Site description and Location The experiment was carried out at the experimental field of the Department of Agronomy and Haor Agriculture, Sylhet Agricultural University, Sylhet. Geographically the experimental field situated at 24° 54′ 33.2′′ N latitude and 91° 54′ 7.15′′ E longitude at the elevation of 30 m above the sea level. Laboratory location The grain quality test was done at the laboratory of Grain Quality and Nutrition (GQN) Division, Bangladesh Rice Research Institute (BRRI), Gazipur 1701, Bangladesh. Rice cultivar Twenty one local rice cultivars i.e. Akhnisail, Bantos, Biruin, Biruy, Botabiruin, Chinigura, Chinirsail, Chorabiruin, Gandi, HanoiTV, Kakhibiruin, Kalijira, Khakibiruin, Maloti, Monasail (red), Monasail (white) Moinasailbiruin, Muktasail, Mikirsail (Red), Mikirsail (White) and Nagrasail were collected from different parts of Sylhet (the north-eastern region of Bangladesh). Agronomic practices Seedlings were raised in well prepared seed bed at 21 July 2014 and twenty-six days old seedlings were transplanted in the field at 16 August following Randomized complete block design (RCBD) with three replications with the spacing of 20 cm × 15 cm in 10 m2 plots. Fertilizers were applied at the rate of 80, 40, 40 kg ha-1as N, P and K in the form of urea, TSP and MoP, respectively. The whole amount of TSP (Triple super phosphate), MoP (Muriate of potash) were applied as basal at the time of final land preparation and thoroughly incorporated into the soil. Urea was top dressed in three equal splits at 10, 25 and 45 DAT. Fertilizer dose was 180-40-40, N-P-K respectively. Harvesting was done within the first two weeks of December. After harvesting rice grain quality such as physical, chemical and cooking qualities were analyzed in the Grain Quality and Nutrition Division of Bangladesh Rice Research Institute (BRRI), Gazipur. Processing of rice cultivars Only whole rice grains without any physical damage or insect infestation was selected for analysis. The 200 g rough rice was dehulled by Satake rice mill to see chalkiness. The resulting brown rice was polished for 75 second in Satake grain-testing mill TM05. This polished rice was ground by a Cyclone sample mill. Physical properties One thousand whole rice grains without any physical damage or insect infestation were randomly selected and weighed separately. Milled rice outturn was expressed as percent of milled rice. Head rice outturn was determined by separating broken rice by hand and expressed as percent of head rice. Milled rice length and breadth (mm) were measured by slide calipers. The length of milled rice was divided by its breadth to determine the length to breadth ratio. In determining the size, milled rice was classified into three classes i.e. long (>6 mm in length), medium (5-6 mm in length) and short (<5 mm in length) (Dipti et al., 2003). For shape, the length:breadth ratio of milled rice was grouped into three: slender (ratio>3.0), bold (ratio 2-3) and round (ratio>2.0) (Dipti et al.,2003). Chalkiness of kernel is visually scored for the presence of white belly (dorsal side of the grain), white center (dorsal side in the center) and degree of translucency. Chalkiness were classified into four classes depending on presence of white belly, none, less than 10%, 10% to 20%, more than 20%.Grain appearance is largely determined by endosperm opacity, the amount of chalkiness either on the side of the grain or in the center and the condition of the eye or pit left after germ. Chemical properties Chemical properties like as amylose content was determined based on the Iodine-binding procedure as described by Juliano (1971). In brief, for 100 mg of rice flour, 1 ml of ethanol (95%) and 9 ml of 1 N NaOH were added in a volumetric flask (100 ml) followed by thorough mixing. Further, samples were heated on a boiling water bath for 10
Local rice cultivar, Chalkiness, Alkali spreading, elongation ratio75minute to gelatinize the starch and later on cooled to room temperature. Five milliliter of gelatinized starch solution was then transferred to a 100 ml volumetric flask followed by addition of 1 ml of 1N acetic acid and 2 ml of iodine solution, with the volume adjusted to 100 ml with distilled water. All the contents were thoroughly vortex mixed and allowed to stand for 20 minute. The absorbance was measured at a spectrophotometer. The amylose contents in samples was determined based on the standard curve prepared using potato amylose. Based on amylose content, milled rice was classified as Waxy (0-2%), Very low (3-9%), Low (>10-19%), Intermediate (>20-25%) and High (≥25%), (Juliano, 1972).Protein content was determined by Micro Kjeldahl method (AOAC, 1970). Nitrogen multiplied by a factor of 5.95, based on 16.8% nitrogen contained in the major rice protein fraction gluten (Juliano, 1966).Alkali Spreading Value was estimated by dispersing triplicate six whole milled rice grains in 10 ml 1.7% potassium hydroxide (KOH) for 23 h at room temperature and scored according to Little et al. (1958). The alkali spreading value classified into three classes corresponds to the gelatinization temperature, High (1.0-3.0%), Intermediate (4.0-5.0%) and Low (6.0-7.0%). Cooking propertiesCooking time was measured when 90% of cooked rice wastotally gelatinized. Imbibition ratio is the increase in volume of cooked rice over uncooked rice. Volume of cooked and uncooked milled rice was measured by water displacement method. Five gram of milled rice was placed in a graduated cylinder containing 50 ml of water and the change in volume was noted. For cooked rice volume 5 gm of milled rice was cooked and the cooked rice was placed in the same cylinder and the change in volume was measured. Elongation ratio was determined by the randomly selected of cooked rice length over the length of uncooked raw samples. Statistical analysisChemical properties data are the mean of three replications were presented in the Tables and standard deviation was done whenever necessary.