PROCESSING AND STORAGE OF INSTANT COOKED RICE

BANGLADESH RESEARCH PUBLICATIONS JOURNAL ISSN: 1998-2003, Volume: 7, Issue: 3, Page: 300-305, September - October, 2012 PROCESSING AND STORAGE OF INSTANT COOKED RICE M.A. Ali 1, S.M.K. Hasan 2, M.S. Mahomud 3 and M.A. Sayed 4 M.A. Ali, S.M.K. Hasan, M.S. Mahomud and M.A. Sayed (2012). Processing and Storage of Instant Cooked Rice. Bangladesh Res. Pub. J. 7(3): 300-305. Retrieve from http://www.bdresearchpublications.com/admin/journal/upload/09339/09339.pdf Abstract The study was progressed with the objectives of processing instant rice from scented rice (var. Kalijira) and evaluating effects of different processing techniques like boiling, steaming and pressure cooking on the physiochemical and organoleptic properties and studying storage stability in terms of shelf life. The milled raw rice was cooked, washed with distilled water, drained up and dried in a cabinet dryer. The instant rice was then stored at room temperature (21-32 0 C) after packaging in polyethylene bags. The proximate composition analysis revealed raw rice contained 12.65% moisture, 6.81% protein, 0.57% fat, 0.49% ash, 44.75% starch, 30.01% of total sugar, 0.22% crude fiber, and 79.48% carbohydrate, while instant rice processed by boiling contained 9.10% moisture, 5.20% protein,.27% fat, 0.48% ash, 64.21% starch, 17.12% of total sugar, 0.21% crude fiber, and 84.95% carbohydrate. The moisture, protein, fat, ash, starch, total sugar, crude fibre and carbohydrate contents were found respectively 9.15%, 5.25%, 0.26%, 0.47%, 64.87%, 19.03%, 0.22% and 84.87% when the rice was processed by steaming. The pressure cooked rice showed 9.08% moisture, 5.22% protein, 0.25% fat, 0.48% ash, 65.84% starch, 17.31% of total sugar, 0.22% crude fiber, and 84.97% carbohydrate. The sensory evaluation revealed that pressure cooking resulted in most acceptable instant rice rendering the scale Like very much. The stored instant rice showed a slight increase in moisture content and decrease in peroxide value after 24 weeks. The free fatty acid value was slightly increased from 0.99% to 1.18% after 10 weeks. A slightly rancid off flavor was noticed after 20 weeks which was increased significantly at 21 weeks. Besides, the instant rice took lower time (6.50 to 7.10 minutes) to cook as compared to traditional method. To obtain good quality instant rice, in terms of sensory attributes as well as overall acceptability, within few minutes instant rice should be processed through pressure cooking. Key words: Processing, Storage, Instant cooked rice Introduction Rice (Oryza sativa L.) belongs to the family Gramineae is the most widely consumed basic food stuff in the world. In 39 countries rice is the staple diet, but the dependence on rice for food energy is much higher in Asia than in other regions. Rice provides 35 to 59% of energy consumption for 2700 million people in Asia (FAO, 1984). As a primary food in many parts of Asia rice makes up anywhere between 55% and 80% of the caloric intake in countries such as Bangladesh, Cambodia, Indonesia, Laos, Thailand and Vietnam where the average eats upto 300 lb of rice a year (IRRI, 1988). Rice supplies not only the major energy source * Corresponding author:aslam_bau74@yahoo.com 1. Assistant Professor, Department of Food Science and Nutrition, Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur, Bangladesh 2. Assistant Professor, Department of Food Processing and Preservation, HSTU, Dinajpur, Bangladesh 3. Assistant Professor, Department of Food Engineering and Technology, HSTU, Dinajpur, Bangladesh 4. Assistant Professor, Department of Biochemistry and Molecular Biology, HSTU, Dinajpur

Processing and Storage of Instant Cooked Rice (carbohydrate) but also protein, vitamin and other nutrients (BRRI, 1996). Rice is the major cereal food in Bangladesh and the total production of rice was 25188 thousand metric tons under the cultivated area of 26615 thousand acres in the year of 2002-2003 (BBS, 2005). The cooked rice (parboiled) is one of the perishable foodstuffs. It can be contaminated easily with microorganisms that ferment the rice starch under room temperature. To prevent the cooked rice from microbial deterioration its moisture content should be reduced to 12-13 % and stored at suitable temperatures after packaging and sealing in food grade packaging materials. Recent concern with pathogens in ready to cook or ready to serve food is prompted by the considerable investigation relating to pre-harvest and post-harvest food safety (Hubbert et at., 1996). In Bangladesh per capita income has been increased and people s life styles are more active and busier nowadays. They have less time to relax and seek for food items that require lower time to process or ready-to-eat foods. In this study an attempt has been made to process instant cooked rice using locally available scented variety of Kalijira by different processing techniques like boiling, steaming and pressure cooking followed by observing the changes in proximate composition of the raw milled rice and instant rice and then evaluating the sensory attributes of the instant rice. To determine the shelf life of the instant rice the storage stability has also been studied. Materials and Methods Polished head rice from the variety of Kalijira was collected from local market of Dinajpur, Bangladesh for the preparation of instant cooked rice. AR grade chemicals were used in different chemical analyses and the shelf life of the cooked rice was studied by packaging it within the polyethylene bags followed by storing at room temperature for 24 weeks. Proximate composition of milled rice The scented and instant cooked rice were analyzed to determine and observe the nutritional changes in terms of moisture, protein, fat, total sugar and crude fiber contents by following the AOAC (1984) method. The starch content was determined by adopting the direct acid hydrolysis method as described by Ranganna (1992). According to Pearson (1976) the total carbohydrate content in the both rice was calculated by subtracting the estimated protein, fat, ash and moisture contents from 100. For storage studies in terms of shelf life the peroxide value and free fatty acid value in the instant rice were analyzed based on the methods as stated by Ranganna (1992) and the olfactory test was conducted with smell for the aroma detection of the stored instant rice. Processing of instant rice The instant cooked rice was prepared by conducting different processing techniques including boiling, steaming and pressure cooking. The cooked rice was washed with distilled water and drained for 5 min and dried in a cabinet dryer (Model OV-165, Gallen Kamp Company) at 50 0 C until its final moisture content was about 9%. Determination of solid losses from instant rice The solid loss as well as cooking loss was calculated by subtracting the solid content in instant cooked rice from that in the raw rice. 301

Ali et al. Sensory evaluation of instant rice The consumers preferences towards the overall acceptability of the developed instant rice were evaluated by a taste-testing panel in terms of Hedonic Rating Test. The panelists were selected from the students of Master of Science in Food Engineering and Technology, Hajee Mohammad Danesh Science and Technology University, Dinajpur, Bangladesh. The samples were served to the panelists and asked to assign appropriated scores for the quality attributes like color, flavor, texture and overall acceptability based on 9 different scales such as 9 = Like extremely, 8 = Like very much, 7 = Like moderately, 6 = Like slightly, 5 = Neither like or dislike, 4 = Dislike slightly, 3 = Dislike moderately, 2 = Dislike very much and 1= Dislike extremely. Results and Discussion Proximate Composition of raw milled rice The milled scented rice used for processing of instant rice was analyzed for moisture protein, fat, ash, starch, total sugar, crude fiber, and carbohydrate contents. Table 1. Composition of Scented rice (var. Kalijira) Condition Composition (%) of rice * Moisture * Protein * Fat * Ash * Starch * Total * Crude * Carbohydrate Sugar fibre S1 12.65 6.81 0.57 0.49 44.75 30.01 0.22 79.48 S2 9.10 5.20 0.27 0.48 64.21 17.12 0.21 84.95 S3 9.15 5.25 0.26 0.47 64.87 19.03 0.22 84.87 S4 9.08 5.22 0.25 0.48 65.84 17.31 0.22 84.97 S1 = raw scented rice S2 = instant rice processed by boiling S3 = instant rice processed by steaming S4 = instant rice processed by pressure cooking * Values were calculated on wet weight basis The moisture content of the rice was 12.65% which was higher than that found by McCance and Widdowson (1995) who reported about 11.40% moisture in raw milled rice, and lower than those found by McCall et al. (1951) and Ali et al. (1992) who mentioned 13.2% and 13.7% respectively. The rice contained 6.81% of protein which was significantly higher than the value mentioned by Juliano (1972) who reported 5.40% protein in the milled rice. The obtained protein content was significantly lower than the value as stated by Kik and Williams (1945) who mentioned 7.6%. The fat content of the milled rice was 0.57%. This value was significantly higher than that found by Grist (1965) who mentioned 0.3-0.4% fat, and similar to that found by Platt (1939) who reported 0.37% fat in raw milled rice. The ash content of the rice was 0.49% which was significantly lower than the content found by Rosedale (1939) who obtained 0.9 % ash and slightly higher than those found by Grist (1965) and Juliano (1972) who reported respectively 0.36% and 0.3% ash in the milled rice. The starch content of rice was about 44.75%. About 30% of total sugar was found in milled rice after polishing. The crude fiber content (0.22%) of the milled raw rice was slightly lower than those found by Rosedale (1939), and Houston and Kohler (1970) who found respectively 0.4% and 0.3%. The crude fiber content of the rice was slightly higher than the value as mentioned by Platt (1939) who found 0.16%, and nearly similar to the content found by Kik and Williams (1945) who obtained 0.2%. The carbohydrate content of the milled rice was 79.48% which was significantly lower than the values as described by Platt (1939) and Rosedale (1939) who obtained respectively 90.79% 302

Processing and Storage of Instant Cooked Rice and 91.4%, and nearly similar to the content found by Kik and Williams (1945) who reported about 79.0% carbohydrate in raw milled rice. Composition of instant rice The moisture content of instant rice ranged from 9.08-9.15% which was lower than the values as stated by Damir (1991) who found 10-12%. The highest moisture content (9.15%) was found for sample S3 while the sample S4 showed the lowest moisture content (9.08) indicating the lower water activity of the instant rice. It was observed that the protein content of the instant rice was highest (5.25%) for sample S3 and lowest one was in sample S2. The observed protein content (5.20-5.25%) was much lower than the original milled rice as reported by Houston and Kohler (1970) who reported 6.7% protein in the milled rice. The reduction of protein content from the instant rice might be due to the gelatinization or denaturation of the protein and leaching out from the rice during cooking and washing. The fat content (0.25-0.27%) of the instant rice as shown in Table 1 was approximately similar to the value as reported by Damir (1991) who found o.29% fat in the instant rice. The ash content ranged from 0.47 to 0.48% in instant rice was approximately similar to the raw scented rice (0.49%), describing no significant change in ash content of rice due to cooking and washing, but slightly lower than that found by Houston and Kohler (1970), who reported 0.50% ash in milled rice. The highest starch content (65.84%) was found in sample S4 while sample S2 showed the lowest content (64.21%). The observed starch content as shown in Table 1 described that processing of instant rice by pressure cooing significantly reduced the loss of starches in the instant rice which might be due to lower processing time by pressure cooker. The total sugar content was drastically reduced in the instant rice (17.12-19.03%) as compared with the raw scented rice (30.01%). The sample S3 contained the highest total sugar (19.03%) while samples S2 and S4 contained 17.12% and 17.31% respectively. Due to the processing of instant rice average loss of total sugar as calculated from Table 1 was 40.62% which was significantly higher than that reported by Cheigh et al. (1977) who found only 2.32% solid loss in the instant rice prepared from Indica variety of rice. This reduction might be occurred due to excessive leaching out of sugar from the rice during cooking and washing. The instant rice contained 0.21-0.22% crude fiber which was significantly lower than the value found by Damir (1991) who reported 1.60% crude fiber in enriched instant rice processed in Australia. The observed crude fibre content of the instant rice was similar to the crude fibre in raw rice (0.22%) which indicates the fact that processing treatments of instant rice usually do not affect the crude fibre content. The total carbohydrate content of instant rice samples were ranged from 84.87 to 84.97% (Table 1). The highest amount (84.97%) was found in sample S4 followed by samples S2 (84.95%) and S3 (84.87%). The total carbohydrate content of the instance rice samples under this study was slightly higher than that found in Australian instant rice which is about 83.59% (Damir, 1991). Cooking Time Different techniques required different cooking times for processing of the instant rice. For complete cooing boiling took about 7.10 min while steaming and pressure cooking took about 7.00 and 6.10 min respectively. Effects of processing techniques on sensory attributes The sensory attributes like color, flavor and texture of the instant cooked rice were significantly varied based on different processing techniques including boiling, steaming and pressure cooking. After boiling the rice secured lower score (6.13) in terms of Like slightly for texture while the score (7.24) indicating Like moderately was obtained by the rice for color, flavor and texture when 303

Ali et al. processed by steaming. The rice processed by pressure cooking secured the highest score (8.02) describing Like very much in preference with texture, taste, color, flavor and overall acceptability. Storage studies of instant Rice In order to determine the shelf life of the instant rice different analytical tests in terms of moisture uptake, peroxide value and free fatty acid value, and aroma detection were conducted with the stored rice. Initially the rice contained about 12% of moisture which reached 13.71% after storage of 24 weeks. This moisture uptake might be due to improper packaging technique (e.g. not properly sealed) and a high relative humidity of the ambient air entering into the bags. The peroxide value of the rice was slightly decreased as compared to the initial value after 24 weeks of storage. No significant difference was observed in the rice for free fatty acid value until 8 weeks of storage but this value was slightly increased from the initial value of 0.99% to 1.18% after 10 weeks of storage. The instant rice showed no significant difference in terms of aroma until 20 weeks but a slightly rancid odor was noticed after 20 weeks which was increased significantly by 21 weeks. Conclusion Nowadays higher income and more active as well as busier life style result in consumers seeking for high quality and convenient food items in the market. The instant rice developed in this research with excellent shelf-life has potentials to meet today s demands not only in Bangladesh but also in the overseas markets. Besides, production of the rice includes simple processing techniques, cheap and easy packaging systems with longer shelf life that may result in more profitable return to the processors by decreasing production and distribution costs. In comparison with other processing techniques pressure cooking would result in more acceptable products in terms of different sensory attributes like color, flavor, texture and overall acceptability, and requires less cooking time. References Ali, M.K., M.A. Malek and K. Jahan. 1992. Nutrition of local foods, Institute of Food Science and Nutrition, University of Dhaka, Bangladesh AOAC. 1984. Official Methods of analysis of the Association of Official Analytical Chemists, 15 th Ed. Washington D.C. USA BBS (Bangladesh Bureau of Statistics). 2005. Statistical Year Book of Bangladesh Statistical Division, Ministry of Planning, Govt. of Bangladesh BRRI (Bangladesh Rice Research Institute). 1996. Annual report for 1995, BRRI, Gazipur, Bangladesh Cheigh, H.S., C.H. Ryu, J.S. Jo and T.W. Kwon. 1977. Effect of washing on the loss of nutrients of rice, Korean J. Food Sci. Technol., 9: 170-174 Damir, A.A. 1991. Preparation and evaluation of quick-cooking raw milled and parboiled rice. Assiut J.Agric. Sci., 22(4): 103-123. FAO (Food and Agriculture Organization). 1984. Food balance sheets, 1979-81 average. Grist, D.H. 1965. Rice. Longmans, Green and Co. Ltd. London Houston, D.F. 1970. Nutritional properties of rice. Nat. Acad. Sci., Washington, D.C. USA 304

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