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Abstract
This study aimed at evaluating the biological and chemical qualities of some Nigerian rice varieties and identifying the rice quality that will satisfy the various usage of rice by Nigerians for their rice food diets. Twenty three rice varieties were acquired from experimental fields of National Cereal Research Institute (NCRI), International Institute of Tropical Agriculture (IITA) in Ibadan and Badegi. Triplicate (250g) of each sample of parboiled and unparboiled paddy at 12-13% moisture content was dehulled in a laboratory Satake Husker (model: THU) set at 0.8mm milled and polished in 2mins in a Grainman Milling Machine. A laboratory grader disc separator (model: TRG) was used to determine the percentage of whole grain to that of broken rice. Data were collected on percentage milling fractions, thousand kernel weight, grain hardness, length, breadth, and alkali digestibility. Crude protein content was determined in triplicate using the Kjeldahl process outlined in AACC methods based on 16.8% N in rice protein. Amylose content of rice flour was evaluated using Technicon Auto analyzer (model:IN11) and verified using 300-N-Microsample Spectrophotometer. Data were subjected to analysis of variance and the differences among the means were compared by Duncan Multiple Range Test. Significant differences in thousand kernel weight ranged from 24.0g (ITA 212) to 40.8g (IRAT 170). ITA 144 and IRAT 170 had the heaviest kernel and paddy while FARO 27 and ITA 212 had the lightest kernels. It appeared that the heavier the paddy the heavier the kernel. ITA 117 and ITA 131 had the highest rigidity, a characteristic that would offer greater resistance to insect perforation and inhibition of microbial and fungi invasions at storage temperature. Parboiling increased the yields of brown rice, polished and head rice significantly. It ranged from 76.0% (FARO 12 and FARO 29) to 90.4% (ITA 117). Thus parboiling can prevent abrasion and rice breakage.
Crude protein content of parboiled rice flour ranged from 6.0% (ITA 128, ITA 131, TOX 1768, ITA 234) to 9.8% (IRAT 170) making such rice a possible source of protein in the diets of Nigerians. These results indicated that some Nigerian rice possess some qualities found in imported rice. It suggests that for any rice improvement in Nigeria, these biological and chemical attributes and parboiling methods should be considered.
Keywords: Parboiled rice, alkali digestibility, gel consistence, rice kernel hardness, brown rice, head rice.,