) values, and it was found that the most suitable model was the Two-term model. There were insignificant differences between the effective moisture diffusivity (Deff) values for the ‘ikanbakar’ paste in both drying methods.

Theoretical Estimation of Evaporation Heat in Paper Drying Process Based on Drying Curve

At present, the theoretical estimation of paper web’s evaporation heat is based on sorption isothermals. The measuring conditions are harsh, and the test speed is slow. This paper attempts to explore a theoretical method which can quickly determine the evaporation heat of paper web. During the new method, based on the measurement of the paper drying curve, the theoretical estimation model of paper evaporation heat was obtained by deducing the mechanism of heat and mass transfer. Compared with the traditional method based on sorption isothermals, the new model based on the drying curve has some advantages in measurement speed and easy access to basic data. Finally, the paper verifies the reliability of the model from two application scenarios of the laboratory and production line.

Application of basic drying theory to determine drying mass constants of selected seafoods

The drying of seafood could ensure increase in life span, minimization of storage space, ease of transportation, etc of the product. It is therefore, necessary to dry and know when to stop drying at an appropriate moisture content that would minimize associated challenges in promoting food security. In this study, selected sea foods, such as prawn and oyster were obtained and then dried to determine their drying mass constants using model equation developed based on basic drying principle. The value of the constants obtained would provide data bank to facilitates prediction of mass of the drying material at given time that would correspond to any desired moisture content, provided the initial moisture content of the material is known. The plots of moisture content against drying time, drying rate against drying time and moisture content versus were carried out. It was observed that increase in size of the drying material increased the drying time. Moreover, the drying rate curve resembles a typical drying curve. Hence, the experimental values obtained are reliable. Technical analysis showed that the drying mass constants for prawn and oyster are 0.2950 ± 0.0119 and 0.2453 ± 0.0476, respectively.

Effects of Contact Angle on the Hysteresis Effect of Soil-Water Characteristic Curves during Dry-Wet Cycles

The hysteresis characteristics of soil-water characteristic curves (SWCCs) under dry-wet cycling conditions are very important for understanding unsaturated soil properties, so it is crucial to propose an accurate and efficient method for predicting the hysteretic behaviors of SWCCs. To this end, this paper investigates the hysteresis characteristics of SWCCs in the full suction range of seven kinds of Hunan red clay with different initial dry densities by combination of the pressure plate method, the paper filter method, and the saturated salt solution method. It is found that there are, respectively, strong and weak hysteresis zones in the drying and wetting SWCCs under dry-wet cycling conditions. By combining this feature and based on the drying curve, the soil volume and contact angle changes during the drying and wetting processes are employed to predict the hysteretic behaviors of SWCCs. To verify the validity of the prediction method, the predicted curves of the samples with different initial dry densities are compared with the measured curves. The results show that in the strong hysteresis zone, the hysteresis characteristics of the drying and wetting SWCCs are mainly resulted from the changes in the soil pore structure; in the weak hysteresis zone, the hysteresis characteristics are mainly influenced by the changes in the receding and advancing contact angles corresponding to the drying and wetting processes. The Young–Laplace theory is used to transform the changes of contact angle during the drying and wetting processes into the proportional relationship k of matric suction, and the corresponding wetting curve is obtained by smoothing the drying curve. It is found that the prediction effect in the high suction part (the strong hysteresis zone) is better than that in the weak hysteresis zone, which confirms that the hysteresis effect of SWCCs in the high suction part is influenced by the contact angle. Our proposed method can greatly reduce the test period and has a significant practical application value, which provides a new idea for the prediction of SWCCs under dry-wet cycling conditions.

Modeling the soil-water retention curves for highly deforming soils

A porous-solid model based on the grain and pore size distributions of the soil is coupled with a mechanical model to simulate the soil-water retention curves while the material is deforming. During the determination of the main drying curve, the soil is subjected to high suctions which induce important volumetric deformations. These volumetric deformations modify the pore size distribution of the sample affecting both the drying and the wetting retention curves. Although, most deformation occurs at drying, the drying curve is only slightly affected by soil deformation. In contrast, the wetting curve shows important shifting when volume change is considered.

PRESSING AND DRYING PASTA

The article is devoted to the topic of pasta and such technological processes of their production as kneading pasta dough, pressing or forming pasta, drying finished products. The characteristic features and defining parameters for each of the processes are described. The main parameters that affect the quality of the finished product for the technological process of kneading the dough are humidity, temperature and the process of vacuuming the dough, for the process of forming pasta – pressing pressure and humidity of the dough, for the drying process-temperature, speed and humidity of the drying air. The character of the dough movement in the screw chamber and the pressing head during the molding of pasta is described, the drying process of pasta is considered, the drying curve of pasta is shown.

Application of microwaves in the convective drying of ceramic

The paper demonstrates microwave and convective drying processes in different combinations of kaolin cylindrical samples in laboratory scale. Analysis of the kinetics and sample temperature evolution show that the moment of application and electromagnetic field duration have the biggest influence on characteristics of the drying curve and quality of dried material. Dried samples were subjected to strength tests using the Brazilian method in order to determine the relation between its quality and different drying programs. Keywords: ceramic, convective drying, microwave drying, strength test.