C. J. Bergman, U.S. Department of Agriculture-Agricultural Research Service, Rice Research Unit, Beaumont, Texas; K. R. Bhattacharya, Rice Research and Development Centre, Mysore, India; K. Ohtsubo, National Food Research Institute, Tsukuba Science City, Ibaraki, Japan
RICE: Chemistry and Technology, Third Edition
The many rice cultivars grown in the world vary greatly in their cooking, sensory, and processing quality. Rice desirable to one group of people or suitable for one product may not be so for another. Chemists began looking into these cultivar differences in rice end-use quality early in the twentieth century. The cultivar difference in rice kernel response to dilute alkali observed by Warth and Darabsett (1914) is probably the earliest recorded research on the subject. Further research was sporadic and was focused by and large on the “cooking” (i.e., hydration property) of rice in India. But the scope of this inquiry was widened to a greater degree in the 1950s. At that time, rice in the United States was categorized into three grain types (long, medium and short), each with precise dimensional and cooking-processing characteristics (Adair et al, 1973). The inadvertent release in the early 1950s of the cultivar Century Patna 231, which had the dimensions of a typical U.S. long-grain rice but different cooking and processing characteristics, came as a surprise and was a financial disaster for the rice industry. This event brought forward the need to understand the basis of rice end-use quality and to devise simple tests for it. What followed was a research effort, coordinated by the United States Department of Agriculture (USDA), that clarified the essentials of rice quality, which remain substantially valid even today. Beachell and Halick (1956, 1957) recorded the first steps of this effort and Beachell and Stansel (1963) its final outcome. Since the 1950s, much research in Germany (Federal Research Center for Cereal and Potato Processing), Spain (Institute of Agronomy and Food Technology), Japan (National Food Research Institute and Niigata University), and especially India (Central Food Technological Research Institute) and the Philippines (International Rice Research Institute) has taken our understanding of rice end-use quality to new levels. And today, research efforts in this arena exist on nearly every continent.
Across the world, rice exists in many combinations of length-width ratio, grain weight, bran color, and endosperm chemical characteristics. The physical form of rice kernels is not associated with their cooking and processing qualities. End-use quality characteristics desired by one region of the world may be completely unacceptable to another. Most rice does not enter the export market but is consumed close to where it was produced. Consequently, consumers are often exposed only to local cultivars and are unaware of the great variation in the physical and chemical characteristics of the world's rice germ plasm. Rice that enters the export market is typically limited to a select few combinations of kernel physical and chemical traits. This facilitates trade by simplifying the language required to identify rice quality-types and is designed to meet the quality requirements of rice-importing nations. For example, rice in the export market that has a long, thin grain typically has a firm, nonsticky cooked texture and is called “long-grain rice.” But, within all of the world's rice germ plasm, that which has a long grain is not always firm cooking and likewise firm-cooking rice does not always exist as a long grain.