EFFECT OF PROCESSING ON NUTRIENT COMPOSITION AND BIOACTIVE COMPONENTS OF SELECTED RICE VARIETIES OF ASSAM
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Date
2019-07
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AAU, Jorhat
Abstract
A study was carried out with the objective to determine the effect of processing on physico- chemical properties and bioactive compounds of selected red rice varieties of Assam. Seven red pigmented rice varieties were selected and procured from Krishi Vigyan Kendra, Silapathar, Dhemaji. A series of laboratory tests were performed on both the uncooked and cooked forms of dehusked and 6 per cent polished rice samples to find out the physico- chemical properties, mineral content and the bio- active compounds. The dehusked and polished rice yield of the selected red rice varieties was found to be in the range of 68.33±0.52 to 75.23±0.47 per cent and 64.14±0.39 to 73.67±0.69 per cent, respectively. Head rice yield (HRY) and broken rice yield (BRY) of the varieties ranged from 55.13±0.99 to 73.93±0.73 per cent and 0.93±0.16 to 13.60±0.58 per cent, respectively and polishing of the rice grains decreased HRY (40.82±1.12 to 67.44±1.23 per cent) but increased the BRY (2.96± 0.19 to 23.15±1.06 per cent). Length, breadth, thickness and length/breadth ratio of the dehusked rice samples ranged from 5.00±0.33 to 5.90±0.32 mm, 2.10±0.21 to 2.75±0.35 mm, 1.59±0.14 to 2.03±0.02 mm and 1.89±0.40 to 2.85±0.36, respectively. Thousand grain weight, volume and bulk density ranged from 13.46±0.00 to 19.40±0.00 g, 16.67±0.29 to 25.83±0.29 ml and 0.69±0.01 to 0.88±0.01 g/ml in the dehusked samples. The length, breadth, thickness, thousand grain weight and thousand grain volume of rice varieties significantly (p≤0.05) reduced on polishing, whereas the length/ breadth ratio and bulk density increased. Water absorption capacity (WAC), cooking time and grain elongation ratio of the dehusked rice samples ranged from 2.06±0.16 to 2.77±0.21 ml/g, 21.66±1.53 min. to 38.33±1.15 min. and 0.98±0.01 to 1.14±0.02. Water absorption capacity and grain elongation ratio significantly (p≤0.05) increased whereas the CT decreased significantly (p≤0.05) on polishing. The dehusked samples had 11.64±0.08 to 12.75± 0.04 g/100 g of moisture,
9.31±0.00 to 13.50± 0.66 g/100 g of crude protein, 2.53± 0.09 to 3.71±0.04 g/100 g of crude fat, 0.56±0.01 to 0.81±0.03 g/100 g of crude fibre, 1.24±0.01 to 2.60±0.03 g/100 g of total ash, 68.60±1.44 to 73.87±0.18 g/100 g of carbohydrate and 352.99±0.80 to 361.86±2.78 kcal/100 g of energy. The crude protein, crude fat, crude fibre and total ash content decreased significantly (p≤0.05) on polishing as well as cooking. The carbohydrate content significantly (p≤0.05) increased on polishing as well as cooking. The dehusked samples had iron, zinc, calcium, phosphorus and magnesium content in the range of 4.47±0.18 to 12.46±0.63 mg/100g, 1.41±0.11 to 2.93±0.05 mg/100 g, 9.96±0.11 to 37.73±0.58 mg/100g, 134.54±3.44 to 221.57±3.48 mg/100 g and 0.13±0.01 to 1.21±0.00 mg/100 g, respectively. Polishing significantly (p≤0.05) reduced the iron, zinc, calcium, phosphorus and magnesium content. Cooking of the rice samples showed no significant (p≥0.05) change in the iron, zinc, calcium content on cooking, while magnesium content reduced significantly (p≤0.05). No significant (p≥0.05) change in phosphorus content was seen in the dehusked samples, whereas the polished samples showed significant (p≤0.05) loss of phosphorus upon cooking. The bioactive compounds were determined in terms of total antioxidant capacity (TOA), total anthocyanin content (TAC), total phenolic content (TPC), total flavonoid content (TFC) and total carotenoid content (TCC) and were observed to significantly (p≤0.05) decreased on polishing as well as cooking. The TOA, TAC, TPC, TFC and TCC of the dehusked samples ranged from of 44.67±0.45 to 81.08±0.45 per cent, 11.35±0.45 to 23.71±0.94 mg/100 g, 46.13±0.88 to 109.50±0.64 mg GAE/100 g, 12.24±1.19 to 39.23±1.59 mg QE/100 g and 0.42±0.02 to 1.85±0.07 μg/100 g, respectively. The present study provides the evidence that polishing and cooking of the rice grains has significant effect on the physical and nutrient quality of the rice varieties. The variety Kaoi Jamfri showed better mineral content and antioxidant capacity than rest of the varieties and can be recommended for popularization among rural and urban population. Further studies may be taken out to find out the degree of polishing at which maximum milling recovery and retention of nutrient takes place. The rice varieties may be used to formulate supplementary food mixes, develop rice based products. The unpolished rice varieties may be recommended for consumption to prevent nutrient deficiencies among the people. Further studies can be taken out to study the use of the rice bran to formulate functional food.