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

SECONDARY PROCESSING 119
than those of the raw flours. Purified β-glucan was extracted from the raw and
extruded flours, and the solubility of these samples was found to differ between
cultivars and extrusion conditions. These researchers also examined the glycosidic
linkage profiles in an attempt to explain solubility differences and were
unable to arrive at a satisfactory conclusion. Baik et al. (2003) extruded break
and reduction flours from two normal starch (nonwaxy) and two waxy starch
barley cultivars. The barley flours were formed into granules before extrusion.
Break stream flours, generally with higher starch content than reduction flours,
produced extrudates with higher expansion indexes. Nonwaxy starch barleys had
higher expansion indexes and lower density values than those of waxy barley.
These researchers concluded that granulation of the barley flour and fine control
of extrusion conditions were essential factors in obtaining an acceptable RTE
breakfast cereal.
The effects of extrusion cooking on the dietary fiber profiles of waxy and
nonwaxy barley flours were reported by Vasanthan et al. (2002). Flour was prepared
by pearling the grain in a laboratory pearler (Satake model TM05, Tokyo,
Japan), removing 30 to 32% of the kernel, followed by pin milling (Alpine Contraplex
wide chamber mill, type A-250, Hosokawa Micron Systems, Summit,
New Jersey). The flours were extruded in a twin-screw extruder (Werner and
Pfleiderer ZSK 57 W 50P, Stuttgart, Germany). The content of soluble dietary
fiber and total dietary fiber increased upon extrusion cooking of both waxy and
nonwaxy barley flours. Changes in insoluble dietary fiber were observed to be
cultivar dependent. Insoluble dietary fiber was increased in the nonwaxy flour
while decreasing slightly in the waxy flour, due to extrusion. It was suggested
that the formation of retrograded amylose caused the formation of some resistant
starch in the nonwaxy flour, thus increasing the level of insoluble dietary
fiber. Increases in soluble dietary fiber in both types of extruded barley products
were thought to be due to the transformation of some insoluble dietary fiber
into soluble dietary fiber and the formation of additional soluble dietary fiber by
transglycosidation.
Through the use of various types of extrusion equipment and techniques along
with select barley cultivars, food products with new and enhanced functional and
nutritional properties may be produced to meet consumer needs and demands.
Extrusion technology that is currently available to the modern food industry can
be used to produce many useful products that are beneficial to the health of
consumers.
Steel Cutting
Steel-cut barley or barley grits are made with rotary granulators or cutters, consisting
of a revolving drum, perforated with round countersunk holes through
which the kernels can flow out after cutting. A series of adjustable knives are
mounted at the lower side of the drum. Depending on the angle of the knives,
which are adjustable, the kernels can be cut into varying sizes. A sifter is used to
remove the fines and, if desired, to classify the cut kernels into specific sizes and