Microwave cooking enhances glycaemic potential of rice: An in vitro study

@#Introduction: Rice is the principle staple and energy source for nearly half the world’s population and has significant nutrition and health implications. Most rice varieties are considered high glycaemic index (GI) foods. With rice being a major contributor to the glycaemic load in Asian populations, there is increasing concern of its impact on the development of type 2 diabetes. Devising ways to reduce the glycaemic impact of rice is therefore imperative. Rice is cooked in a variety of ways, such as over an open fire, electric cooker or microwave. We evaluated the impact of the electric cooker and microwave cooking methods on starch digestibility in a variety of rice commonly consumed in Asia. Methods: Nine rice varieties of varying GIs were cooked in an electric cooker and microwave oven, and the starch digestibility of cooked rice measured using an in vitro digestion method. Results: High GI white rice (WR) had reduced starch digestibility after microwave cooking compared to electric cooker (p<0.05). There was a significant reduction in incremental area under the curves (iAUC) and rapidly digestible starch of WR cooked using microwave rather than electric cooker (p<0.05). Interestingly, even for low GI rice varieties such as iddly rice and extra long basmati rice, microwaving increased slowly digestible starch. Conclusion: The results provide indicative data that the glycaemic impact of rice can be reduced when cooked using a microwave oven. These observations have nutritional implications that need to be substantiated using in vivo studies. Microwaving may provide a simple method of reducing the postprandial glycaemia of high GI rice.

Effects of surface proteins and lipids on molecular structure, thermal properties, and enzymatic hydrolysis of rice starch

Abstract Rice starches with different amylose contents were treated with sodium dodecyl sulfate (SDS) to deplete surface proteins and lipids, and the changes in molecular structure, thermal properties, and enzymatic hydrolysis were evaluated. SDS treatment did not significantly change the molecular weight distribution, crystalline structure, short-range ordered degree, and gelatinization properties of starch, but significantly altered the pasting properties and increased the swelling power of starch. The removal of surface proteins and lipids increased the enzymatic hydrolysis and in vitro digestion of starch. The influences of removing surface proteins and lipids from starch on swelling power, pasting properties, and enzymatic hydrolysis were different among the various starches because of the differences in molecular structures of different starch styles. The aforementioned results indicated that removing the surface proteins and lipids from starch did not change the molecular structure but had significant effects on some functional properties.

Amylase Producing Bacillus megaterium T04 Isolated in Rach Lang Stream of Vietnam.

In the study, Bacillus megaterium T04 isolated from Rach Lang stream in Vietnam was identified. The stream samples were diluted in 0.9 % NaCl broth and then spread onto the ISP4 supplemented with rice and wheat starch. The colonies showed the strongest hydrolyzing activity were picked up and identified by biochemical test and 16S rRNA sequencing analysis. The starch hydrolyzing ability of this strain was detected by starch agar plate method. For maximum α-Amylase production, including 174.7 IU/ml and 0.2 IU/ml in medium containing wheat and rice, respectively was obtained after 72 h of incubation. The enzyme still showed high activity in 60% ammonium sulfate that was necessary for study on the enzyme characteristics. As a result, Bacillus megaterium T04 could produce high yield of amylase in simple conditions.