Knowledge about rice

Rice  botany

Rice is a cereal crop – a member of the grass family, Graminae. This family is divided into a number of genera (subfamilies), one of which is Oryza. This genus is further divided into a number of sections. One of them is sativae. There is a further subdivision called series. The rice grown in Asia is of a series sativa and its botanical name is Oryzasativa

Family: Graminae; Genus: Oryza; Section: sativae; Series: sativa.

Three most common sub-series of Oryza sativa are Japonica, Javanica and Indica.

Japonica is found in a more moderate climate of Japan and Korea. It is mostly grown and consumed domestically. It can be determined by it relatively shorter plant length and short, roundly rice grains. When cooked, its grains are moist and slightly sticky.

Javanica, one with a larger grain, is commonly found in Indonesia and the Philippines. Due to their low productivity, the cultivation of Javanica is limited to the place they were first discovered.

Indica likes warm, semi-tropical and tropical climate. It is the majority of rice that is grown in the other parts of Asia including India where they were first seen. Later some varieties of Indica rice were brought to America for the purpose of large scale farm production. Typical varieties of Indica rice are Thai HomMali rice (Jasmine), Basmati and most other slender long-grained varieties. So we can say that Indica is the world’s staple food.

Other two common series are Oryzaglaberrima and Oryzaofficinalis. The former is grown in Africa as human food while the latter are wild rice.

There are also a number of other series such as Oryzaspontanea, Oryzaperennis and Oryza from which Oryza Sativa, the world’s most widespread series, is believed to evolve. These, however, are of interest only to the botanists.

Structure of rice grain

The complete hull consists of a lemma, a palea, an awn (tail), a rachilla (grain stem) and two sterile lemmas. Once grinded with light force, the husk easily breaks itself apart from the inner caryopsis. The husk is inedible but makes up approximately 20-25% of the total grain weight depending on the variety.

  • The caryopsis (brown rice) consists of three fibrous bran tissues- pericarp (or fruit coat), tegmen (seed coat) and aleurone- and endosperm (hard dough) and embryo.
  • Pericarp consists of three fibrous layers of protein, cellulose and hemicellulose.
  • Tegmen is next and inner to the pericarp. It consists of two-piled tissues with arrays of fatty material.
  • Aleurone is next and inner to the tegmen. It envelops the starchy endosperm and the embryo. Aleurone tissue contains high protein and partially oil, cellulose and hemicellulose.
  • Endosperm, the largest portion of the rice grain, is developed from pollination of nucleus of the pollen grain and polar nuclei of the pistil. Its starchy content comprises of mostly complex carbohydrates and some proteins.
  • Embryo, the reproductive organ of the grain, is one of the two products of the “double fertilization process”- one where nucleus of the pollen grain reaches one of the egg cells in the pistil. Embryo is rich in protein and fat.

From rice grains to white rice

When rice grains turn golden-brown from green, it is ripe and the plant is ready for cutting. After the cutting, the rice is threshed to separate the grains from the rest of the plant and then winnowed. Winnowing takes the chaff away from rough rice (complete grains with hulls intact). Then rough rice is fed through a sheller to remove the husk to get brown rice. If brown rice is further milled to remove bran layers on the kernel, white rice is obtained.