DRYING CHARACTERISTICS OF CORN IN FLUIDIZED BED DRYER

A batch fluidized bed dryer was carried out for corn drying. Drying characteristics of corn were investigated The experimental results indicated that moisture transfer inside a corn kernel was controlled by internal diffusion by the following conditions : inlet hot air temperatures of 120 - 200 °C, superficial air velocities of 2.2- 4 m/s, bed depths of 4 - 12 cm, fraction of air recycled of 0.5 -0.9 and initial moisture content of corn of 43 % dry-basis. The Wang and Sing equation could describe in accordance with the results. Inlet hot air temperature and specific air flow rate were independent variables for drying constant model in the Wang and Singh equation.     

Mathematical model of pork slice drying using superheated steam

Superheated steam has received much attention as an effective technique for drying purposes because it produces dried products with high quality attributes. Although currently there are a number of works reporting the development of a mathematical model of superheated steam drying, they do not use a numerical method to estimate the effective moisture diffusivity value (D_eff value) of the product. The purposes of this work, therefore, were to develop a semi-empirical model for estimating the D_eff value of pork, and for predicting the evolution of the moisture content and the center temperature of sliced pork during superheated steam drying. The model was based on mass and energy-balance equations and was divided into three periods: heating up, constant drying rate and falling drying rate period. It was solved using an explicit finite difference method and used a grid search method to estimate the D_eff value of pork. The predicted results were compared with the experimental data of superheated steam drying of seasoned and unseasoned pork with slice thicknesses of 1 and 2 mm at a drying temperature of 140 °C. The comparison results showed that the developed model could estimate the ranges of the D_eff value of pork fairly well (D_eff = 3.311-12.471 × 10⁻¹⁰ m²/s for seasoned pork, and 4.200-15.056 × 10⁻¹⁰ m²/s for unseasoned pork) and could reasonably predict the evolution of the moisture content of the sliced pork. The predicted center temperature of the sliced pork was higher than the experimental data in the heating up period and in the first 5 min of the falling drying rate period, but it agreed well in the constant drying rate period and after the drying time of 10 min. Moreover, it was found that the slice thickness and the seasoning had an influence on the drying curves only in the constant drying rate and falling drying rate period.     

A Comparative Study of Pork Drying Using Superheated Steam and Hot Air

Drying with superheated steam and hot air were comparatively studied for pork. Transport, physical, and chemical properties, i.e., effective diffusivity, color, microstructure, and rehydration ability, were investigated. The experimental results have shown that the decrease of pork moisture content in an early drying time was more rapid in superheated steam than in hot air and appeared to be lower in a latter time. The pork surface as examined by SEM was noticeably different for the samples dried by superheated steam and hot air. The fewer pores at the surface of superheated steam-dried pork caused a slower water penetration into the interior during rehydration, in addition to the lower drying rate. The color of the product from superheated steam was a relatively more intense brown than that obtained from hot air as presented by a lower L* value and a higher a* value.     

Performance Evaluation of Top-Spray Fluidized Bed Coating for Healthy Coated Rice Production

Coating with top-spray fluidized bed at inappropriate operating condition not only provides low product quality but also leads to low coating efficiency and improper energy consumption. The objective of this study was therefore to study the effects of superficial air velocity (Vf), atomization air pressure (Ap), and recycled exhaust air (Ra) on the performance of top-spray fluidized bed coating (TSFBC) in terms of product quality, coating efficiency (CE), and energy consumption for producing turmeric extract coated rice (TECR). The experimental results showed that the operation of TSFBC without Ra provided the final moisture content (MC) of TECR lower than 12 % (wet basis (w.b.)) for all Vf’s and Ap’s. The lowering final MC of TECR below 11.8 % (w.b.) led to the fissure of all TECR kernels. The Ra with 80 % could significantly reduce the number of fissured kernels and the energy consumption of electric heater by 41.7–46.5 %. The operation of TSFBC at low Vf, i.e., 2 m/s, resulted in high number of uncoated white rice kernels (UCWR) for all Ap’s and Ra. When the Vf was increased to 2.5 or 3 m/s, the number of UCWR was significantly reduced and the value of CE was higher than that at 2 m/s. At such both velocities, the Ap and Ra insignificantly affected the CE but the Ra slightly affected the number of UCWR.     

Quality changes of shrimp during boiling in salt solution

ABSTRACT:  Boiling shrimp in salt solution is an important step during the production of dried shrimp. In this study the effects of various boiling parameters, namely, concentration of salt solution (2, 3, and 4% w/v), mass ratio of shrimp to salt solution (1:2 and 1:3), boiling time (1, 3, 5, and 7 min), and shrimp size (small and large), on the various quality attributes of shrimp were investigated. The quality of boiled shrimp was evaluated in terms of its salt content, moisture content, which is in turn related to the other qualities, namely, protein content, colors, shrinkage, and texture (hardness and toughness), as well as microbiological quality. It was found that higher concentration of salt solution and longer boiling time and lower mass ratio of shrimp to salt solution led to higher salt content of shrimp but to lower levels of moisture and proteins, leading to higher values of hardness, toughness, shrinkage, and color changes of shrimp. However, the mass ratio of shrimp to salt solution alone did not significantly affect any qualities of boiled shrimp ( P > 0.05). It was found that the minimum boiling time of 3 min was enough to reduce the number of microorganisms to a safe level and inactivate enzymes causing melanosis in boiled shrimp.     

Effect of Osmotic Treatment on Drying Kinetics and Antioxidant Properties of Dried Mulberry

Air drying is widely used in fruit preservation. However, this causes a reduction in the nutritive value of the product. Osmotic treatment has been used as prior to drying. The objectives of this research were to study osmotic treatment in combination with air drying of mulberries and to evaluate the influence of different osmotic solutions on drying kinetics, reaction kinetics, and antioxidant capacity, with a focus on anthocyanins and phenolics. Mulberries, either untreated or osmotically treated with sucrose, sorbitol, and maltose, were dried in a tray dryer at 60°C with a velocity of 1 m/s. The drying kinetics of mulberries were explained using the Page model based on the R ² values, which ranged from 0.985 to 0.993, and E _s , which ranged from 0.031 to 0.091. Air drying caused degradation of anthoyanins and phenolics, which followed a zero-order reaction with R ² values ranged from 0.866 to 0.996. Osmotic treatment with maltose was found to be a good treatment for mulberry drying and preserved the phenolic and anthocyanin contents and provide high antioxidant capacity.     

Comparative Evaluation of Hot-Air and Superheated-Steam Impinging Stream Drying as Novel Alternatives for Paddy Drying

An investigation was conducted on impinging stream drying of moist paddy using hot air and superheated steam as the drying media. Drying experiments were divided into two parts: namely, one-pass and two-pass drying. The volumetric water evaporation rate, volumetric heat transfer coefficient, and specific energy consumption of the drying system at various conditions were assessed; in the case of superheated-steam drying, the effect of steam recycle was also assessed. The quality of dried paddy was evaluated in terms of color, head rice yield, and degree of starch gelatinization. In the case of one-pass drying, an increase in the drying temperature led to a significant increase in the volumetric water evaporation rate and volumetric heat transfer coefficient. On the other hand, in the case of two-pass drying, an increase in the drying temperature led to a significant decrease in the volumetric heat transfer coefficient; the volumetric water evaporation rate was not significantly affected, however. The specific energy consumption decreased with an increase in the drying temperature. At the same temperature, using superheated steam as the drying medium led to lower specific energy consumption; higher level of steam recycle also led to more energy conservation. The color of the dried paddy was not affected by the change in the drying temperature; superheated-steam-dried paddy was redder and more yellow than the hot-air-dried paddy. An increase in the drying temperature led to decreased percentage of head rice yield. Superheated-steam drying helped enhance the level of starch gelatinization in comparison with hot-air drying at the same temperature. Nevertheless, drying at the highest tested temperature led to a lower level of starch gelatinization.     

Bagasse saving and water recovery in cogeneration system using superheated steam dryer

The cogeneration system in sugar factory uses bagasse with high moisture content as the fuel for the boiler, which results in low boiler efficiency. The system also produces superheated steam, which is extracted from the turbine, and mixed with cooling water to produce saturated steam required by the evaporation system. The potential use superheated steam to reduce bagasse moisture content is ignored in the standard practice of the sugar factory. In this article, an investigation is made into the improvement of the cogeneration system by using superheated steam dryer to reduce the moisture content of bagasse. Mathematical models are developed for the typical system without superheated steam dryer and the improved system with superheated steam dryer. They are then used to compare the performances of both systems. It is found that, under the condition that the required steam flow rate for the evaporation process and the power output are the same, the improved system requires less bagasse consumption, and has larger energy utilization factor. In addition, water that would be lost with flue gases in the typical system is recovered in the improved system.