Barley for Food and Health: Science, Technology, and Products

GENETICS AND NUTRIENT COMPOSITION 77
TABLE 4.5 B-Complex Vitamins (mg/kg) in Barley, Dry
Matter Basis
n Means Range
Thiamine 4 5.2 4.0–6.5
Riboflavin 5 1.8 1.2–2.9
Nicotinic acid 4 63.3 46.0–80.0
Pantothenic acid 4 5.1 2.8–8.0
Biotin 2 0.14 0.13–0.15
Folic acid 3 0.43 0.2–0.7
Pyridoxine 3 3.5 3.0–4.4
Choline 2 1290 920–2200
Sources: Hopkins et al. (1948); Briggs (1978); National Research Council
(1984); Kent and Evers (1994); Köksel et al. (1999); USDA (2005).
B-complex vitamins in barley, although it is 85 to 90% biologically unavailable.
Extrapolation from research with wheat bran indicates that nicotinic acid is incorporated
in a number of polysaccharide and glycopeptide macromolecules that do
not release the vitamin unless treated with alkali or acid (Mason et al. 1973;
Carter and Carpenter 1982). Barley contains significant amounts of tryptophan,
from which nicotinic acid may be synthesized by animals, although approximately
50 mol of tryptophan is required to produce 1 mol of nicotinic acid.
Variation in the content of B-complex vitamins from one cereal grain to another
is quite small except for nicotinic acid, which is much higher in barley, wheat,
sorghum, and rice than oats, rye, maize, and millet. Barley contains the highest
level of nicotinic acid of all the cereals. Extrapolating from wheat data,
the B-complex vitamins are concentrated in various parts of the barley kernel.
Thiamine is concentrated primarily in the scutellum (62%) and aleurone layer
(32%). Almost equal amounts of riboflavin found in the aleurone layer (37%)
and endosperm (32%), with smaller amounts occurring in the embryonic axis
(12%) and scutellum (14%). Nicotinic acid is concentrated in the aleurone layer
(61%), with smaller amounts in the pericarp (12%). Pyridoxine is also concentrated
in the aleurone layer (61%), with smaller amounts in the pericarp (12%)
and scutellum (12%). Pantothenic acid is concentrated in the aleurone layer (41%)
and endosperm (43%) (Kent and Evers 1994).
Minerals
The gross mineral matter of barley is the “ash” remaining after burning a sample
until it is free of carbon. Thus, minerals are often referred to as “inorganic”
nutrients. The ash content of typical barley ranges from 2.0 to 3.0%, with hulless
types being on the lower end and hulled types on the upper end of the
range. Barley hulls contain around 6.0% ash (Kent and Evers 1994), which is
60 to 70% nutritionally inert silicon occurring primarily in the outer lemma (Liu
and Pomeranz 1975; Pomeranz 1982). At least 14 mineral elements shown to
be nutritionally important occur in varying amounts in whole-grain barley. The