Rice proteins and essential amino acids

Cereals are crops grown in the largest quantities and the most important crops for human consumption. In 2014, the sum of the grain yields of the three major cereal crops (maize, wheat, and rice) was 2.5 billion tons, constituting approximately 90% of the total global production of cereals in that year (http://www.fao.org/faostat/). The yield of these crops is much larger than the yields of the major legume crops (soybean and pea; 318 million tons total). Rice seed protein is an important source of nutrition and energy for 50% of the world's population, for whom rice has long been a staple diet. The protein content of rice, at approximately 7%, is relatively low compared with that of other cereal grains. However, because of the huge quantity of rice produced worldwide (approximately 741 million tons annually), a considerable amount of rice protein is potentially available. In this chapter, we update information on the chemistry and technology of rice proteins described in the previous versions (Juliano, 1972, 1985; Shih, 2004). We focus on the accumulation of rice seed storage proteins (SSPs) and improvement of their essential amino acid composition. In addition, we review recent studies of the seed biology of other cereals, which may be useful for improving the essential amino acid content of rice protein.