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

SUMMARY 83
showed TKW mean values (and ranges) of 46 (43 to 50) and 39 (36 to 42) for
two rowed (n = 42)andsix-rowed(n = 25) cultivars, respectively. The TKW
of hulless barleys is reduced 15 to 20%, due to removal of the hull.
Volume weight, once commonly called test weight, is now referred to as
hectoliter weight. Regardless of the terminology, it is a measure of density and
is currently expressed as kilograms per hectoliter (kg/hL). Previously, volume
weight was expressed in pounds per bushel. The standard test weight of hulled
barley is 62 kg/hL (48 lb per bushel), but may range from 52 to 72 kg/hL. Hulless
barley volume weights may be as high as 80 kg/hL (Ullrich 2002).
Kernel Uniformity
The uniformity of kernels at harvest increases the ease of malting and processing
for food. Kernels of different sizes vary widely in malting behavior, producing
malts with distinctively different properties (Burger and LaBerge 1985).
Blends of barley having different-size kernels may also present problems in
the pearling process, especially when the barley is only slightly pearled. Edney
et al. (2002) reported that the smaller nature of six-rowed kernels required longer
pearling times than those for two-rowed kernels. However, these authors stated
that there appeared to be no advantage in selecting two- versus six-rowed barley
for pearling, other than the difference in time required for processing. Having
kernels of relatively the same size and shape may be a desirable characteristic for
some processing purposes and may be controlled to some extent by the choice
of barley cultivar or row type.
SUMMARY
The major and minor nutrients in barley are presented in this chapter. Starch
is the largest component, followed by total dietary fiber and protein, respectively.
Starch in most barley is composed of two types, branched chains of
glucose (amylopectin) and comparatively straight chains of glucose (amylose)
in a 3 : 1 ratio, respectively. Barleys that contain mostly amylopectin starch are
called waxy barley, and those that contain more (40 to 70%) amylose starch
are called high-amylose barley. Protein levels are shown to vary widely due
primarily to cultural practices, but there are genotype effects. Protein quality
does not improve with an increased level of protein, which is most often
due to increases in the lysine-poor prolamines. High-lysine cultivars have been
developed but are not widely grown. The lipid content of most barley is relatively
constant, with linoleic acid (18 : 2) being the most abundant fatty acid
present in the triacylglycerols. Starch lipid level is highest in high-amylose barley.
Barley is rich in the fat-soluble vitamin E and contains varying amounts
of the vitamin B complex except vitamin B 12 . Concentrations of the vitamin E
complex, which is composed of eight isomers, have been researched in greater