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

74 BARLEY: GENETICS AND NUTRIENT COMPOSITION
starch is reported to contain about 7.0% total lipid (Hofer 1985; Åman and
Newman 1986). Some reports suggest that the genetic factors controlling waxy
and high-amylose starch in barley may be linked to genetic factors that increase
levels of total lipids. Xue et al. (1997) reported a 25% increase in total extractable
lipids in waxy compared to nonwaxy isotypes in Compana and Betzes isotypes
(n = 18). Glacier Ac38, a high-amylose selection from the cultivar Glacier, is
reported to contain over 30% more total lipid than is contained by Glacier (2.3
vs. 3.0%). Hulless high-amylose Glacier developed in a backcrossing selection
study at Montana State University was reported to contain 2.9% total lipid, thus
retaining a major portion of the increased lipid in the original high-amylose
cultivar, Glacier Ac38 (Xue 1992). Although there appears to be a linkage in
increased lipids with high-lysine and starch type, caution should be exercised in
interpreting these data without more complete testing and evaluation of larger
samples grown in diverse environments.
An important group of nutrients, associated with barley lipids due to their
solubility in lipid solvents, are the tocopherols and tocotrienols. This group,
collectively called tocols or vitamin E complex, is discussed in the following
section.
Vitamins
Vitamins are organic compounds required in small amounts for the maintenance
of normal biochemical and physiological functions of a mammalian system. These
compounds are essential components of a diet, and if absent for a period of time,
deficiency symptoms are manifested in various ways. Vitamins are referred to
as accessory food factors, and as such, they are considered essential nutrients
in that they cannot be synthesized in amounts sufficient to meet the needs of a
system. The vitamin theory was initiated in the early part of the twentieth century
(Funk 1911, cited by Oser 1965) and the term vitamine was coined by Funk. The
terminal “e” was dropped from the spelling, as subsequent research showed that
compounds fitting the definition of accessory food factors were not all amines.
The term vitamin has been retained in its generic rather than its chemical sense
and presently is used as a name for accessory food factors that are neither amino
acids nor inorganic elements.
The vitamins were originally named according to their function, their location,
the order in which they were discovered, and in combinations. Over time, at least
68 different accessory food factors were proposed, but only 15 compounds are
officially recognized as true vitamins at the present time (Berdanier 2002). The
vitamins are divided into classes based on solubility in lipid solvents or water.
The lipid-soluble vitamins are A, D, E, and K; the water-soluble vitamins are
thiamine (B 1) , riboflavin (B 2 ) nicotinic acid (B 3 ) , pyridoxine (B 6 ), cobalamine
(B 12 ), biotin, pantothenic acid, folic acid, ascorbic acid (vitamin C), choline, and
myoinositol. Other than vitamin C and myoinositol, the water-soluble vitamins
are often referred to as the B-complex vitamins. Since some synthesis of choline
occurs in animals, it does not strictly adhere to the definition of an accessory
food factor and is thus not always considered a vitamin.