R.N.Sayre, research leader, Cereal Product Utilization Research Unit, Western Regional Research Center, ARS, USDA, Albany, CA

Nutrition

The starch in rice is known to lower glucose and insulin levels in the blood - the "glycemic response." Previously all rice was thought to have this beneficial response but scientists have learned that only varieties with a high proportion of amylose (starch) have this property.

A study is in progress to measure amylose content and other molecular properties of the starch in short and long grain varieties to determine their impact on plaque formation in the arteries of rats. Both types of rice produced lower glycemic response in test animals than in a control but the starch in the long grain was more effective at doing so.

With some advanced laboratory techniques, researchers also examined genetic and environmental influences on the molecular size and branching structure of rice starch. Relating information about molecular structure to nutritional and processing characteristics will provide guidance to breeding programs.

Antioxidants and fiber in rice bran also are being investigated for both their effect on circulatory diseases and their possible effect on inhibiting colon cancer.

Technology

Scientists have been developing new techniques for evaluating oxidate off flavors in rice bran. Chromatographic equipment has been obtained to evaluate starch structure. Small animal models and surgical techniques have been developed to evaluate nutritional and health promoting components in rice.

Researchers have also been trying to determine whether processing rice bran and other cereal brans by extrusion cooking would have an impact on cholesterol-lowering properties. They found that processing energy appears to have little effect and that rice bran gave superior results compared to other cereal brans.

Quality Assessment

USDA researchers completed a collaborative study with scientists at the Rice Experiment Station in Biggs to confirm the use of near-infrared (NIR) technology as a valuable tool to measure amylose content and protein in rice. This rapid, nondestructive method allows multiple analyses on single samples.

NIR machines have now been located at the Rice Experiment Station in Biggs and at the Rice Quality Laboratory in Beaumont, Texas. ARS scientists are assisting in developing databases at these locations and in developing spectra measuring amylose or protein in whole grain brown or milled rice directly (without grinding).