|Rice Utilization and
Project Leader and WRRC Investigators
Robert N. Sayre - Research Leader, USDA-ARS, Western Regional Research Center, Albany, CA
Maura M. Bean
Talwinder S. Kahlon
Richard H. Edwards
Wallace H. Yokoyama
Mei-Chen M. Chiu
Faye I. Chow
Gloria R. Dubuc
Carol A. Hudson
Raymond E. Miller
Jody J. Renner-Nantz
|The focus of this ongoing project, conducted by scientists at
the USDA's Western Regional Research Center in Albany, continues to be on research that
will lead to new rice products for domestic and foreign markets. Toward that end
scientists conduct nutritional analyses, quality assessments and experiment with new
Rice bran is rich in many antioxidants, which have received much attention for their positive effects on human health. Two antioxidants found in rice have shown the ability to reduce blood cholesterol and to reduce the formation of aortic lesions that lead to heart disease. Researchers are continuing to monitor the most abundant antioxidants found in rice for their capacity to fight heart disease.
Part of this work involves studies of hamsters, which have cholesterol levels similar to humans. Researchers say the hamster model is especially sensitive to the effects of rice compounds on blood cholesterol and aortic lesion formation. Last year they developed a surgically implanted "sampling port" for laboratory animals that allows multiple sampling of blood. Preliminary experiments to isolate a portion of the rice bran for use as a dietary fiber source in food formulations are also in progress.
Starch accounts for about 75 percent of the weight of brown rice and is the major contributor to nutritional and textural properties of polished rice. In rice breeding programs, tests such as iodine binding, gelation, gelatinization temperature and amylographic properties are all related to starch structure. These tests measure the average properties of starch and its interaction with moisture and other components in the rice kernel but are usually not sufficient to account for all the variables found in the processing of rice products.
Researchers have been using enzymes and new chromatographic techniques to characterize the molecular structure of rice starch. Multiple-angle laser light scattering detectors are being used to measure the molecular size and shape of starch fractions separated by gel permeation chromatography. Samples from the Rice Experiment Station are being compared to the same varieties grown in other states in order to determine the effects of environmental conditions during grain development. Information on the effects of genetics and environment on starch structure is expected to be useful in evaluating rice breeding programs, providing specifications for rice used in processing and standardizing rice for export markets.
Rice Bran Fiber
The value of rice bran may be increased by separating the non-digestible fiber portion from the digestible carbohydrate, protein and fat fractions. The nutritional fractions could be used as added value food or feed ingredients, while the non-nutritive fiber portion could be processed into a dietary fiber ingredient with health-promoting benefits.
Dietary fiber is insoluble, non-functional and is composed of about 50 percent cellulose and 50 percent hemicellulose. Part of the hemicellulose molecule (if made soluble through processing) can enhance the moisture retention and dietary fiber content of baked goods, so researchers are looking at an enzymatic treatment and extrusion technology to free up hemicellulose from defatted rice bran. As a food additive these fibers would be useful in promoting colonic health.
Researchers have also been experimenting with extrusion technology to produce expanded and roasted snack items from rice bran in combination with other grain and legume fractions. They describe the products as having a pleasant, nutty flavor that may be substituted for nuts in snacks and cereal products.
Researchers have been using Near Infrared Reflectance Spectroscopy (NIR) equipment to test large numbers of rice samples from breeding programs at both the Rice Experiment Station near Biggs and the Rice Quality Laboratory in Beaumont, Texas. This nondestructive technology measures amylose content and protein and is expected to increase in importance for assessing the quality and characteristics of rice. It may be required for export specifications in the future.