THESIS

ice due to the various cooking and cooling combinations under test ranged from 0.6 g
to 5.1 g/100 g DM. Decreasing the rice : water ratio (1:2) and cooling (24 hr at 4 o C)
after cooking significantly increased the RS content. Extrusion decreased the RS
content in the high RS rice only (0.42 – 0.16 g/100 g).
2.8 Glycemic index of rice starch
The glycemic index (GI) is a physiological concept used to classify
carbohydrate containing foods. It is closely tied in with the term ‘glycaemic
response’. Both refer to the ability of a particular food to elevate postprandial blood
glucose concentrations. GI is measured as the incremental area under the blood
glucose curve after consumption of 50 g of available carbohydrate from a test food,
divided by the area under the curve after eating a similar amount of available
carbohydrate in a control food (generally white bread or glucose) (Ludwig and Eckel,
2002). Foods with high GI value release glucose rapidly into the blood stream (elicit a
rapid glycaemic response), while foods with a low GI value release glucose more
slowly into the bloodstream and result in improved glycaemic and insulinaemic
responses.
Waxy and low-amylose rice had higher glycaemic indices than
intermediate- and high-amylose rice (Goddard and Marcus, 1984; Juliano and
Goddard, 1986; Jiraratsatit et al. 1987; Tanchoco et al. 1990), (Table 4). Processing,
such as parboiling and noodle-making, tends to reduce the glycaemic index of rice,
particularly which of high- and intermediate-amylose rice (Panlasigui, 1989; Wolever
et al. 1986). By contrast, Tsai et al. (1990) reported that waxy rice, rice gruel,
steamed rice and rice noodles had similar glycaemic indices to that of white bread in
NIDDM patients. Among high-amylose rice, the low-GT, hard-gel IR42 had a higher
glycaemic index than the intermediate-GT, softer-gel IR36 and IR62 (Panlasigui,
1989). By contrast, Srinivasa Rao (1970) reported that the ingestion of hard-gel IR8
resulted in a lower peak plasma glucose level than ingestion of the softer-gel both
have high amylose and low GT.
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