Protein fractionation and lipoxygenase activity of bran from high yielding rice genotypes
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Date
2018
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Punjab Agricultural University, Ludhiana
Abstract
In the present study, rice bran from 19 genotypes, including ten non-basmati and nine basmati
genotypes were characterized on the basis of their proximate and nutritional composition
along with antioxidant properties of protein fractions. The constitutional level of lipoxygenase
in rice bran was also determined. The content of crude protein, crude fat, crude ash and
dietary fibre in their bran fraction varied from 12.56-22.88 %; 16.92-23.63 %; 8.43-14.96 %
and 21.62-28.48 %, respectively. The mean protein content of various Osborne fractions viz.,
albumin, globulin, glutelin and prolamin among genotypes was found to be in the ratio of
41.09: 18.33: 36.16: 4.42. Significant variation was seen in free amino acids (4.58-10.95),
cysteine (0.91-2.07 mg g-1 DW ), methionine (16.33-27.59 mg g-1 DW), proline (19.48 μg g-1
DW), lysine (3.52-5.86 %) and tryprophan (0.55-1.55 %) content. Antioxidant properties of
rice bran protein fractions in terms of DPPH free radical scavenging activity (%), Ferric
reducing ability power (μmol Fe (II) g-1 DW) and metal chelating power assay(%) was found
in the order of albumin > globulin > glutelins > prolamin. Superoxide anion radical
scavenging activity (%) was found to be highest in albumin fraction, followed by glutelins,
globulins and prolamin. Low reducing power (mg/g DW) and radical cation ABTS.+
scavenging activity (mM/g TEAC) was present in rice bran protein fractions. Wide
differences in the rice bran lipoxygenase activity (0.082-1.81 units) was observed. This
information about the variations in biochemical parameters among rice bran from different
genotypes would enable the breeders’ to produce genotypes with improved bran proximate
composition and ratio of protein fractions with high antioxidant potential and low
lipoxygenase activity for desired end-use.
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