Abstract:
Rice is the staple food of Sri Lanka and can be used effectively to increase the health
status of our community. Diabetes is one of the major health issues facing Sri Lankans
today. Glycemic Index can be defined as the blood glucose response of a particular food
compared to a standard and, moreover, it is important for diabetic people in planning
their diets. As the staple food, it is important to identify the Glycemic Index and related
functional properties of available rice varieties to enhance the health status of our
community.
The objective of the study was tp; determine the amylose content, dietary fiber content
and Glycemic Index of selected rice varieties grown in Sri Lanka. Ten rice varieties,
both traditional and improved, were used for the study. Amylose content and dietary
fiber contents were determined using simple iodine colorimetric method and enzymatic
gravimetric method, respectively, for both polished and unpolished rice samples.
Proximate composition of ten rice varieties and white bread was determined and the
available carbohydrate content was calculated, Glycemic response for eight unpolished
rice varieties, four polished rice varieties and white bread was determined using in-vitro
digestibility method.
Amylose content of unpolished rice varieties ranged from 29.4% (Dik wee) to 25.7%
(Sulai) and in polished rice varieties ranged from 29.4% (Bg 359) to 25.9% (Dik wee)
having the highest and the lowest values. Dietary fiber contents of unpolished varieties
ranged from 4.3% (Sulai) to 2.5% (Bg3-52) and in polished varieties ranged from 3.1%
(Kalu heenati) to 0.1% (Kalu heenati) having the highest and lowest values. Glycemic
Index of unpolished rice varieties ranged from 108.50% (Bg 359) to 61.81% (Sulai) and
in polished varieties ranged from 70.56% (Sulai) to 64 (Rath suwadal) having the
highest and lowest values.
There was a significant difference (P<0.05) of amylose content among unpolished rice
varieties as well as polished Varieties. But, there was no significant difference (P>0.05)
in amylose content between polished and unpolished varieties. There was a negative
correlation between dietary fiber content and Glycemic Index, but there was no
correlation between amylose content and Glycemic Index. Therefore, amylose content
alone may not be a good predictor of Glycemic Index and there may be other factors
influencing the Glycemic Index of rice. Moreover, particle size of cooked rice and
polishing rate appeared to have an impact on Glycemic Index.