|Rice Quality and Product
ENVIRONMENTAL AND GENETIC INFLUENCES ON HEAD RICE
Rice growers have been concerned about the recent decline in head rice yields. A project was started in 1982 in the Department of Agronomy and Range Science to find out how head rice yields are affected by variety and the environment. The data came from rice delivered by growers to the Rice Growers Association and the Butte County Rice Growers Association from 1979 to 1982.
An analysis of the head rice yields in 1982 on nearly 5,000 lots of rice delivered to the mills showed that the replacement of tall varieties by short-statured varieties did not affect head rice yields. The greatest differences were among maturity groups. From 1979 to 1982, the very early, early, intermediate and late maturing varieties had average head rice yields of 49.4, 54.6, 57.1 and 59.0 percent respectively.
A clear trend toward higher head rice yield with higher grain moisture at harvest was shown for all varieties and all locations. High temperatures during the 10-day period before harvesting decreased head rice yields.
A statistical analysis of all the records indicated that differences in head rice yields among maturity classes could not be explained only by environmental differences during maturity and harvest. There was a strong indication that genetic factors also were involved, suggesting that improvements could be made through the breeding program. Low temperatures prior to flowering did not affect head rice yields but did depress grain yields.
RICE FOOD AND FEED PRODUCT DEVELOPMENT
Since 1970, research has continued toward increasing the consumption of California-grown rice. Earlier studies indicated that consumers in metropolitan areas preferred the appearance, size, and fluffiness of long grain rice over medium grain rice. At that time, there was no long grain production in California, and subsequent research was aimed at developing new food products from medium and short grain types that might have better consumer acceptance.
From 1970 through 1977, the Department of Food Science and Technology at UC Davis developed several products such as high protein canned rice, fermented rice products and various rice flour products. These studies were done cooperatively with the USDA Western Regional Research Center at Albany from 1975 to 1977. Work has continued independently by the Western Regional Research Center from 1978 through 1982. The early interest of food processing companies in new rice products was somewhat disappointing, but their interest is increasing as the research continues.
The Western Regional Research Center has done research on rice bran, rice flour, high protein rice flour, rice sugar syrup and blended nutritional supplements for children. A process has been developed for stabilizing rice bran on a commercial scale. With usual storage conditions, rice bran quickly becomes rancid.
The feed efficiency of stabilized bran showed a 20 percent improvement compared with raw bran when fed to chicks and was equal to raw bran when fed to pigs.
The bran stabilization equipment is being manufactured in California, and a California company is planning to sell stabilized bran as a food ingredient. A Texas company is already selling bran stabilized by this process. The high level of fiber in rice bran and the concern for more fiber in the human diet is helping to promote food sales of stabilized bran. An edible oil can be recovered from the stabilized rice bran.
Rice germ evaluations
Rice germ has been thoroughly evaluated for stability, nutritional and functional properties. It is superior to wheat germ in composition and was well received in consumer tests of breads, cakes, and breakfast cereals containing rice germ. A California company is planning to market rice germ products. A Texas company is researching methods to recover the germ from modern milling operations.
Studies have been completed on the use of rice flour in baked goods and in specific applications where rice flour is preferred to wheat flour. Milling techniques were found to have an important influence on flour performance. Several companies now market rice flour mixes for breads and cakes or market breads and cakes using formulations developed by the Western Regional Research Center. Large new markets have been established for rice flour by at least one California company.
Laboratory and pilot plant experiments have been conducted to convert rice brokens or flour to high protein (25 percent) rice flour and sugar syrup. This is achieved through partial conversion of rice starch to maltose using enzymatic means. The high protein rice flour is expected to be used as an infant food, both domestically and internationally. The sugar syrup can be used as a sweetener or a substrate for yeast cultivation. One large company has an active interest in the process.
A preparation has been developed called Rice-SoyMilk intended for young children as a healthful food supplement. The primary intended use is in developing countries where child malnutrition is a serious problem. Recent work has shown that the nonfat dried milk ingredient in this blended mixture can be omitted and that a rice-soy mix is adequate for the perceived market. English and Chinese companies have started to market analogous mixes in Asia. All of these products are to be discussed at an upcoming international meeting of the Food and Agriculture Organization.
Several processes have been developed to reduce the stickiness of short grain and medium grain rices. Unfortunately, all of these processes cause minor changes in other rice qualities such as color and texture and have not been adopted by industry.