Ragab Khir

Drying Characteristics and Quality of Rough Rice under Infrared Radiation Heating

Infrared (IR) radiation heating could provide a high heating rate and rapid moisture removal for rough rice drying. The objective of this research was to investigate the effect of the drying bed thickness on drying characteristics and quality of rough rice subjected to IR heating. Samples of freshly harvested medium grain rice (M202 variety) with 20.5% and 23.8% (w.b.) moisture contents were used for this study. They were dried with two different radiation intensities (4685 and 5348 W m-2) and exposure times of 15, 30, 40, 60, 90, and 120 s for each drying bed thickness. The three tested drying bed thicknesses were single layer, 5 mm, and 10 mm. After IR drying, the samples were tempered for 4 h followed by natural cooling. The drying rate, moisture removal, and temperature of the rice were determined. The rice temperatures after the IR heating were in the range of 35.9°C to 71.4°C. The heating and drying rates decreased with the increase of bed thickness. Up to 2.2% of moisture was removed during natural cooling after tempering, without additional energy input. IR heating under tested conditions did not have adverse effects on rice sensory and milling quality, including total rice yield, head rice yield, and degree of milling of the dried rice. We concluded that a high heating rate, fast drying, and good rice quality can be achieved by IR heating of rough rice to about 60°C followed by tempering and natural cooling with a tested bed thickness up to 10 mm.

DRYING CHARACTERISTICS AND QUALITY OF ROUGH RICE UNDER INFRARED RADIATION HEATING

Infrared (IR) radiation heating could provide high heating rate and rapid moisture removal for rough rice drying. The objective of this research was to investigate the effect of drying bed thickness on drying characteristics and quality of rough rice under IR heating. The samples of freshly harvested medium grain rice (M202 variety) with 20.5 % and 23.8% (wb) moisture contents were used for this study. They were dried with two different radiation intensities, 4685 and 5348 W/m2, for six exposure times, 15, 30, 40, 60, 90 and 120 s, for each drying bed thickness. The tested three drying bed thicknesses were single layer, 5 mm and 10 mm. After IR drying, the samples were tempered for 4 hours followed by slow cooling. The drying rate, moisture removal and temperature of rice during drying were measured and calculated. The rice temperatures after the IR heating were in the range of 35.9 to 71.4 oC. The heating and drying rates decreased with the increase of bed thickness. A significant amount of moisture was removed during slow cooling after tempering, without additional energy input. The quality of milled rice, including total rice yield, head rice yield, and degree of milling of the dried rice was evaluated. It was concluded that a high heating rate, fast drying and good rice quality could be achieved by heating rough rice to about 60 oC followed by tempering and slow cooling with a bed thickness up to 10 mm.

Effective Disinfection of Rough Rice Using Infrared Radiation Heating

The objective of this study was to investigate the effect of infrared (IR) heating and tempering treatments on disinfection of Aspergillus flavus in freshly harvested rough rice and storage rice. Rice samples with initial moisture contents (IMCs) of 14.1 to 27.0% (wet basis) were infected with A. flavus spores before the tests. The infected samples were heated by IR radiation to 60°C in less than 1 min, and then samples were tempered at 60°C for 5, 10, 20, 30, 60, or 120 min. High heating rates and corresponding high levels of moisture removal were achieved using IR heating. The highest total moisture removal was 5.3% for the fresh rice with an IMC of 27.0% after IR heating and then 120 min of tempering. IR heating followed by tempering for 120 min resulted in 2.5- and 8.3-log reductions of A. flavus spores in rough rice with the lowest and highest IMCs, respectively. To study the effect on disinfection of rewetting dried storage rice, the surface of the dry rice was rewetted to achieve IMCs of 14.7 to 19.4% (wet basis). The rewetting process for the dry rice had a significant effect on disinfection. IR heating followed by tempering for 60 min resulted in 7.2-log reductions in A. flavus on rewetted rough rice. The log-linear plus tail model was applied to estimate the tempering time needed to achieve a 5-log reduction of A. flavus in rice of different IMCs. At least 30 and 20 min of tempering were needed for fresh rice and rewetted rice, respectively, with the highest IMCs. The recommended conditions of simultaneous disinfection and drying for fresh rice was IR heating to 60°C followed by tempering for 120 min and natural cooling, resulting in a final MC of 16.5 to 22.0%, depending on the IMC. For the rewetted dry rice with an IMC of 19.4%, the recommended condition for disinfection and drying involved only 20 min of tempering. The final MC of the sample was 13.8%, which is a safe MC for storage rice.

Effect of Infrared and Conventional Drying Methods on Physicochemical Characteristics of Stored White Rice

The objective of this study was to investigate the effect of infrared (IR) drying followed by tempering and natural cooling on the change of physicochemical characteristics of white rice during up to 10 months of storage. The physicochemical characteristics of IR-dried rice were also compared with those of conventionally dried rice. It took only 58 s to heat the rough rice from room temperature to 60°C with IR, and 2.17 percentage points of moisture was removed. After four months of storage, the increases in yellowness index, water uptake ratio, and volume expansion ratio of the rice dried with IR were 73.8, 63.9, and 55.3% those of rice dried with an ambient air drying method, respectively. IR drying slightly decreased the gelatinization temperature, enthalpy, and viscosities, reduced the changes in microstructure, and maintained cooking characteristics during storage. Therefore, the IR drying process is recommended to maintain the quality of white rice during storage.

Simultaneous decontamination and drying of rough rice using combined pulsed light and holding treatment

BACKGROUND Pulsed light (PL) technology has been proven effective in food disinfection. However, increasing the light intensity or treatment time could swiftly increase the temperature of the food product. Using the thermal effect in an appropriate way may achieve a simultaneous disinfection and drying effect. The objective of this study was to investigate the feasibility of simultaneous disinfection and drying of rough rice using PL and holding treatment. RESULTS Freshly harvested rice samples were inoculated by Aspergillus flavus (A. flavus) and treated using PL under different intensities and durations followed by holding treatment. The PL treatment under intensity of 1.08 W cm(-2) for 21 s led to a reduction of 0.29 log cfu g(-1) on the population size of A. flavus spores. After holding treatment, a 5.2 log cfu g(-1) reduction was achieved. The corresponding total moisture removal reached 3.3% points. No adverse effect on milling quality was detected after the treatment. CONCLUSION The obtained results revealed that the combined PL and holding treatment had good potential for successful application in the rice industry to simultaneously achieve disinfection and drying.

Size and Moisture Distribution Characteristics of Walnuts and Their Components

The objective of this study was to determine the size characteristics and moisture content (MC) distributions of individual walnuts and their components, including hulls, shells, and kernels under different harvest conditions. Measurements were carried out for three walnut varieties, Tulare, Howard, and Chandler cultivated in California, USA. The samples for each variety were collected from the harvester at the first and second harvest of nuts treated with and without ethephon. The nuts were sorted into two categories as with hulls and without hulls before conducting dimension and MC measurements. The results showed that there was a wide range of size distribution for nuts with and without hulls and a huge variability in moisture content among individual nuts at harvest. The average MC of nuts with hulls was much higher than that of nuts without hulls for all tested varieties. The nuts with hulls had an average moisture content of 32.99% compared to 13.86% for nuts without hulls. Also, the shell moisture content was much higher than kernel moisture content. On average, the differences in moisture content between shell and kernel was 11.56% for nuts with hulls and 6.45% for nuts without hulls. There was no significant deference in hull MC between the first and second harvest for the studied varieties. Based on the regression analysis, it was observed that strong relationships exist between the MC of shells and kernels. The obtained results provide information for designing and developing new handling and processing equipments, especially for increased drying capacity, reduced energy use, and obtaining high-quality walnut products.

Determination of Dockage for Accurate Rough Rice Quality Assessment

Abstract. Determination of dockage of freshly harvested rice is crucial for precise development of a universal rice shrink chart. The objectives of this research were to determine the effect of different factors, including rice variety, farm location, harvest moisture and time, drying, dropping, weather events such as wind and rainfall, and type of harvester, on dockage. The study was conducted during two consecutive rice harvesting seasons. The dockage of freshly harvested rice with moisture content (MC) ranging from 18% to 27% wet basis (w.b.) varied between 0.2% and 2.0% with averages of 0.92% and 0.79% in 2010 and 2011 harvest seasons, respectively. The corresponding averages of dockage of dried rice with MC of 14±1% (w.b.) were 0.78% and 0.65%, which were lower than those of freshly harvested rice. There were no significant differences (p>0.05) in dockage among the studied rice varieties. It was also observed that dockage was not significantly affected (p>0.05) by the harvest MC, geographical location and dropping from certain height. However, wind and rainfall events significantly (p

Drying Rates of Thin Layer Rough Rice Drying Using Infrared Radiation

Rice drying with infrared radiation has been investigated during recent years and showed promising potential with improved quality and energy efficiency. However, due to limited penetration capability of infrared radiation, thin layer drying may be used in infrared dryer design. The objective of this study was to study the moisture removal characteristics of thin layer rough rice heated by infrared radiation and cooled with various methods, including natural cooling, forced air cooling and vacuum cooling. The rewetted rough rice samples with four different moisture contents, 16.7, 20.5, 23.6 and 25.7 % (wb), were dried with four different radiation intensities, 3616, 4023, 4685, and 5348 W/m2, for four exposure times, 30, 60, 90, and120 s. The achieved grain temperatures ranged from 35.1oC to 68.4oC under the tested heating conditions. The vacuum and forced air cooling methods had more moisture removal than the natural cooling. The total moisture removal reached to 3.2, 3.5, and 3.8 percentage points for the rice heated to the temperature of 63.5 oC achieved with the infrared intensity of 5348 W/m2 and heating time of 120 s and followed by the natural cooling for 40 min, forced air cooling for 5 min and vacuum cooling for 10 min, respectively. It was concluded that infrared radiation thin layer drying of rough rice followed by cooling could be an effective approach to design infrared rice dryer for improving the drying rates and reducing energy consumption.

Influence of infrared drying on storage characteristics of brown rice

The aim of this study was to improve storage characteristics of brown rice by using infrared radiation drying (IRD) through comparison with hot air drying (HAD) and ambient air drying (AAD). After heating by IR from 20 °C to 60 °C within 58 s, 2.17 percentage points moisture of rough rice (initial moisture content is 25.0 ± 0.2% in dry basis) were removed without adverse effect on germination capacity of husked brown rice. Compared with AAD, IRD slowed down the increase in yellowness, water uptake and volume expansion ratio of brown rice by 47.9%, 41.0% and 37.9% after four months of storage, and decreased the temperature range and enthalpy of gelatinization, the peak and breakdown viscosities. These changes might due to the higher stabilization effect of IRD on the microstructure and thermal properties of proteins and starch granules than AAD. IRD is an effective method to improve storage stability of brown rice.

Simultaneous Rough Rice Drying and Disinfestation Using Infrared Radiation

The objective of this study was to investigate the drying characteristics, milling quality, and disinfestation effectiveness of rough rice under infrared (IR) radiation heating. Freshly harvested medium grain rice (M202) samples with low (20.6%) and high (25.0%) moisture contents (MC) were used for this study. Single-layer rough rice samples (non-infested and infested with the adults and eggs of lesser grain borers (Rhizopertha dominica) and angoumois grain moths (Sitotroga cerealella) were heated for various durations using a catalytic infrared emitter. The effects of tempering treatment and natural and forced air cooling methods on moisture removal, milling quality and disinfestation were also determined. High heating rate and corresponding high moisture removal were achieved by using the IR heating. After heating, tempering increased moisture removal during cooling and improved milling quality of the rice samples. For example, 60 s of IR heating of 20.6% MC rice resulted in 61.2°C rice temperature, 1.7 percentage MC removal during the heating period and additional 1.4% MC removal after tempering and natural cooling. The rice also had 1.9 percentage higher head rice yield than control sample dried with room air. The heating and tempering treatment also completely killed the tested insects. However, rice samples without tempering or cooled with forced air after tempering had much lower milling quality than the control. Simultaneous drying and disinfestation with high rice milling quality can be achieved by using the catalytic IR to heat the rough rice to 60°C followed by tempering and slow cooling.