The Glycamic indices of different varieties of rice in Sri Lanka
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Date
2000
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University of Sri Jayawardenepura: USJ(MED).
Abstract
Glycaemic index is an important indicator of the physiological effect of consumption of food. It is defined as the glycaemic response after consumption of a 50g carbohydrate portion of food expressed as a percentage on that of an equal carbohydrate portion of a standard, usally white bread or glucose. The glycaemic index indicates how rapidly the bliid glucose levels change on consumption of different foods containing carbohydrates. Hence glycaemic index is beneficial in the management of diabetes mellitus, coronary heart disease, obesity as well as in sports medicine. In Sri Lanka since rice (Oriza sativa) is the staple food, estimating glycaemic indices of different varieties of rice is considered important. If the glycaemic index of a specific variety of rice is not known, advice given to patients with diabetes may not be evidence based. The selection of a variety of rice to be consumed by patients with diabetes mellitus should be based on the physiological effect of the rice consumed. The main objective of this study was to determine the glycaemic indices of different varieties of rice in Sri Lanka. Eight varieties of paddy (red/white pericarp) were obtained. Steam parboiling of four varieties were carried out. Dehusking and milling of samples were carried out. Bread was obtained from the Industrial Technology Institute. The Soxhlet extraction of fat, Kjeldhal method for determination of nitrogen content, Juliano's Method for amylase and enzymatic hydrolysis of dietary fiber of rice flour were carried out. Digestible carbohydrate content of rice and bread were determined by enzymatic hydrolysis and Nelson's method. Drying at 100øc to constant weight in an oven for moisture content of rice and bread and the Dean and Stark method for moisture of cooked rice were carried out. Twenty two healthy adults of both sexes aged between 25-50 years employed in a fibre mill in Udugampola-Gampaha district were selected on a volunteer basis among 38 subjects. Informed consent was obtained from subjects and glucose tolerance test was performed to exclude diabetes. Rice and bread portions containing 50g carbohydrates were fed tio22 human subjects following an overnight fast. Fasting blood samples followed by half hourly samples for two hours were drawn. Blood glucose was determined by the glucose oxidase/ peroxidase method using an autoanalyser. The area under the blood glucose curve (AUC) for varieties of rice for each subject was calculated. Average AUC of 3 values for bread was calculated. Glycaemic indices of different varieties of rice were determined. The glycaemic indices of carieties of rice varied between 55-73, and Bg 350 had the lowest glycaemic index. There was no significant difference between glycaemic indices of varieties of white raw and some varieties of red raw rice. The chemical composition of varieties of rice did not show a significant correlation with the glycaemic indices. Parboiling Bg 94 - 1, BW, Bg 351, increased the soluble content. A low glycaemic index was identified in varieties of red parboiled rice (BW 272 6B, Bg 351) and Bg 350. the glycaemic index could not be predicted from the colour of the rice grain nor the chemical composition. Red parboiled varieties and Bg 350 could be recommended for patients with diabetes.
Description
Dissertation: M.Phil., University of Sri Jayawardenepura: USJ(MED), 2000.
Keywords
Carbohydrates
Citation
HETTIARACHCHI, P, The Glycamic indices of different varieties of rice in Sri Lanka, University of Sri Jayawardenepura USJ(MED), 2000: xiv,108P