Cereals processing technology

Rice production 81
evaluating quality characteristics of new varieties over wide ranges of
environmental influences such as soil, climate and cultural practices.
Characteristics influencing qualities in rice include: (a) hull and pericarp
color; (b) grain shape, size, weight, uniformity, and general appearance; (c)
milling outturn; (d) kernel chalkiness, translucency and color; and (e) cooking,
eating and processing characteristics.
5.2.1 Interrelationships of variety, grain type and quality
Traditionally, rice varieties in the United States are classed as long-, medium-,
and short-grain types. More than 99% of the US crop is produced from varieties
developed by public rice research centers and experiment stations located at
Stuttgart Arkansas, Briggs California, Crowley Louisiana, Stoneville Mississippi
and Beaumont Texas. These centers are operated and supported by the five state
agricultural experiment stations, the USDA-ARS, and local producer organizations.
Through planned breeding, varieties of each grain type are associated with
specific cooking, eating, and processing qualities. High-quality conventional US
long-grain varieties cook dry and fluffy, with cooked grains tending to remain
separate, whereas cooked kernels of conventional medium- and short-grain
varieties are moist and chewy, with grains tending to cling together. All three
grain types, with their characteristic cooked textural qualities, are needed for
both domestic and foreign trade. In the US, the long-grain types account for over
60% of the total production, medium-grain types less than 30%, and short-grain
types the remainder. 7
In many rice products, qualities and grain types of conventional long-grain
varieties are preferred; in others, short- and medium-grains, with their
characteristic textural properties, are required. It is essential that new varieties of
each grain type have the same or improved milling and cooking qualities as the
varieties they replace. Although thousands of rice varieties exist worldwide, only a
few (usually less than a dozen) varieties are grown commercially in the United
States in any one crop year. Generally, these consist of four or five long-grain, four
or five medium-grain, and one or two short-grain varieties, which are continually
replaced by new, improved varieties developed in public breeding programs.
Scented (aromatic) long-grain rice is produced in small acreages as specialty
products. This rice gives off an aroma similar to that of roasted nuts and has a
flavorful nutty taste. A major constituent responsible for the unique flavor of this
type of rice is 2-acetyl-1-pyrroline, present in the volatile oil fraction. Two
aromatic rices are in limited production: (a) Della types, characterized as
intermediate-amylose/intermediate-gelatinization-temperature types that cook
dry, fluffy, and separate like conventional US long-grains; and (b) Jasmine
types, which are low-amylose/low-gelatinization-temperature types and cook
soft, moist, and clingy like imported fragrant rices from Thailand. A third type is
the so-called Toro-type rice. This rice has the grain size and shape of US longgrains
but possesses the cooking and eating behaviors of US short- and mediumgrain
types.