Abstract
Glycaemic index (GI) reflects the blood glucose response after ingestion of a 50 g digestible carbohydrate portion. Many factors affect the GI, including degree of starch gelatinization. The objective was to determine the GI and the effect of different cooking methods on GI of a Pakistani basmati rice (PBR) and an Indian basmati rice (IBR) frequently purchased by Sri Lankans. This was a crossover study. Participants were ten healthy individuals aged 20-30 years whose BMI range was 18.5-23.5 kgm(-2). Proximate composition, [carbohydrate, protein, fat, soluble dietary fibre (SDF), insoluble dietary fibre (IDF) and ash], amylose content and GI of the two rice varieties were determined by using standard methods. Rice was cooked separately in a rice cooker and a microwave by adding 1 cup of rice (110 g) and 1 cup of water (150 ml)). Glucose was used as the standard. GI values were expressed as the average value of 10 participants. Fat, total dietary fibre (TDF), SDF and IDF contents were significantly (p<0.05) higher in IBR when compared to PBR. The GI values of IBR and PBR cooked in a rice cooker (GI=54 SD=8; GI=64 SD=12) or microwave (GI=43 SD=28; GI=56 SD=12) belonged to low and medium GI categories respectively. A percentage reduction in GI values was seen in PBR (12.5%) and IBR (20.4%) when cooked in a microwave oven compared to a rice cooker. Irrespective of the method of cooking PBR had medium GI and IBR had low GI.
Highlights
The Glycaemic index (GI) is defined as ‘‘the incremental area under the blood glucose response curve of a 50 g digestible carbohydrate portion of a test food expressed as a percent of the response to the same amount of carbohydrate from a standard food taken by the same subject’’ [1]
Fat, total dietary fibre (TDF), SDF and IDF contents were significantly (p
The GI values of IBR and PBR cooked in a rice cooker (GI=54 SD=8; GI=64 SD=12) or microwave (GI=43 SD=28; GI=56 SD=12) belonged to low and medium GI categories respectively
Summary
An unstructured interview type market survey was carried out to collect information regarding the consumer purchasing trends and preferences. Portions containing a 50 g digestible carbohydrate of IBR and PBR were 147 g and 151 g respectively. Proximate compositions of the cooked rice of two rice varieties were determined by using standard methods. Amylose and amylopectin contents of two rice varieties were determined by Juliano method [13]. GI of the two rice varieties was determined using a standard method [14]. The test foods (PBR and IBR) and the standard food were served to the same individual on separate occasions. Each subject was served with test food containing 50 g available digestible carbohydrate portions to be consumed within 10-15 minutes with 250 ml drinking water. Approval for the study was obtained from the Ethics Review Committee, Faculty of Medical Sciences, University of Sri Jayewardenepura, Sri Lanka. Informed written consent was obtained from all participants prior to the study
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