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

122 BARLEY PROCESSING: METHODS AND PRODUCT COMPOSITION
inactivated the peroxidase enzyme, which is indicative of destroying the activity
of several enzymes in grain that reduce shelf life and the nutritional quality of
flour and by-products. Infrared treatment also had a positive effect on how barley
kernels fractionated during milling, resulting in increased yields of straight-grade
flour. Roller milling yields of straight-grade flour were increased from 38% for
untreated barley to 42, 43, and 46% at moisture conditioning levels of 16, 20, and
24%, respectively. Additionally, β-glucan and TDF levels were increased in the
straight-grade flour at each increment of added moisture, accompanied by large
increases in extract viscosity. These findings regarding β-glucan and TDF support
the data of Newman et al. (1994). Ames and her group also evaluated the effect of
micronizing on the extractability of β-glucans from milling fractions for possible
development of beverages such as hot barley tea. Significant improvements were
found in the extractability of β-glucans from milling fractions produced from
micronized barley. The extractability of β-glucan was increased in a fine fraction
from 33.6 to 41.6%, and in a coarse fraction from 2.6 to 4.2%, as well as in
whole-meal barley from 15.7 to 21.7%.
Infrared processing or micronizing appears to be a promising processing technique
for improving yield, functionality, and nutritional quality of barley food
products.
SEPARATION TECHNIQUES
Air Classification
Air classification is a separation technique that uses air to effect dry separation
of mixtures having certain characteristics into particle size groups ranging from
2 μm to a maximum of 100 μm, referred to as cut points or cut size. Thecutsize
is defined as the particle size that has a 50–50 chance of ending up in the fine
fraction or in the coarse fraction. In the modern food industry, air classification
is generally utilized to separate particulates in the range 2 to 60 μm. The size,
shape, and density of the particles in the mixture and the physicochemical nature
of the product are the characteristics considered to be important for successful
air classification. The procedure is an operation that applies the technology of
moving air in a confined space to separate nonhomogeneous particles into groups
or classes of fairly uniform size based on density or mass of the particles. In general,
air classifiers will segregate a heterogeneous mixture into two groups, one
primarily below the targeted cut size (fine fraction) and the remainder above this
size (coarse fraction). Such fractions may be reclassified separately to produce
additional fractions. Air classifiers complement screens in applications requiring
cut sizes below commercial screen sizes and supplement sieves and screens for
coarser cuts (Fedec 2003). The general principles of air-classifying devices are as
follows: The material to be classified is suspended in an airstream, the air–solids
stream is introduced into the classification zone, and the coarse fraction is seperated
from the fine fraction and airstream by opposing the drag force created by