Impacts of Specific Power of Microwave at 915 MHz Frequency on Drying and Milling Characteristics of Parboiled Rough Rice

2021 ◽  
Vol 37 (2) ◽  
pp. 359-366
Author(s):  
Deandrae Lynette Smith ◽  
Griffiths G. Atungulu
Keyword(s):  
Rice Yield ◽  
Least Square ◽  
Specific Power ◽  
Drying Rate ◽  
Milled Rice ◽  
Volumetric Heating ◽  
Parboiled Rice ◽  
Rough Rice ◽  
Milling Characteristics ◽  
Drying Rates

HighlightsThis research investigated the feasibility of using a microwave (MW) set at 915 MHz frequency to dry high moisture content (MC) parboiled rough rice at 44.3% MC dry basis (d.b.).The research evaluated the impacts of specific power delivered during the drying of parboiled rough rice using a MW on post-drying milling characteristics.The volumetric heating phenomenon provided by MW offered a method to quickly remove 23.1% points of moisture from parboiled rough rice in one-pass to a MC of 21.2% d.b., with minimal impacts on the kernel quality.The findings suggest that increased MW specific powers have a positive effect on rice MC reduction but negatively affects the rice milling characteristics, especially the head rice yield.The study recommended that MW specific powers exceeding 2.92 kW.[kg-DM]-1 should not be exceeded during drying of parboiled rough rice to preserve the rice milling yields.ABSTRACT. The objectives of this research were to study the impacts of specific power of MW generated at 915 MHz frequency to dry high MC parboiled rough rice on moisture removal and milling characteristics of the parboiled rough rice. Long-grain rough rice of the cultivar (cv.) Mermentau at harvest MC of 31.6% dry basis (d.b.) was parboiled by soaking at 73°C for 3 h and then steamed at 67 kPa for 10 minutes. Following the parboiling process the sample was subjected to the MW drying. The drying was accomplished at MW specific powers that ranged from 1.10 to 8.77 kW. [kg-DM] -1 and 0.37 to 2.92 kW. [kg-DM] -1 (power per unit dry matter mass of the grain). These treatment levels of MW specific power were varied by heating parboiled rough rice for 2 and 6 minutes (min) at MW powers that ranged from 1 to 24 kW. The process of parboiling increased the rough rice MC to 44.3% dry basis (d.b.). During the MW drying, as the specific power increased, the general tendency was for rough rice final moisture content (FMC), milled rice yield (MRY) and head rice yield (HRY) to decrease while the drying rate increased. Parboiled rough rice samples treated with a specific power of 8.77 kW.[kg-DM] -1 while maintaining specific energy input at 0.29 kWh.[kg-DM] -1 had least-square means FMC, drying rate, MRY and HRY of 19.7% d.b. (S.D ± 1.1%), 12.3% d.b. [min-1] (S.D ± 0.8%) (2 min drying duration), 68.18% (S.D ± 1.70%) and 67.51% (S.D ± 0.73%) respectively. However, treatment at a lower specific power of 2.92 kW.[kg-DM] -1 while maintaining the same specific energy input of 0.29 kWh.[kg-DM]-1) resulted in least-square means FMC, drying rate, MRY and HRY of 21.2% d.b. (S.D ± 0.5%), 3.9% d.b. [min-1] (S.D ± 0.1%) (2 min drying duration), 73.22% (S.D ± 0.84%) and 73.21% (S.D ± 0.21%) respectively. The increased drying rates for treatments with higher specific power was associated with higher treatment powers and shorter treatment durations. Higher specific powers negatively impacted the observed MRY and HRY. The findings suggest that increased MW specific powers have a positive effect on rice MC reduction but above a certain threshold of specific power (2.92 kW.[kg-DM]-1) may negatively affect the milling characteristics of the parboiled rice. When used to dry high MC parboiled rough rice, rice processors should know that there exists an optimum drying rate that if exceeded the milled rice quality is negatively affected thus generating an economic loss to the parboiled rice industry. The volumetric heating phenomenon provided by microwave (MW) offers a means to quickly dry high MC parboiled rough rice. This can translate to considerable economic savings for the rice processor who often experiences low drying rates because of limited drying capacity, especially at peak rice harvest times. When drying rates are optimized, rice processors can expect minimal impacts on the kernel quality which can also be translated to considerable economic savings for the rice processor. Keywords: 915 MHz microwave, Microwave drying, Milling Quality, Parboiled rice, Specific power.

Effect of Storage Moisture Content on Milling Characteristics of Rough Rice

2019 ◽  
Vol 62 (4) ◽  
pp. 1011-1019
Author(s):  
Bhagwati Prakash ◽  
Terry J. Siebenmorgen ◽  
Kristen E. Gibson ◽  
Shweta Kumari
Keyword(s):  
Moisture Content ◽  
Rice Yield ◽  
Surface Lipid ◽  
Milled Rice ◽  
Financial Return ◽  
Head Rice ◽  
Rough Rice ◽  
Head Rice Yield ◽  
Milling Characteristics ◽  
The Mean

Abstract. Rough rice in the Mid-South U.S. is typically stored and milled at a moisture content (MC) between 12% and 13% on a wet basis. Drying harvested rice to lesser MCs requires increasingly greater energy and reduces the overall mass of rice, both of which translate into lesser financial return for the crop. Considering these disadvantages of drying and storing rice at lesser MCs, farmers and grain handlers have been interested in exploring storing rice at slightly greater MCs. The current study was undertaken to evaluate the effect of storing rice at five MCs (11%, 12%, 13%, 14%, and 15%) on milling characteristics, particularly surface lipid content (SLC), milled rice yield (MRY), and head rice yield (HRY); additionally, the effects of storing rice at two storage temperatures (25°C and 35°C) and several storage durations (up to one year) on milling characteristics were investigated. Five long-grain rice lots were harvested in 2016 and 2017 from several locations in Arkansas; rice from each lot was gently dried to the target MCs and then stored in sealed glass jars at selected temperatures. With an increase in storage MC, shorter milling durations were needed to achieve a given SLC, which could potentially reduce the cost of the milling operation. However, rice samples stored at greater MCs were observed to have lesser HRYs, which could reduce the economic value of rice. The mean HRYs of the 15% MC samples were 4.8 to 9.1 percentage points less than the mean HRYs of the 12% MC samples. This study quantifies the milling characteristics of rice when stored for various durations at different MCs and temperatures. Overall, these data will allow the rice industry to make informed decisions related to storage conditions of rice, specifically storage MC. Keywords: Head rice yield, Milling, Moisture content, Rice, Storage.

X-Ray Detection of Fissures in Rough Rice Kernels

2017 ◽  
Vol 33 (5) ◽  
pp. 721-728 ◽  
Author(s):  
Zephania R. Odek ◽  
Bhagwati Prakash ◽  
Terry J. Siebenmorgen
Keyword(s):  
Rice Yield ◽  
X Rays ◽  
Milled Rice ◽  
Substantial Impact ◽  
X Ray ◽  
X Ray Imaging ◽  
Head Rice ◽  
Rough Rice ◽  
Head Rice Yield ◽  
Rice Drying

Abstract. X-ray imaging is a viable method of fissure detection in rough rice kernels owing to the ability of X-rays to penetrate hulls, thus allowing visualization of internal rice kernel structure. Traditional methods of fissure detection are only applicable for brown and milled rice, and therefore cannot be used to study fissures developed during rough rice drying. In this study, the fissure detection capability of an X-ray system was evaluated and the relationship between head rice yield (HRY), as measured through laboratory milling, and the percentage of fissured rough rice kernels was determined. Long-grain rice lots of various cultivars were dried using heated air at 60°C, 10% relative humidity (RH) for five drying durations to produce different degrees of fissuring, and then milled to determine HRY. A strong linear correlation (R2 = 0.95) between HRY and the percentage of fissured rough rice kernels after drying was determined. This correlation confirms the substantial impact that kernel fissures have on milling yields. Overall, these findings show the effectiveness of X-ray imaging in rough rice fissure detection, which could allow for drying research that may provide a better understanding of kernel fissuring kinetics. Keywords: Fissures, Grainscope, Head rice yield, Rice drying, X-ray imaging.

Prediction of Rice Milling Yield and Quality Attributes during Storage Using Regression Analyses

2019 ◽  
Vol 62 (5) ◽  
pp. 1259-1268
Author(s):  
Soraya Shafiekhani ◽  
Jung Ae Lee ◽  
Griffiths G. Atungulu
Keyword(s):  
Hybrid Rice ◽  
Storage Temperature ◽  
Rice Yield ◽  
Storage Conditions ◽  
Milled Rice ◽  
Yield And Quality ◽  
Head Rice ◽  
Rough Rice ◽  
Milling Yield

Abstract. Regression analyses were performed to determine the storage conditions that exhibited the best outcomes for long-grain, hybrid milled rice yield and quality. This study evaluated mold population on rough rice, milled rice discoloration, and head rice yield (HRY) after storage of rough rice in airtight conditions at moisture contents (MCs) of 12.5%, 16%, 19%, and 21% wet basis and temperatures of 10°C, 15°C, 20°C, 27°C, and 40°C at two-week intervals for 12 weeks. The experiment used a popular long-grain hybrid rice cultivar (XL745). Rice lots were procured from fields with and without conventional treatment of the field with fungicide for plant disease management. Field treatment and no field treatment were considered as a block, and a Mann-Whitney test was conducted to determine effect. The response surface method, an extension of second-order polynomial regression, was used to examine optimal treatment conditions. Mold population and milled rice discoloration from a combination of storage conditions were predicted using regression models. The first-order and second-order terms of temperature indicated a nonlinear relationship between temperature and ln(discoloration). The MC was positively associated with ln(discoloration), but the degree of impact may change with temperature because the interaction term was significant. From the model evaluation (R2 and lack-of-fit test), the discoloration level is expected to be 57% (49% to 66% confidence interval) under conditions of 20% MC, 40°C, and nine weeks of storage for samples procured from fungicide-treated rice fields. This discoloration change is substantial compared to the initial discoloration of 9%. At high temperature (40°C) and MC (21%), discoloration started immediately after two weeks of storage. Anaerobic storage conditions impeded mold growth, especially at high storage temperature (40°C). Low mold populations were observed in rice stored at low MC (16%). According to the regression model, the critical storage temperature that may lead to discoloration is between 27°C and 40°C. Pre-harvest fungicide treatment of rice in the field for disease control significantly improved the HRY but had no significant influence on mold population or discoloration. This study suggests a range of storage conditions to prevent losses in milling yield and quality of rice. In addition, the studied storage conditions mimicked the typical conditions for on-farm, in-bin drying and storage in the U.S. Mid-South, especially for the top layers of rice inside the bin, and therefore provide an important reference for growers and rice processors using in-bin structures to manage the quality of long-grain hybrid rice. Keywords: Discoloration, Head rice yield, Mold population, Regression analysis, Rice quality, Rice storage.

Effect of Rice Chilling on Drying, Milling, and Quality Characteristics

2020 ◽  
Vol 36 (5) ◽  
pp. 767-776
Author(s):  
Soraya Shafiekhani ◽  
Griffiths G Atungulu
Keyword(s):  
High Temperature ◽  
Cold Storage ◽  
Storage Temperature ◽  
Rice Yield ◽  
Quality Characteristics ◽  
List Type ◽  
Milled Rice ◽  
Heated Air ◽  
Rough Rice

HighlightsThis study experimentally simulated drying of rough rice subjected to various cold storage/chilling conditions.The rice was dried using slightly-heated air and high temperature air with procedures set to mimic those practiced by commercial systems.The moisture removal, drying rate constant, material state transition, milling and quality characteristics of rice upon drying conditions was investigated.The study provides important reference information for growers and rice processors using the relatively new rice cooling technology.Abstract. High temperature (field heat) and moisture content of freshly harvested rough rice promote excessive respiration and microbial growth. Therefore, the rice risks significant deterioration of quality due to delayed drying at peak harvest time when drying capacity becomes limited. The U.S. rice industry has identified that cooling/chilling the rice prior to drying to remove the excess heat, immediately after harvest, significantly preserves the quality of milled rice. This study experimentally simulated drying of rough rice after cold storage/chilling. The rice was dried using slightly-heated air and high temperature air with procedures set to mimic those practiced by commercial systems. Rough rice at moisture contents (MCs) of 16%, 19%, and 21% (wet basis) were stored at storage temperature (Ts) of 10°C, 15°C, and 20°C for up to 4 months. Following retrieval, the samples were dried at drying temperature (Td) of 35°C, 45°C, and 60°C and relative humidity (RH) of 20%. Each drying run comprised of two 20-min drying passes with the rice tempered at the drying Td for a duration of 4 h following every drying pass. Following the drying, the rice was conditioned in an equilibrium MC chamber (T=26°C, RH=56%) to 12.5% MC and then milled to evaluate milled rice yield and quality characteristics. The highest percentage points of MC removal (6.77% points) occurred following drying at air temperature of 60°C for samples with initial MC at 21% and stored at 20°C. Drying with air at 60°C decreased head rice yield (HRY) especially for samples with initial MC at 21% and stored at 10°C (HRY=51.4% versus those at 45°C and 35°C, HRY=55.95% and HRY=58.8%, respectively). Drying air temperatures studied (35°C, 45°C, 60°C) had no significant effect of causing discoloration of samples within the range of the studied initial MCs and storage temperatures. Peak and final viscosities of samples with different initial MCs (16%, 19%, and 21%) stored at 20°C followed by high temperature air drying (60°C) were significantly different from those of samples stored at 10°C and 15°C. The results provided insight into the drying, milling, and quality characteristics of rice after cold storage/chilling. The information provide foundation for development of new recommendations to improve quality of milled rice. Keywords: Conventional drying, Cooling/chilling, Milling quality, Rough rice, Storage.

Milled Rice Quality Assessment

2010 ◽  
Vol 6 (2) ◽  
Author(s):  
Reza Farahmandfar ◽  
Esfandiyar Farahmandfar ◽  
Mahdi Ghasemi Varnamkhasti ◽  
Mahdi Zarei
Keyword(s):  
Rice Yield ◽  
Milling Process ◽  
Milled Rice ◽  
Rice Varieties ◽  
Breeding Lines ◽  
Head Rice ◽  
Rough Rice ◽  
Degree Of Milling ◽  
Head Rice Yield ◽  
Important Processing

Milling, an important processing step of rough rice, is usually done to produce white, polished grains. In this paper the quality of 22 milled rice varieties, common in Mazandaran, Iran, are investigated. These rice varieties included local varieties and breeding lines. Parameters assessed were head rice yield, degree of milling, husk removed percent, and total milling recovery. Results obtained revealed that the Tarom Mahali and Champa varieties have the highest head rice yield as 60.58 and 66.39 % and total milling recovery as 69.96 and 71.38 %, respectively. The greatest degree of milling value was found for the Haraz variety with a mean of 16.06 %. Also, it was found that the husk removed percent values were not statistically different among the varieties studied. Finally, considering all results obtained, the varieties of Tarom Mahali, Champa, and Neda showed to be more economical in the milling process.

Drying of Rough Rice Using Heated Husk for Heat Transfer and Moisture Adsorption

2018 ◽  
Vol 34 (3) ◽  
pp. 605-615 ◽  
Author(s):  
Sammy S. Sadaka ◽  
Griffiths G. Atungulu
Keyword(s):  
Heat Transfer ◽  
Moisture Content ◽  
Rice Husk ◽  
Rice Yield ◽  
Ambient Air ◽  
Coefficient Of Determination ◽  
Drying Rate ◽  
Air Drying ◽  
Rough Rice ◽  
Rice Samples

Abstract. Drying of small size samples usually represents a challenge to rice researchers. Using natural air drying to dry these samples exposes them to the fluctuations of ambient air conditions. Therefore, the goal of this research was to evaluate the suitability of drying small size rough rice samples using heated husk as a heat transfer and moisture adsorbent medium. The proposed drying technique could be an attainable process, particularly because it represents conduction heat and moisture transfer rather than natural air drying. The required amounts of rice husk were placed in aluminum containers and kept in an oven overnight to reach the desired temperature. Heated husk samples were mixed with rough rice and maintained for the desired drying duration; following which, the husk and rough rice mixtures were separated pneumatically. The separated rough rice samples were collected to determine moisture content, drying rate, and rice quality. The highest mixture temperature of 34.0°C was achieved at the highest husk to rough rice ratio of 1:2 and the highest husk temperature of 110°C after 4 minutes. A maximum of 6.4% moisture reduction points was achieved by mixing the rice husk to rough rice by 1:2 on a weight basis and employing heated rice husk at 100°C. The highest drying rate of 5.99%/h was achieved during the first hour of drying with the husk-to-rough rice ratio of 1:2 and the husk temperature of 100°C. Milled rice yield ranged between 63.4% and 72.0% while the head rice yield ranged between 39.9% and 67.9%. An empirical correlation was developed to calculate the normalized moisture content as a function of the husk to rough rice ratio, the husk temperature and drying duration with a coefficient of determination of 0.775 under the studied conditions. Keywords: Conduction drying, Heat transfer medium, Moisture absorbent, Rice husk, Rough rice.

Processing Parameters for One-Pass Drying of High-Moisture Parboiled Rough Rice with 915 MHz Microwaves

2021 ◽  
Vol 64 (1) ◽  
pp. 299-312
Author(s):  
Deandrae L. Smith ◽  
Griffiths G. Atungulu ◽  
Andy Mauromoustakos
Keyword(s):  
Moisture Content ◽  
Protein Content ◽  
Specific Energy ◽  
Rice Yield ◽  
Microwave Drying ◽  
High Moisture ◽  
Milled Rice ◽  
Physiochemical Properties ◽  
Rough Rice ◽  
C 73

HighlightsThe impact of parboiling process parameters on the feasibility of one-pass microwave drying of high-moisture parboiled rough rice was investigated.Rough rice was parboiled by 3 hours of soaking in water at 71°C, 73°C, or 76°C and then steamed for 5, 10, or 15 min prior to microwave drying at 915 MHz.Moisture content following parboiling at the studied conditions ranged from 42.59% to 48.21% dry basis.Microwave specific energies ranging from 0.04 to 0.29 kWh per kg of parboiled rough rice dry matter (kWh kg-DM-1) were used to dry the parboiled rough rice.Soaking at 73°C and steaming for 10 min followed by one-pass microwave drying at 0.29 kWh kg-DM-1 gave the best results in terms of parboiled rough rice final moisture content and post-drying milling and physiochemical properties.Microwave treatment can provide one-pass drying of parboiled rough rice.Abstract. The volumetric heating phenomenon of microwaves (MW) offers a means to quickly dry high moisture content (MC) parboiled rough rice in one pass. However, to successfully dry parboiled rough rice in one pass using MW while preserving the milled rice yield and quality characteristics, it is vital to investigate the impacts of the pre-drying parboiling conditions on the drying process and the resulting product characteristics. The objectives of this study were to explore the feasibility of using MW at 915 MHz to dry high-MC parboiled rough rice and to determine the implications of the pre-drying soaking and steaming conditions on the parboiled rough rice final moisture content (FMC), milled rice yield (MRY), head rice yield (HRY), and the milled rice physiochemical properties. Freshly harvested, long-grain rough rice of the cultivar Mermentau at MC of 31.58% dry basis (d.b.) was used in this study. The parboiling process involved soaking the rough rice in water at temperatures of 71°C, 73°C, or 76°C and steaming for 5, 10, or 15 min. After parboiling, samples of rough rice for the controlled experiment were gently dried with natural air at 25°C and 65% relative humidity, while samples for MW treatment were dried using a 915 MHz MW dryer, which was set to deliver energy ranging from 0.04 to 0.29 kWh per kg of rough rice dry matter content (kWh kg-DM-1). The MW power applied during treatment ranged from 1 to 8 kW with heating durations of up to 6 min. The rough rice MC immediately increased after the soaking and steaming processes and ranged from 42.59% to 48.21% d.b. Increased soaking temperature led to increased uptake of water after parboiling, decreases in MRY, HRY, protein content, and milled rice surface lipid content (SLC), and increases in total color difference (TCD). Increased steaming duration led to decreased moisture uptake during steaming, decreased MRY, protein content, SLC, and TCD, and increased HRY. Increased MW specific energy led to decreased FMC, HRY, protein content, and SLC and increased TCD. It is recommended that long-grain rough rice should be soaked at 73°C, steamed for 10 min, and then treated at MW specific energy of 0.29 kWh kg-DM-1 in one pass to achieve parboiled rough rice FMC of 18.79% d.b., HRY of 69.33%, and desirable parboiled milled rice physicochemical and sensory properties. At the same parboiling conditions, the control samples had MRY of 74.98% and HRY of 74.07%. MW specific energy greater than 0.29 kWh kg-DM-1 was necessary to dry the parboiled rough rice to MC safe for long-term storage (14.29% to 15.61% d.b.). However, the application of specific energy beyond 0.29 kWh kg-DM-1 caused a reduction of HRY below that of the control samples. Therefore, to preserve HRY, rice processors should use MW specific energy of 0.29 kWh kg-DM-1 to partially dry parboiled rice and then complete the drying to a safe storage MC by using natural or slightly heated air. This study demonstrates the feasibility of using 915 MHz MW heating of high-MC parboiled rough rice to achieve one-pass drying. Keywords: 915 MHz microwaves, Milling yields, One-pass drying, Parboiled rough rice, Physicochemical properties, Rice quality.

Sign in / Sign up

Export Citation Format

Share Document