Rice Utilization and
Product Development-99



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Project Leader and Principal UC Investigators

Wallace H. Yokoyama, research chemist, USDA Western Regional Research Center, Albany

Charles F. Shoemaker, professor, Dept. of Food Science and Technology, UC Davis

Much of the groundwork for new rice products in domestic and foreign markets is laid at the USDA’s Western Regional Research Center in Albany. In 1999 food scientists there and at UC Davis continued exploring the textural properties of rice and the antioxidant and cancer-fighting properties of rice bran.

bowlrice.jpg (7631 bytes)Rice Starch Evaluation

Waxy rice types vary in cooking properties that are important to high speed food processing methods.   For instance, waxy rice flours in breakfast cereals and other baked goods add crispness (but not hardness) to the final product.    Scientists evaluated six samples for a wide range of cooking properties —  viscosity and gelatinization, hardness, stickiness, stringiness, toughness, adhesiveness and starch molecular weight.  Researchers determined that the samples fall into one of two classes. 

California waxy rice tested more like waxy rice from China and Thailand than waxy rice from Japan.   The divergent cooking properties of waxy rice may be due to differences in the molecular weight of the amylopectin form of starch.   Based on this study, researchers are confident the potential exists for new waxy California rice to become more similar to Japanese waxy rice.

Preliminary studies were also begun to evaluate rice starch quality in fluid food products such as baby foods where rice starch is used as a thickening agent, as well as a hypoallergenic source of food energy.  Results suggest that true amylose content varies considerably due to environmental factors, creating undesirable variation in processed products.

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Rice Bran Nutrition

Rice has a healthful image and research has demonstrated that particular components of rice can help reduce risk factors associated with heart disease and colon cancer.   Studies of the health-promoting properties of rice and rice fractions are helping this image.

Research on the cholesterol-lowering properties of rice bran has produced mixed results.   Some studies indicate that rice bran and/or rice bran oil reduce plasma cholesterol in test animals while others have shown no effect.  Scientists believe a greater understanding of the physical form of rice bran phytosterols would help clear up the confusion. 

The oryzanol found in rice may be as good or better than other, similar plant compounds currently used in margarines to reduce cholesterol.

Oryzanols, a mixture of three different phytosterols have been the main focus of research into the cholesterol-lowering properties of rice.  Researchers developed an animal model using hamsters that led to the successful lowering of plasma cholesterol.   In this study oryzanol decreased low density lipoprotein (LDL) or "bad" cholesterol by 24 percent when fed at levels consumed by humans.  Furthermore, the LDL/HDL cholesterol ratio improved 37 percent. 

This study indicates that under the proper conditions, the oryzanol found in rice may be as good or better than other, similar plant compounds currently used in margarines to reduce cholesterol.

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