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

WHOLE-GRAIN PROCESSING 107
TABLE 5.3 β-Glucan Content of Whole Kernel, Flour, and Bran Produced by
Roller Milling Three Diverse Barley Types (g/100 g), Dry Matter Basis
Barley Type Whole Kernel Flour a Bran b
Hulled (n = 4)
Mean 4.4 4.0 5.1
Range 4.2–4.5 3.9–4.0 4.9–5.4
Hulless (n = 6)
Mean 5.1 4.3 7.1
Range 4.5–5.6 3.8–5.0 6.3–8.1
Hulless waxy (n = 5)
Mean 8.4 6.9 12.3
Range 7.6–11.3 6.3–9.0 10.2–15.4
Source: Bhatty (1992).
a 70% yield.
b 30% yield.
milling procedures. However, when waxy and high-amylose cultivars were milled
using the same flow, the flour yields were less than satisfactory. Modifications of
the flow were made that improved the flour yields of these barleys but still not
achieving the original 74% yield of the normal-starch barley. Lower flour yields
of the waxy and high-amylose cultivars, which had higher levels of β-glucans,
confirmed the findings of Bhatty (1999b) and Sundberg and Åman (1994).
Standard roller milling equipment designed to produce wheat flour may have
to be modified along with procedural modifications to maximize the milling
performance of barley with different types of starch components. Izydorczyk
et al. (2003) postulated that the plasticity of the thick endosperm cell walls of
the high-β-glucan barleys increases the difficulty of obtaining a clean separation
of starch granules and other endosperm cell wall components using the standard
wheat milling techniques of successive break and reduction passages. These
authors reported two milling techniques that were deemed successful. The first
was basically a modified flow normally used in wheat milling as noted above
but considered tedious and time consuming (Figure 5.1). Subsequently, these
researchers developed a short milling flow that was acceptable for evaluating the
milling qualities of the diverse barleys (Figure 5.2). The short flow produced
straight-grade flour yields that were about 2 to 3% lower than the long-flow
procedure, which was in part compensated by a about 3 to 6% higher yield of
a fiber-rich fraction (shorts). However, the β-glucan content of the shorts in the
short-flow operation was less than that obtained in the long-flow procedure.
Pearling rates of 10, 20, 30, and 40% were employed to evaluate the roller
milling of pearled barley using the short-milling flow described above (Izydorczyk
et al. 2003). Yields of flour and shorts were relatively constant when
expressed as a percentage of pearled barley. When expressed on a whole barley
basis, yield of flour and shorts declined as pearling level increased. Flour