Arendt und Zannini - 2013 - Cereal grains for the food and beverage industries

Rice 127
Table 3.6 Range of amino acid composition
(g/16.8 g N) of brown rice and milled rice
Amino acids Brown rice Milled rice
Alanine 5.8 5.6-5.S
Arginine 8.5-10.5 S.6-8.7
Aspartic acid 9.0-9.5 9.1-9.6
Cysteine 1.8- 2.6 1.9-2.1
Glutamic acid 19.9-17.6 18.3-18.5
Glycine 4.7-4.8 4.5^.8
Histidine 2.4-2.6 2.3-2.7
Isoleucine 3.6-4.6 3.7-4.S
Leucine 8.3-S.9 8.4-S.6
Lysine 3.9-4.3 3.4^.2
Methionine 2.3-2.5 2.3-3.0
Phenylalanine 5.0-5.3 5.3-5.5
Proline 4.8-5.1 4.6-5.1
Serine 4.8-S.8 5.3-5.9
Threonine 3.9-4.0 3.7-3.9
Tryptophan 1.3-1.5 1.3-1.8
Tyrosine 3.S-4.6 4.4-5.5
Valine 5.0-6.6 4.9-6.8
Source'. Adapted from Shih (2004).
crystallizing capacities of starch, and increasing the pasting temperature of
the isolated rice starch (Shih, 2004). Additionally, high protein content in
rice causes longer cooking time and firmer structure and is negatively correlated
with reduced smoothness, stickiness, taste and overall palatability
(Mutters and Thompson, 2009).
3.3.2 Lipids
Rice grains contain low levels of lipids (approximately 2.2 % of total grain
weight) when compared to other cereals such as corn (4.9 %),barley (3.4 %),
oats (5.9 %) sorghum (3.9 %) and millet (4.7 %) (Childs, 2004). Only wheat
and rye showed a lower lipid content, having a concentration equal to 1.9
and 1.5 % of total grain weight (data quoted at 14 % moisture), respectively
(Childs, 2004). Fat distribution within the rice caryopsis is not uniform with
lipid being primarily concentrated in the bran fraction and in the embryo
(Table 3.7) (Choudhury and Juliano, 1980; Godber and Juliano, 2004).
Within the endosperm, lipids were unevenly distributed, with the lowest
amount in the centre of the kernel and increasing progressively towards the
outer layer of the endosperm (Normand et al., 1966). Linoleic acid is the
major fatty acid present in brown rice, at an average of 38%, followed in
decreasing amounts by oleic (35 %), and palmitic acid (23%) (Table 3.7).
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