Assam, situated at the North East part of India is particularly
rich in rice germplasm. Assam is considered as one of the origins for rice and
has got wide collection of rice cultivars. In Assam, the high amylose content
rice varieties are consumed as staple food, and the waxy (0-8% amylose) and the
intermediate amylose containing varieties are processed to make speciality
products. The chakua rice is
characterized by its semi glutinous character with amylose ranging from 12-17% 1.
This is a class of rice used for instant preparations. Similar class of rice is
not known in other parts of the world. Its preparations are very popular in
community feasts and festivals in Assam. ‘Komol chaol’ (soft rice) are prepared
from this class of rice. This rice is very common and popular in rural Assam. Traditionally, chakua grains are soaked in water at room temperature
for 3–4 days to attain an acceptable moisture level. The excess water is
drained, and the grains are put in freshwater and cooked over wood fire till
the husks start splitting. The water is again drained and the grains dried
under the sun on the same day. Dried grains are milled in a ‘dheki,’ the
traditional foot pounding machine to get the ‘Komal chaul'(soft rice) product.
Drying of the boiled grains is done on the same day, so that the milled product
attains soft texture on simple soaking in water at room temperature.
preparation can be preserved for quite long time and can be consumed instantly
by soaking the rice either in cold or hot water for a brief period of time and
then consumed with sugar or molasses, milk or curd and even with salts and oils
and pickles. Rice powders and flake rice prepared from chakua rice are
very tasty and preferred by the local people of the area. These preparations
seem to be useful for sailors, travelers, mountaineers, defense personal, etc.
However, not much research has been done so far to know its nutritional
composition. Considering paucity of work
related to nutritional profile of this group of rice of Assam, India the
present study was selected.
Seventeen varieties of chakua rice were collected from the Regional Agricultural Research
Station, Assam Agricultural University, Titabor, Assam, India. The brown form
of all the collected rice varieties was analyzed for proximate composition,
amylose content and mineral content. All the chemicals used for biochemical
analysis were of analytical grade.
Determination of moisture content: The moisture content was determined by moisture meter (MA
35, Sartorius AG Germany).
Determination of proximate composition: Standard methods 2 were followed to determine the
proximate composition (total ash, crude fat, crude protein and crude fibre).The
carbohydrate content (% dry basis) was estimated by subtracting the
percent values (on dry weight basis) of
crude protein, crude fat, crude fibre and total ash from 100.
food energy: The gross food energy was estimated 3
using the equation:
energy (kCal/100g) = (CP × 4) + (F × 9) + (CHO × 4), CP
means crude protein (%); F
crude fat (%); and CHO means carbohydrate content (%).
of amylose: The amylose was
determined by the method of Sowbhagya and Bhattacharya 4.
Determination of mineral content: Standard methods were followed to determine the
minerals. The phosphorus and iron were estimated by spectrophotometric method 5,6,
respectively and potassium and sodium were estimated with flame photometer.
RESULT AND DISCUSSION
Proximate composition: Proximate composition of brown
rice of chakua varieties of Assam are presented in Table 1.
Moisture content: The percentage of moisture is
an important factor for storing, processing and marketing quality of the rice.
The moisture content is dependent upon many factors such as variety of rice,
yield, proportionate amount of chemical constituents of the grains, processing,
environmental factors, etc. In the present observation, the moisture content of the brown rice varieties were found
to vary from 10.1 % for ‘Maju chakua -2’ to 11.8 % for ‘Kagoli chakua’ on fresh
weight basis. However, the moisture content of all the varieties was
found within safe level of moisture for storage. Around
12% moisture is recommended for long term storage to avoid insect infestation
and microbial growth 7,8. The moisture content of high
amylose content rice varieties of Assam like Ranjit, Kala chakua, Aguni bora and Bhogali bora were reported to be 13.1%, 12.9%, 13.1% and 13.2%,
Total Carbohydrate content: Rice
carbohydrates are mainly starch which is composed of amylose and amylopectin. The
total carbohydrate was found to be in the range of 69.30% in ‘Nepali chakua’ to
85.90% in ‘Lahi chakua’. The total carbohydrate content of nine milled rice varieties
of China were reported to be in the range between 87.2%-92.5% 10. Our
findings on total carbohydrate content was found to be similar with those
reported earlier for aromatic rice verities of India (75.87-82.70%) 11 and
some rice varieties of Malayasia (67.48-77.51%) 12.
Crude fibre content: The
crude fibre is not a significant component for rice. The crude fibre content on
dry weight basis was found to be the lowest (0.30%) in ‘Kagoli chakua’ and the
highest in ‘Maju chakua-2’ (1.65%). The crude fibre detected in the present
study (0.30% to 1.65%) was found to be similar to those reported earlier 13,14.
However, the crude fibre content of aromatic rice ranged between 0.48- 0.85%
and non aromatic rice ranged between 0.64-0.65% 11.
Crude protein content: Protein
content influences the nutritional quality of rice 15. Rice protein content
comprises up to 8% of the grain 16, which is low but of high nutritional
value 17,18. Earlier, the protein content up to 15% in different rice
varieties are being reported 19,20. The protein content of more than 10% for
rice is classified as high protein content 21. In the present study too, in six chakua varieties, the protein content of brown rice was more than
10%. However, the crude protein content of aromatic rice varieties ranged
between 7.23-9.51% and the non-aromatic varieties ranged from 6.87% to 7.09%
11.The crude protein content of brown rice of some varieties of Malayasia and
Pakistan were reported to be 9.50-9.83% 12 and 7.50-9.16% 22, respectively.
Crude fat content: Crude fat
content influences the taste of cooked rice, because rice with high fat content
tends to be tastier and have less starch 23. Among the chakua varieties, the crude fat was
found to be the highest (8.20%) for ‘Sam chakua’ and the lowest for ‘Malbhog chakua’
(not detected). Earlier, the crude fat content for brown rice
of some varieties from Malayasia were reported to be in the range of 5.85-8.9% 12.
However, the crude fat content of milled form of rice varieties from India and
Pakistan were reported to be less than 1% 11 and 1.92-2.70% 22.
Ash content: Ash content plays an
important role to reflect the mineral elements of a food sample 24,25. It
gives an idea to determine the levels of essential minerals present in the food
26.The ash content of chakua rice varieties was found to vary from 0.66% for ‘Boka Chakua
-1’ to 1.52% for ‘Lahi Chakua’. The ash content of brown rice of chakua varieties were found to be lower than
those reported earlier for some brown form of rice varieties from Malayasia
(1.67-1.83%) 12. However, the ash content for some aromatic rice varieties of
India and Pakistan were reported to be in the range of 0.38%-0.73% and
1.48%-1.98%, respectively 11, 22.
Energy content: Among
the chakua varieties, the energy
value was found to be the highest (389.16 kCal/100g) for ‘Nepali chakua’ and
the lowest for ‘Bora chakua’ (349.84 kCal/100g) (Table 1). Higher
energy content of some of the chakua varieties
might be attributed to their brown form, as most of the crude fat is retained
on the outer layer of rice grain. Earlier, the energy content for aromatic rice
varieties of India and brown rice of Malayasia were reported to be
348.79-365.23kCal/100g and 372.53-388.02kCal/100g, respectively 11,12.
Amylose content: Amylose
content of rice grain is considered to be one of the most important
compositional indices of rice cooking and processing behavior. The varieties
having very low amylose (<2 to 9%) content are sticky, moist and tender when cooked. On the other hand, the varieties having a high content of amylose (>27%) become very hard when cooked. As such, the 20-25% amylose containing
varieties, which on cooking remain fluffy and soft, are mostly preferred over
other varieties. Amylose is almost absent from the waxy (glutinous) rice. Such
rice does not expand in volume, are glossy and sticky and remain firm when
cooked. Intermediate amylose content is preferred by the major world rice
In the present
study, the amylose was detected in the range of 9.12% in ‘Bor chakua’ to 16.02%
in ‘Lahi chakua'(Table 2). From the earlier studies on parboiled rice of Assam
like Ranjit, Kala chakua, Agoni bora
and Bhogali bora 27, it was concluded that the amylose content to be 27.2%, 12.6% for Ranjit, Kala chakua, respectively and the same for Aguni bora and Bhogali bora was 1.1%. Earlier, the amylose content of some rice
varieties of Malayasia was reported to be 12.50-25.70% 12.
Mineral content: Some of the important mineral content of chakua rice varieties are presented at the Table 3. The phosphorus content of chakua rice varieties of Assam ranged from 173.95mg/100g (Lahi Chakua) to 328.78mg (Pozo Chakua),
with an average value of 242.95 mg/100g.
However, the phosphorus content of rice were reported to be higher
(0.50-0.55% or 500-550mg/100g) 28.
In the present study, the potassium content varied from
84.71mg/100g (Bor chakua) to 287.6mg/100g (Bora chakua), with an average value
of 180.59 mg/100g. Earlier, the potassium content of rice were reported to be 0.15-0.23% or 150-230mg/100g 28, 237.8-279.1mg/100g 22
and 50-265mg/100g 11.
The sodium content varied from 14.82mg/100g (Bor Chakua) to
22.70mg/100g (Lahi chakua), with an average of 19.67mg/100g. The sodium
composition of 20 rice varieties of Nigeria ranged from 0.09 – 0.17 % or
90-170mg/100g 28. However, the sodium content for some rice varieties of
Pakistan varied from 8.9-10.9mg/100g 22 and for some aromatic rice varieties
of India, it varied from 4.14-6.88mg/100g 11.
The iron content of the brown form of chakua rice varieties varied from 1.04mg/100g in ‘Maju chakua-1’ to
643.50mg/100g in ‘Kagoli chakua’, with an average of 44.68 mg/100g. In the
present study, the iron content of two chakua
varieties in brown form were found to be higher than the already reported
values, 0.24-3.15mg/100g 11, and 18.6-31.7mg/100g 22, for some rice varieties of India and Pakistan. The iron
content of two chakua rice varieties
‘Kagoli chakua’ and ‘Saru chakua’ were found to be remarkably higher, 643mg per
100g (almost 50% of total minerals) and 44.97mg per 100g, respectively. The
highly intense colour of the brown form
of this variety justifies the vernacular name of the variety ‘Kagoli chakua’, which means red colour. Detection
of high iron containing rice varieties may lead to utilization of this
prominent variety in future rice breeding program. However,
in earlier studies involving high iron containing rice varieties, the iron content
of seed was found to be 15.7 µg/g (1.57mg/100g) in rice (Oryza sativa L. subspecies indica) cv. IR68144 29. In a recently
conducted experiment to develop high iron containing rice at International Rice
Research Institute, Phillipines the average iron content of the milled rice of developed lines was
found to be 1.2-1.5 mg/100g 30.
The present study reveals a significant finding regarding iron
content of rice. The iron content varied from 1.04mg/100g in ‘Maju chakua-1’ to
643.50mg/100g in ‘Kagoli chakua’, with an average of 40.49mg/100g. The amylose
content of chakua rice was found to be of intermediate type.