Quality Of Parboiled Rice Research Articles

Ohmic heating using electrolytes for paddy parboiling: A study on thermal profile, electrical conductivity, milling quality, and nutritional attributes

AbstractOhmic heating (OH), a novel thermal technique could be utilized for paddy parboiling to improve milled rice quality. In this research, two paddy varieties (one traditional and one modern variety) were subjected to OH at different salt concentrations (0%, 0.3%, 0.5%, 0.7%, and 0.9%) and voltage gradients (10, 12, 14, 16, and 18 V/cm) and their influence on thermal profile, electrical conductivity (EC), milled rice quality, and nutritional profile were studied in comparison to the conventional steaming method. A factorial design was used to determine the effect of variety, voltage gradient and holding time on head rice yield (HRY), hardness and color difference of parboiled milled rice. Results indicated the significance of salt and voltage on processing time and HRY. On increasing, both enhanced the EC and heating rate leading to a great reduction in parboiling duration whereas HRY increased on lowering the voltage. High significant effects were observed between the factors for HRY and color. The maximum HRY and hardness were obtained for OH at 0.7% salt and 12 V/cm. This treatment when compared to steaming, consumed less energy, and provided less chalkiness, better HRY and hardness for both varieties to a greater extent. OH also positively impacted the nutritional profile of parboiled rice as it retained more protein and fat than the conventional method. These results reveal the superiority of OH in providing a significant favorable impact on the parboiled milled rice quality and has a great potential to be used for paddy parboiling.Practical applicationsOhmic heating is an emerging thermal technique having the potential for rapid uniform heating. In this study, OH was utilized for paddy parboiling by incorporating electrolytes for replacing the conventional steaming method. Steaming requires a boiler for generating steam, which adds to the processing cost and equipping OH eliminates the need for a boiler. This will save water, energy, space, manpower, and maintenance requirements. OH also reduces the parboiling duration, while improving parboiled rice quality. The ohmic behavior of paddy will also facilitate the design of continuous ohmic systems for paddy parboiling which can be immensely useful in the rice processing industry.

Multiobjective optimization of parboiled rice quality attributes and total energy consumption

This study was designed to investigate, model and optimize the effect of process factors (soaking temperature, soaking time, steaming time and paddy moisture content) on rice quality attributes and total energy consumption of a commercially grown rice variety (FARO 60) using response surface methodology. The optimum processing conditions obtained for the rice quality attributes and total energy consumption varies from one another. The milling recovery, head rice yield, white bellies, lightness, colour, and total energy consumption values of the parboiled rice ranges from 68.46 - 72.34%; 67.71 - 71.42%; 0.50 - 4.30%; 22.03 - 33.00; 14.10 - 21.21 and 45.27 - 73.68 MJ, respectively. The second-order polynomial models were observed to be fit in predicting milling recovery, head rice yield, white bellies and total energy consumption with the coefficient of determination (R2) that range from 78.71 to 95.03% while colour and lightness values were not fit with R2 ranging from 24.05 to 52.95%. The multiobjective optimization for desirable parboiled rice quality attributes and total energy consumption showed that universal optimum condition was found at 64°C soaking temperature, 11 h soaking time, 35 min steaming time and 17% paddy moisture content. The approach used and information obtained from this study would be useful for rice processors as a strategic means of minimizing total energy consumption, without compromising its desirable quality attributes.
 Keywords: Multiobjective Optimization; Parboiled Rice Quality Attributes; Total Energy Consumption

Effects of operating parameters of impinging stream dryer on parboiled rice quality and energy consumption

It is very important to know how operating condition of a coaxial impinging stream dryer affects the drying time, parboiled rice quality and energy consumption. The drying temperature, parboiled paddy feed rate, drying air velocity and impinging distance were experimentally investigated. Increases in drying temperature and air velocity and a decrease in paddy feed rate provided higher evaporation rate whilst impinging distance, ranging from 5 to 13 cm, did not affect the evaporation rate. Collision between kernels within the impinging zone caused the hull’s lemma splitting from the kernel and the percentage of the split kernel strongly depended on the air velocity and feed rate. The acceleration in the rate of drying by changing the above operating parameters did not affect the head rice yield. In addition, the collision of kernels also did not influence the head rice yield since the mechanical properties of rice are strengthened during steaming step in the parboiling process. However, the change of head rice quality was only governed by the moisture content after drying. The total energy consumption including electricity and heat was strongly depended on the air velocity and feed rate whilst it was slightly changed with the drying temperature. From the present study, it was recommended that the parboiled paddy should not be dried below 25% d.b. and the highest temperature that could possibly be used was 190 °C and the inlet air velocity should not be below 15 m/s.

Pengaruh Lama Perendaman Terhadap Mutu Beras Prantanak pada Padi Varietas IR 64

ABSTRAK Pembuatan beras pratanak meliputi pembersihan, perendaman, pengukusan, pengeringan, dan penggilingan. Proses pratanak dimaksudkan untuk meningkatkan rendemen giling, menekan kehilangan nilai gizi dan menurunkan indeks glikemik sehingga cocok dikonsumsi oleh penderita Diabetes Melitus. Tujuan dari penelitian ini adalah (1) Mengkaji pengaruh lama perendaman terhadap mutu fisik dan kimia beras pratanak, (2) Menentukan lama perendaman yang optimum untuk proses pratanak dan pengaruhnya terhadap mutu beras. Penelitian ini menggunakan gabah varietas IR 64 dengan perlakuan lama perendaman 4, 6, dan 8 jam. Hasil penelitian menunjukkan bahwa proses pratanak dapat meningkatan rendemen giling dan dapat menurunkan kadar amilosa. Profil gelatinisasi beras pratanak menunjukkan bahwa semakin lama perendaman dalam proses pratanak dapat meningkatkan viskositas trough, viskositas akhir, waktu puncak, dan suhu gelatinisasi serta menurunkan viskositas puncak, viskositas breakdown, dan viskositas setback. Lama perendaman tidak berpengaruh secara signifikan terhadap komposisi kimia yang terkandung dalam beras pratanak. Lama perendaman yang terbaik adalah selama 4 jam pada suhu air 60 oC. Kata kunci: gabah, beras pratanak, indeks glikemik, amilosa, profil gelatinisasi ABSTRACT Processing of parboiled rice consists of paddy cleaning, soaking, steaming, drying, and milling. Parboiled process of paddy is intended to increase the milling yield, to prevent nutrition losses and to decrease glychemic index. The purpose of this research is (1) To assess the impact of soaking time on the physical and chemical quality of parboiling rice, (2) To determine the optimum soaking time for parboiling rice and it’s impact on rice quality. This research is using IR 64 variant with soaking duration treatment about 4, 6, and 8 hours. The result showed that parboiled process increase the milling yield and reduce the rice amylose content. Gelatinization profile of the parboiled rice showed that the longer of soaking duration increase the trough viscosity, final viscosity, peak time viscosity, and pasting temperatures and also decreased the peak viscosity, breakdown viscosity, and setback viscosity. The treatment of soaking duration did not significantly affect the chemical contents of parboiled rice. The exposure time of paddy soaking that suggested is 4 hours in dip water at temperature of 60 oC. Keywords : paddy, parboiled rice, glychemic index, amylose, gelatinization profileDiterima: 10 Desember 2012 ; Disetujui: 28 Maret 2013

Effects of Simultaneous Parboiling and Drying by Infrared Radiation Heating on Parboiled Rice Quality

An infrared (IR) radiation heating and vibrating apparatus was used to study a simultaneous parboiling and drying process. Physicochemical properties such as milling yield, color, and pasting properties of parboiled paddy were evaluated. Radiation intensity levels of 46.7 kW/m2, variable exposure time, and rice samples at fixed initial moisture contents (IMC) of 30 and 32% wet basis (wb) were used. It was discovered that the radiation intensity of 46.7 kW/m2 and 32% wb moisture content yielded a quality level similar to that of conventional steam-parboiled rice. The head rice yield (HRY) of IR paddy slightly decreased with increased exposure time. The HRY of IR heating was more than 60% compared to HRY values of 67.68 to 69.34% for conventional steam-parboiled rice. The b-values of 23 to 25 for IR samples showed lighter yellowness than the 29.7 b-value of conventional steam-parboiled rice. The pasting properties of all IR samples showed lower viscosity compared to the raw-milled rice samples but higher than conventional steam-parboiled rice. Initial moisture content of paddy affected the degree of starch gelatinization (SG) by differential scanning calorimetry (DSC). Under IR heating for 18 min of exposure time, the 32% wb IMC sample showed SG at 80.15% compared to SG at 59.02% with the 30% wb IMC sample. Hence, while employing simultaneous parboiling and drying with IR heating for an exposure time of 18 min, the sample retained more parboiled flavor as a result of a higher degree of starch gelatinization. The sample showed lower HRY, but yellowness was within the acceptable range. Energy requirement for producing 1 ton of parboiled paddy by the IR heating process is lower than the conventional steam-parboiled process but statistically nonsignificant (P > 0.05). However, the process time was reduced to one third of the conventional process, leading to improved quality. In addition, initial investment cost was minimal because a steam generator was not required.

VACUUM PRESSURE INFLUENCE ON WATER UPTAKE AND QUALITY OF RICE GRAIN DURING SOAKING

The soaking time can be reduced by minimizing the effect of air which is trapped in the caryopsis and between it and the husk. This air resists water movement into the kernel. This paper explores the use of a vacuum and then breaking the vacuum when the paddy rice is soaked to reduce volume of the air, for paddy rice (Giza 181). This would reduce the soaking time in cold water and leads to improvement in the quality of parboiled rice. The simple technique is used to be suitable for poor villages in Africa and Asia where there is no electricity and used rice boiled in their own homes. By using the a pump in four levels of absolute vacuum deareation as 400, 600, 800 and 1000 mbar at 30°C the moisture content of paddy rice was determined before soaking and after different times 1, 2, 4, 6 and 12 hours from the beginning of soaking. The results showed that the samples moisture absorption affected by the levels of vacuum, and the sample evacuated at 400 mbar absorbed a few amount of water more than the sample at 1000 mbar. The increasing in moisture gain due to vacuum levels was evaluated. Becker's diffusion equation was used to predict some soaking behavior of paddy; the moisture gain in the grain was noted experimentally and plotted against the square root of the absorption time under different vacuum conditions. Quality tests show that the process of vacuum deareation before soaking improved the parboiled rice quality substantially, breakage varied from 12 to 14 % for raw paddy while for parboiled paddy it varied from 1.6 to 2.1%. Also white bellies decreased from 8.5% to 5.4%, and hardness was increased from 7.8 kg to 9.3 kg when vacuum levels changes from 1000 mbar to 400 mbar.

Quality characteristics of milled and cooked rice affected by hydrothermal treatment

A factorial design was used to determine the effects of hydrothermal process conditions on parboiled rice quality. The effect of temperature, heating time and tempering on head rice yield (HRY), translucence index (TI) and rupture force (RF) of milled grain was investigated. The effect of tempering and cooking time on texture profile analysis (TPA) of cooked parboiled rice was also studied. The quality indexes increased with tempering. A significant effect of heating time on RF and TI indexes was observed, while temperature affected mainly RF and TI quality indexes. The optimum conditions included tempering after soaking (24 h at 25 °C) and heating at 85 °C (174.4 min) or 93.7 °C (45 min). The rice presented intermediate values of textural properties between raw and traditional parboiled rice. It means less hard than traditional parboiled rice and less sticky than raw rice.

Effect of continuous steaming on parboiled rice quality

A prototype model of a continuous flow steamer was designed and developed taking into consideration the flow characteristics of high-moisture rough rice through a pipe. The model consisted of a hopper to hold soaked rough rice, a steaming section and an outlet to remove gelatinized rough rice at controlled rate. Regulation of rough rice exposure to steam was achieved by manipulating the settings of the discharge mechanism. Rough rice soaked at 60 °C for 5 h and equilibrated overnight was steamed using the device. A 10 ° inclination of the discharge flap and discharge port area of 28.9 cm 2 was found to give optimum quality of parboiled rice with steam supplied at a rate of 9 kg/h and pressure of 1.5 kg/cm 2. Under these conditions, the capacity of the steamer was 104.5 kg/h parboiled rice with 14% moisture content (wb). The developed steamer has a capacity of approximately 2.7 times that of conventional steamers with only about one-third of the steam requirement. These results indicate potential applications for reducing the cost of parboiling equipment by precluding the need for large boilers and steaming tanks with elaborate steam distribution systems, in addition to improvements in the quality of the parboiled rice.

Soak Temperature and Equilibrium Effect on Parboiled Rice Quality

The effect of soak water temperature and partial equilibration after soaking on the quality of parboiled rice was investigated. The quality characteristics that were evaluated were kernel breakage from milling, color, deformity, and the percentage of completely gelatinized (translucent) grains. The translucent grains percentage increased with an increase in both soak temperature and period of equilibration after soaking. The deformity of parboiled rice decreased with an increase in the equilibration period. The results for the color and breakage did not show a consistent trend.

Drying and Tempering Effects on Parboiled Rice Quality

ABSTRACT A study of high temperature drying and tempering of parboiled rice was undertaken to evaluate the effects on grain quality. Thirty-six treatments with three levels of air temperature, three levels of moisture (of rice after exposure in the dryer) and four levels of tempering were performed on Saturn variety medium grain rice parboiled under a constant set of conditions. These conditions were: 4 h of soaking at 60C, 4 h of moisture equilibration after soaking and finally heat treatment with steam at 103.5 kPa pressure for 10 min. At the end of the tempering process the samples were moisture equilibrated under room conditions and subjected to standard milling procedures. Analyses were performed to evaluate color and strength characteristics of the milled rice. A time-based study of kernel hardness and strength properties was also performed for 93 h after drying on separate samples for a selected treatment combination. The intermediate air temperature of 93.3C, for any single tempering treatment produced the highest head yield in the rice samples. This trend was sustained over all the moisture levels to which the samples were dried. This trend together with the increase of color and strength properties of the rice kernels was attributed to the extended parboiling effect at this temperature. The tempering treatment TM2, where the rice samples, placed in sealed containers to prevent any exchange of moisture, were gradually brought to room temperature, realized the highest head rice yield especially for the 93.3C air temperature drying treatment. The tempering treatments (TM2 through TM4) devised for this study were beneficial in terms of improvement of nearly 8% in head yield over the control tempering treatment TM1 where the rice samples were allowed to stabilize to room temperature in the open in the laboratory. The time-based study indicated that grain kernel fissures were not present although breakage still occurred in the samples. Comparison of the strength characteristics from the time-based study with those of the main experiment showed that improvement of strength characteristics persisted for several weeks. A delay of approximately three weeks prior to milling was considered appropriate to realize optimum milled rice yields.

Parboiled Rice Quality as Affected by the Level and Distribution of Moisture after the Soaking Process

ABSTRACT A study of the soaking process in rice parboiling was conducted to evaluate the effects of level and distribution of moisture after soaking on grain quality. Saturn variety medium grain rice was subjected to dif-ferent soaking times with and without pressure, steaming times, and periods of partial equilibration after soaking. The parboiled rice was processed and analyzed for yields, translucency and color. Photomicrographic examina-tions were also performed. Grain moisture levels as low as 23.5 percent (wet basis) after soaking were found adequate to obtain high head yields. Pressure soaking considerably reduced soaking times, and the partial equilibration of the grains after the soaking stage was observed to improve the percent whole grain, grain translucency and decrease deformity, while increasing the color of the product. Photomicrographs il-lustrated the grain structure.