Rice to get rice of good cooking and eating

Rice is the most economically important staple food
crop for a large part of the population, providing two-thirds of the caloric
intake of more than 3 million people in Malaysia. The main rainfed areas are
located in Borneo while the main irrigated areas are located in the Peninsular
Malaysia or the central plain. According to the definition of DOA, the major
rice planting season varies between regions where the main season normally begins
from August to February, while in the offseason, the major rice planting season
starts from March to July of the following year (Department of Agriculture,
2014). There are significant
cultural differences in the determination of rice grain quality and quality preferences.
Quality evaluation of rice involves the application of sensory tests following
method from Matsue and Ogata (1998) and physicochemical determinations by Ohtsubo
et al. (1993) based on the chemical composition, cooking quality,
gelatinization temperature and/or the physical properties of cooked rice. Grain
quality is based on the relative importance of which depends upon the
particular end-use. The most important quality components that are common to
all user, include appearance, cooking, and nutritional quality. Kernel elongation is one
of the major characteristics of fine rice according to Sood et al.
(1979) and is influenced by several physicochemical and genetic factors,
including genotypes, aging temperature, aging time, water uptake, amylose
content and gelatinization temperature (Juliano, 1972). Upon cooking, some
grain varieties can expand more in size than others. For
cooked rice grain quality, greater length elongation, less volume expansion,
and less water absorption have been associated with high-quality rice
varieties, therefore, this trait
largely determines the market acceptability of rice (Tang et al., 1987). Famous rice variety that possessed this
characteristic is Basmati. The consumer’s concern is to get rice of good cooking
and eating qualities, this is largely dependent on the physicochemical
properties of starch which make up 90% of milled rice. Several component traits
like apparent amylose content (AC), gel consistency (GC) and starch
gelatinization temperature (GT) collectively determine cooking and eating
qualities of rice (Ahuja et al., 1995). Previous
results during the past investigation by Unnevehr et al. (1992) also
concluded that cooking quality is directly related to the physical and chemical
characteristics of the starch in the endosperm which are amylose content, gel
consistency and alkali spreading value. Amylose content is one of the major rice traits
that directly related to cooking and eating quality such as texture, flavor,
stickiness, hardness, grain elongation, gel consistency, and gelatinization
temperature of rice variety (Pooni et al., 1993; Adu-Kwarteng et al.,
2003; Asghar et al., 2012) as it consists of linearly linked glucose
molecules and resistance to digestion (Oko et al., 2012). There
are five classes of the amylose content: waxy (0–2%), very low amylose (3–9%),
low amylose (10–19%), intermediate amylose (20–24%) and high amylose (above
24%). Juliano (1971) stated that low amylose content is
associated with cohesive, tender and glossy cooked rice. Meanwhile, high
amylose content is associated with dry, firm, fluffy and well-separated grains
of cooked rice. Lower amylose rice does not become hard and dry when cooked
thus it is preferable compared to the higher amylose rice (above 20%) (Bhonsle
and Sellappan, 2010). Resurrection et al. (1977) indicated that
different temperature during the grain ripening influenced the amylose content
of rice varieties whereby the amylose content generally decreases as the mean
temperature increases. In addition, Paule (1979) said that the amylose content
of rice also influenced by the nitrogen fertilization whereby the value
decreases slightly with nitrogen fertilization but is not affected by the stage
at which nitrogen is applied.