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

SPECIAL AND MISCELLANEOUS PROCESSES 125
they are different and each product possesses different functional characteristics
(Jadhav et al. 1998).
SPECIAL AND MISCELLANEOUS PROCESSES
The location of various nutrients in the barley kernel permits the concentration
and semi-isolation of a number of these important nutritional compounds
by taking advantage of standard grain processing procedures. Products that contain
concentrated levels of various nutrients are produced in pearling and roller
milling. For example, phenolic compounds are located in the outer areas of the
kernel and are concentrated in the pearlings in the process of making pearl barley
(Lampi et al. 2004) and in roller-milling fractions (Andersson et al. 2003). Barley
pearlings also contain concentrated levels of other nutrients, such as oil and
vitamin E (Wang et al. 1993; Peterson 1994; Marconi et al. 2000). Air classification
and sieving are effective methods of producing fractions of ground barley
having enhanced levels of different components, primarily protein and β-glucan.
Concentration, isolation, and purification of barley β-glucans received considerable
attention even before the official recognition by the FDA (2006) of health
benefits of β-glucans relating to control and prevention of cardiovascular disease
in humans (Klopenstein and Hoseney 1987; Goering and Eslick 1989; Bhatty
1992, 1993a, 1993b; Wu et al. 1994; Knuckles and Chiu 1995; Sundberg et al.
1995; Vasanthan and Bhatty 1995; Andersson et al. 2000). These studies utilized
standard dry-milling processing, such as pearling, roller milling, sieving, and
air classification, to concentrate the β-glucans. In roller milling and pearling, the
outer seed coat is separated from the endosperm, producing products that are representative
of the two areas of the kernel that may be refined by air classification
and sieving. Air classification separates finely ground grain into small, medium,
and large fractions having different particle sizes which differ in nutrient content.
Further air classification and/or sieving of each fraction can produce even
greater concentrations of specific nutrients. Dietary fiber is associated with larger
particles, while the small particles contain higher levels of starch and protein.
Solvent extraction procedures have been researched that produce products with
increased levels (70 to 80%) of β-glucan (Goering and Eslick 1989; Bhatty 1993c;
Burkas and Temelli 2004). More recently, a relatively pure high-β-glucan (about
70%) product has been produced on a commercial scale from waxy hulless barley
for the purpose of supplementing numerous food products (L. Kolberg, personal
communication, 2006). A β-glucan concentrate purified from barley fiber with
nearly 90% purity was recently reported to have been developed (Zhang et al.
2007).
Linko et al. (1983) and Goering and Eslick (1989) developed processes for the
concentration of maltose, producing high-maltose syrup from barley. The patented
process of Goering and Eslick (1989) included the production of barley β-glucan
concentrate, bran protein, and oil in addition to high-maltose syrup. Cowan and
Mollgaard (1988) developed a procedure to prepare hydrolyzed β-glucan that