International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 3, March – 2019, Pages: 12-18 http://www.ijeais.org/ijaar 12 Effect of Far Infra-Red Radiation on Paddy Parboiling and Milling Qualities A.M.M.Irfeey 1 , A.B.F. Husna 2 , A.L.M. Rifky 1 1 Department of Biosystems Technology, Faculty of Technology, Eastern University, Vantharumoolai, Chenkallady, Sri Lanka. 2 Zahira college, Anuradhapura, Sri Lanka. Abstract: Paddy parboiling is a hydrothermal process applied as a treatment to rough rice, prior to normal milling stage. The parboiling process consists of three separate operations as; soaking, steaming and drying. The traditional parboiling soaking process needs high water consumption, causes high water pollution, air pollution and high energy consumption than using far –infrared (FIR) method. This study was conducted to use the FIR on parboiling process and to test quality of milled rice. The paddy sample BG358 (1kg) was selected and measured its initial moisture content and different soaking moisture contents from the sample were prepared as: 22%, 25%, 28% and 31% respectively for parboiling. Parboiling process was done at 175 0C for 20s by using FIR in 3 different distances as: 20cm, 30cm, 40cm and 3 replicates for each samples and rice cooker (100 0C, 25 min) used as control method. Milling qualities of par boiled rice were tested. The white belly rice percentage and broken rice yield percentage were significantly low in samples soaked up to 28% and the total rice yield and head rice yield were not significantly difference with control samples. The selected qualities were not influenced by various radiation intensities while the white belly rice only showed significantly less yield in 30 cm distance. The energy consumption of FIR was 0.005445kWh while the energy consumption was 0.416 kWh from traditional method. Moisture content of soaked paddy was identified as main cause for broken paddies. Keywords; Par boiling, milling, soaking, steaming, drying, far-infrared (FIR) 1. Introduction Parboiling is an old method of rice processing, widely used in most of the developing countries. The process of parboiling are three-stages: soaking, gelatinization and drying (Das et al., 2004). Treatment of parboiling: gelatinizes the rice starch, improves the hardness of the rice upon drying and minimizes the breakage losses and thus increases the milling yield ( Poritosh Roy et al., 2011). The starch gelatinization brings about changes in the physicochemical properties of the rice (Bualuang et al., 2012). Parboiling prolongs storage life, allows easier hulling of the grains, makes the grain harder, produces less broken during milling ,reduces breakage and also facilitates the breakdown of protein bodies as well as adding a characteristic colour (Imonigie et al., 2017), reduces insect attack on the grain and increases vitamin B content of grain (Toktok, 2003). Parboiled rice has lower nutrient loss during milling and cooking corresponding to percentage of ash enrichment and high content of mineral and nutrient matter compared with the milled rice (Bualuang et al., 2012). Texture and flavour to the rice also increase the nutritive value during parboiling. It also increases the market value (Imonigie et al., 2017), and is preferred by some people for its taste (Toktok, 2003) and paddy with a high initial moisture content >22% wb is found to be suited for parboiling by this technique (Das et al., 2004). One of the consequences of this pre-treatment is an increase of moisture content to 35% (wb). Hence it is essential to reduce the moisture to 14% (wb) prior to further processing (Das et al., 2004). Parboiling prolongs storage life, allows easier hulling of the grains, makes the grain harder, produces less broken during milling, reduces breakage and also facilitates the breakdown of protein bodies as well as adding a characteristic colour (Imonigie et al., 2017), reduces insect attack on the grain and increases vitamin B content of grain (Toktok 2003). Parboiled rice has lower nutrient loss during milling and cooking corresponding to percentage of ash enrichment and high content of mineral and nutrient matter compared with the milled rice (Bualuang et al., 2012). Texture and flavour to the rice also increase the nutritive value during parboiling. It also increases the market value (Imonigie et al. 2017), and is preferred by some people for its taste (Toktok 2003). Demand for brown rice and parboiled rice are increasing International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 3, March – 2019, Pages: 12-18 http://www.ijeais.org/ijaar 13 because of their reputation for nutritional excellence and health claims associated with eating this type of rice (Parnsakhorn & Noomhorm 2008). It is special one in health food and green organic products. But, it requires more energy and time for cooking of parboiled rice (Poritosh Roy et al., 2003). Parboiled rice has been produced by both traditional and modern methods. Modern methods are energy and capital intensive, and are not suitable for small scale operation at the village level (Poritosh Roy et al., 2003). The traditional method is time consuming and often laborious, and the end products are always below the required quality desired by the consumers. The traditional parboiled rice still doesn't meet the required standard of storage (Imonigie et al. 2017). In the process, the paddy is soaked, steamed and redried before milling. This process greatly affects the milling, storage, cooking and eating qualities of rice. Parboiling can be mechanized or carried out in simple traditional forms (Toktok 2003). Infra-red radiation heating operation is relevant to many industrial heating and drying process because, it can achieve rapid and contactless heating. Specific advantages of IR heating compared with conduction and convection heating are reduced heating time, uniform heating, reduced quality losses, absence of solute migration in material, versatility, simplicity, compact equipment and energy saving (Zhongli Pan and Griffiths Gregory Atungulu, 2010). Infrared (IR) is used for heating of food stuffs for different purposes like drying, cooking, baking, roasting and blanching. IR heating technique to be fit for drying of heat-sensitive products like rice (Dariush Zare et al., 2015.). Its ability to reduce the drying time has been reported by several researchers who dried a variety of food products such as rice, potato, barley, welsh onion, banana and citrus presscakes (Nathakaranakule et al., 2010). Combining FIR with some other drying processes could also improve the quality of dried products, i.e. head rice yield of paddy , hardness of dried banana slices and fresh condition of onion (Nathakaranakule et al., 2010). 2. Materials and methodologies Paddy sample (variety BG 358) was cleaned and separated from immature, undersize and oversize, stones, dust and chaff by using paddy cleaner device and prepared. Initial moisture content of paddy sample was measured by using oven dry method (Gravimetric method). Then, soaked into 4 different volumes of water samples to create different moisture contents. 1kg of paddy sample was filled in each bottles and air tied and shacked in regular interval for 21days and moisture contents of the 4 volumetric water filled samples were calculated and mean time traditional soaking method also done. Samples were processed for parboiling by using FIR machines and traditional method sample was processed to parboil by using rice cooker. In FIR parboiling method, three radiation intensities (three 15 cm x 5 cm ceramic electric IR modules (660 W each) mounted at the top of the apparatus) of FIR machine with three different distances (20cm, 30cm and 40cm) were tested for parboiling. Then final moisture content of the parboiled rice sample were measured by using moisture meter and after allowed to reach room temperature by spreading in the large pan. The moisture content of dried parboiled rice is determined as 14 ± 0.3% (wet basis) and the dried parboiled paddy from each samples were sent to determine the milling quality of rice. Sample of 250g is weighed to the nearest 0.1g and de-husking was carried out by using laboratory husker. The whitening of brown rice is carried out to a bran removal of 7.0 ± 0.5% by using laboratory polishing machine. 2.1. Testing of milling quality of rice The milling quality of the dried parboiled paddy was calculated using following equation (Sahay and Singh 2006). 100      P MR W W TMY TMY = Total milling yield WMR = Total weight of milled rice WP = Paddy weight 2.2. Head rice yield The head rice yield of dried parboiled paddy was calculated using following equation (Sahay and Singh 2006). International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 3, March – 2019, Pages: 12-18 http://www.ijeais.org/ijaar 14 100      MR HR W W HRY HRY = Head rice yield WHR = Weight of head rice WMR = Weight of milled rice 2.3. The percentage of broken The selection of broken rice percentage was done manually based on broken grains, which were less than 1⁄2 broken of rice kernels. Then the broken percentage was expressed as a percentage of milled rice weight. The percentage of broken of milled rice was calculated using following equation (Sahay and Singh 2006). 100      MR BR W W BP BP = Broken percentage WBR = Weight of broken rice WMR = Weight of milled rice 2.4. The percentage of white belly The percentage of white belly of milled rice was calculated using following equation (Sahay and Singh 2006). 100      MR WB W W WBP WBP = Percentage of white belly WWB = Weight of white belly WMR = Weight of milled rice 2.5. The percentage of discolored grains The percentage of discoloured grains of milled rice was calculated using following equation (Sahay and Singh 2006). 100      MR DG W W DGP DGP = Discoloured grain percentage WDG = Weight of white belly WMR = Weight of milled 2.6. Energy estimation Measured energy consumption of rice cooker (1000W) and FIR heater (1980W). (Fernando 2015), EEnergy (kWh) PPower (w) TTime (h) Results and Discussion 4.1 White belly percentages 4.1.1 White belly percentage with moisture changes There was a significant relationship between moisture level and the white belly percentage. Moisture with 28% was the low percentage value of white belly rice and moisture with 36.7% was the high percentage value of white belly rice (Figure 1). 4.1.2 White belly percentage with radiation distance There was a significant relationship between radiation intensities and white belly percentage. Radiation intensity of 30cm distance was low in percentage and 40cm distance was high in percentage (Figure 2). 4.2 Broken rice percentage 4.2.1 Broken rice percentage with moisture changes We have determined the broken rice % changes with moisture contents of soaked paddy. There is a significant change between the broken rice % and moisture changes of soaked paddy. The moisture content of 28% is showing least broken rice %. The moisture levels (25%, 28%, 31%) are showing significant different in broken rice % with control level and 22% moisture content (Figure 3). 4.2.2 Broken rice percentage with radiation distance We have measured broken rice % with radiation intensity using FIR machines. It is showing a significant change between broken rice % and radiation intensities. The intensity 30 cm is having less broken rice % but other intensities (20 cm, 40 cm) are having high broken rice %. Although mean value is not showing a significant change with International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 3, March – 2019, Pages: 12-18 http://www.ijeais.org/ijaar 15 control levels (Figure 4). 4.3 Discolor percentage 4.3.1 Discolor grain percentage with moisture changes We have measured Discolour grain % with moisture changes of soaked paddy. It is showing a significant difference between the Discolour grain % and moisture changes of soaked paddy. The moisture level 22% is having a high Discolour grain %. All other moisture levels are not showing significant difference with control level (Figure 5). 4.3.2 Discolor grain percentage of radiation distance We have measured Discolour grain % with radiation intensity of FIR machines. It is not showing a significant change between Discolour grain % and radiation intensities. The intensity 30 cm is having less Discolour grain % but other intensities (20 cm, 40 cm) are having high Discolour grain percentage. Although mean value is not showing a significant change with control level (Figure 6). Figure 1. Effect of moisture on white belly percentage Figure 2. Effect on radiation distance on white belly % Figure 3. Effect moisture on broken rice (Mean) Figure 4. Effect of radiation distance of soaked paddy on broken rice % Figure 1. Effect of Moisture on White Belly % International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 3, March – 2019, Pages: 12-18 http://www.ijeais.org/ijaar 16 4.4 Head rice yield percentage 4.4.1 Head rice yield percentage with moisture changes We have measured Head rice yield % with moisture changes of soaked paddy.it is not having a significant difference between the Head rice yield % and moisture changes of soaked paddy. The moisture level 28% is showing high Head rice yield % compared with other moisture levels (Figure 7). 4.4.2 Head rice yield percentage of radiation distance We have measured Head rice yield % with radiation intensity of FIR machines. It is not showing a significant change between Discolour grain % and radiation intensities. The intensity 30 cm is having high Discolour grain % than the other intensities (20 cm, 40 cm) (Figure 8). 4.5 Total rice yield percentages 4.5.1 Total rice yield percentage with moisture changes We have measured Total rice yield percentage with moisture changes of soaked paddy.it is not having a significant difference between the Total rice yield % and moisture changes of soaked paddy. Control level is showing high total rice yield, but the other levels of moisture showing lower total rice yields (Figure 9). 4.5.2 Total rice yield percentage of radiation distance We have measured Total rice yield % with radiation intensity of FIR machines, it is not showing a significant change between Total rice yield % and radiation intensities, control is showing the high total rice yield (Figure 10). Figure 7. Effect of moisture on head rice yield % Figure 8. Effects of radiation distance of head rice yield % Figure 5. Effect of moisture on discolour grains % Figure 6. Effect of radiation distance of soaked paddy on discolour grains % International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 3, March – 2019, Pages: 12-18 http://www.ijeais.org/ijaar 17 Moisture% White belly% Discolour grain% Broken rice% Head rice yield% Total rice yield% 22% 6.46±4.38 16.65±1.657 1.759±2.744 73.3±3.00 74.61±2.88 25% 1.48±1.971 4.24±1.368 0.423±5.158 75.29±5.49 75.74±5.26 28% 0.04±0.534 5.90±1.528 0.293±4.748 77.58±4.95 77.87±4.75 31% 0.02±1.55 4.04±1.704 0.577±4.33 75.43±3.26 76.79±4.34 36.7% 7.69±5.04 5.98±2.04 1.022±2.285 77.52±1.83 82.54±1.58 Intensity (cm)] White belly% Discolour grain% Broken rice% Head rice yield% Total rice yield% 20 1.533±2.851 6.11±3.88 0.84±0.601 75.01±3.63 77.56±2.58 30 1.033±1.875 4.71±3.146 0.446±0.593 75.32±2.34 77.49±2.18 40 3.42±4.60 7.81±3.54 0.993±1.31 74.12±5.82 76.2±5.8 Control 7.69±5.04 5.98±2.04 1.022±2.285 77.52±1.83 82.54±1.58 Conclusion According to this research study, the moisture content significantly changed with white belly%, discolour grain%, broken rice%. Total rice yield and Figure 9. Effect of moisture on total rice yield % Figure 10. Effect of radiation distance of total rice yield % Table 1. Effect of radiation distance of total rice yield % Table 2. Mean value of Radiation intensities and milling qualities International Journal of Academic and Applied Research (IJAAR) ISSN: 2000-005X Vol. 3 Issue 3, March – 2019, Pages: 12-18 http://www.ijeais.org/ijaar 18 head rice yield % were not significantly changed with moisture contents. White belly % and broken rice % were significantly changed with radiation distance but all other properties as discolour grain%, broken rice yield%, total rice yield% and head rice yield% were not expressed any significant changes with radiation distance. Far infra-red radiation method is an effective method considering energy consumption. References Bualuang, O., Tirawanichakul, Y. Tirawanichakul, S., (2012). 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