Effect of cooking on amylose content of rice Essay Example for Free

Effect of cooking on amylose content of rice Essay In diabetes type 2, there is a deficiency of insulin which results in improper/ slow breakdown of food. This results in sugar level spikes immediately after a meal, which can be harmful. Hence, diabetics must have food stuffs which have a slow release rate so as to not cause any spikes. In order to find out the most suitable method of cooking rice for diabetic patients, we found out the amylose content of rice cooked by different methods and co-related it with Glycemic Index (GI). Glycemic Index is release of glucose in the blood by the breakdown of carbohydrates. Higher the glycemic index, faster breakdown of food and thereby more release of glucose in the blood, so immediate requirement of insulin, which can be toxic for diabetic patients. Glycemic index and amylose content are inversely proportional to each other. There is a wide variation in the amylose content of rice depending on the way it is cooked. In this paper, the effect of cooking on amylose content of rice is described using various experimental approaches. Various method of cooking involves traditional method, microwave and steam cooked method. The amylose content of the rice is then co-related with its glycemic index. Keywords: Rice; Glycemic Index; Amylose Content; Diabetes; Cooking. INTRODUCTION Rice is the most important staple food for a large part of the worlds human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies [6]. The awareness of the general public related to health foods has been on the rise recently and people are looking for the right variety of rice and more efficient methods of cooking it for diabetics. Due to the low insulin concentration in the body, the release of sugar into blood is less controllable than normal, leading to spikes in blood sugar after meals for them. High blood sugar, if left untreated, can cause dehydration, electrolyte imbalance etc. over short term and retinopathy, nephropathy over long term. Hence, this is an acute problem faced by all diabetics. Brown rice is obtained directly from the plant and is rich in nutrients like vitamin B1, B3 and minerals like iron which can be used in preventing deficiency diseases like beriberi etc. [8]. The nutrient content of consumable rice varies with the processing techniques. For example, brown rice undergoes minimal processing and thus retains most 385 Pelagia Research Library Ashish Jain et al Euro. J. Exp. Bio. , 2012, 2 (2):385-388 of the original nutrients within the grain, whereas white rice or polished rice is devoid of most of the nutrients as they are pushed into the husk of the grain during processing which is then removed during polishing [9]. Similarly, the starch content also varies with the cooking methods viz., traditional methods or home-made or microwaved method etc. [6]. Rice contains two types of starch in rice: amylose and amylopectin. Amylose is a long straight starch molecule that does not gelatinize during microwave cooking [4] and hence rice with more amylose content tends to cook fluffy, with separate grains. Besides, amylose also hardens and forms during crystals during cooking and melts when the rice is re-heated. Rice that is high in amylose has a lower Glycemic Index number [1, 7]. This is because amylose is harder to break down than simple sugars like glucose etc.and ensures a sustained release of sugar into blood without spiking immediately after a meal. MATERIALS AND METHODS The following reagents are used for estimation of amylose content and for preparation of standard: 95% Ethanol: Prepared from 100% Ethanol 1N NaOH, Iodine Potassium iodide solution Standard amylose: Obtained from HIMEDIA 1N Acetic acid: From NICE Chemicals Glassware: Borosil Water bath: High Precision water bath from Acmas was used Spectrophotometer: From Amersham Biosciences to measure OD Cuvette: Quartz Cuvette to measure OD. Software: HandyGraph Software to draw graph 1N NaOH solution: Dissolve 40g of NaOH in 1000ml distilled water 1N Acetic acid solution: Dilute 57. 5 ml glacial acetic acid to 1000ml using distilled water Iodine Potassium iodide solution: Dissolve 0. 26 g of Iodine in 10 ml of Potassium iodide solution containing 2. 6 g of KI Standard Amylose Solution: Take 40mg of pure potato starch (amylose) in a 100 ml volumetric flask and add 1 ml of 95% ethanol and 9. 0 ml of 1N NaOH. Shake well and boil over water bath for 10 minutes and make up the solution to 100 ml using distilled water. Method: We weighed 100 mg well powdered milled rice into 100 ml volumetric flask and to it 1 ml 95% ethanol and 9 ml 1 N NaOH was added. The sample was heated for 10 minutes in boiling water bath, cooled and the volume was made up to 100 ml. 5 ml was pipetted from the 100 ml into another 100 ml volumetric flask. To it 1 ml I N acetic acid and then 2 ml iodide solution were added and the volume was made up to 100 ml. The mixture was stirred and allowed to stand for 20 minutes and the per cent Transmittance at 620 nm was determined using a colorimeter. A series of standard starch solution containing 0, 20, 40, 60, 80 and 100% amylose was prepared as in the steps 1 to 5. The transmittance of the standards was read at 620nm and a standard graph was plotted. Amylose content of the sample was determined in reference to the standard curve and expressed on percent basis. RESULTS In Table 1, five different amylose solutions were prepared at different concentrations and the absorbance values at 620nm were noted down. The absorbance readings were triplicated for standard amylose and standard graph was obtained as follows: 386 Pelagia Research Library Ashish Jain et al Euro. J. Exp. Bio. , 2012, 2 (2):385-388. Table 1: Preparation of Standard Graph from Amylose Amylose Concentration (mg/mL) Blank 8 16 24 32 40 Abs @ 620 nm T1 T2 T3 0 0 0 0. 079 0. 072 0. 077 0. 156 0. 156 0. 149 0. 239 0. 24 0. 239 0. 321 0. 32 0. 33 0. 40 0. 40 0. 40 Avg. Abs 0 0. 076 0. 153 0. 239 0. 323 0. 40 Std. Deviation T1 T2 T3 0 0 0 +0. 003 -0. 004 +0. 001 +0. 003 +0. 003 -0. 004 0. 000 +0. 001 0. 000 -0. 002 -0. 003 +0. 007 0. 000 0. 000 0. 000. This table is used in making the graph shown below. The procedure followed to obtain these readings is described in the Materials and Methods section. T1, T2, and T3 are the triplicated values. Scale X Axis: 1cm 8mg/ml Y Axis: 1cm 0. 08OD A b s o r b a n c e A b s o r b a n c e Amylose concentration Amylose concentration A b s o r b a n c e Amylose concentration Figure 1: The above graphs are obtained by taking Concentration on the X-axis and Absorbance at 620nm on the Y-axis for each of the set of values. 387 Pelagia Research Library Ashish Jain et al Euro. J. Exp. Bio., 2012, 2 (2):385-388. Table 2: Extrapolated values of rice cooked by different methods Cooking Method Steam Cooked Traditional Method Microwaved Raw Abs @ 620 nm T1 T2 T3 0. 169 0. 172 0. 171 0. 195 0. 194 0. 196 0. 227 0. 227 0. 230 0. 258 0. 259 0. 259 Avg. Abs 0. 171 0. 195 0. 228 0. 259 Amylose Concentration (mg/mL) 17. 35 19. 67 22. 98 25. 99 This table lists the amylose content of rice which is cooked by different methods. The values are obtained from extrapolating from the standard amylose curve. DISCUSSION. Table 3: Co-relation between amylose content and Glycemic index of rice [8] If Amylose content is high Amylose content is low Then Low Glycemic Index and the rice grains will show high volume expansion (not necessarily elongation) and a high degree of flakiness. The rice grains cook dry, are less tender, and become hard upon cooling. High glycemic Index and the rice grains will cook moist and sticky It is seen that amylose content is inversely related to the Glycemic index. From table 2, it is observable that the amylose content of microwaved rice is highest after raw, uncooked rice. Hence, this method of cooking rice is the most suitable for diabetic patients as the Glycemic Index will be lowest. Since the Glycemic Index is low, the breakdown rate is slower, which prevents the sugar levels in blood from spiking just after a meal. REFERENCES [1] DJ Jenkins et al. (1981). Am J Clin Nutr 34; 362–366. 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