Chemical and Functional Properties of Food Saccharides

a large concentration phospholipid (0.06%), whereas normal maize starch consists
of mainly free fatty acids, some glycerides, and little phospholipids (~0.01%). 10,12,13
The difference in pasting temperature between normal wheat and waxy wheat
starches, measured by a Rapid Visco Amylograph at a heating rate of 6°C/min, is
28.1°C, whereas the difference between normal maize and waxy maize starches is
only 11.7°C. The peak viscosity of waxy wheat starch is 134 RVU (rapid viscosity
units) greater than that of normal wheat starch, compared with the 41 RVU difference
between waxy and normal maize starch (Figure 7.4). 14 The extremely high pasting
temperature and low peak viscosity of normal wheat starch are attributed to its high
phospholipid content. 14 Phospholipids form the helical complex with amylose and
with the long branch chains of amylopectin. The helical complex entangles with
amylopectin molecules and prohibits swelling of starch granules. However, waxy
starches consist of little or no amylose and have little lipids, thus display lower
pasting temperatures and unrestricted swelling to a greater peak viscosity. After
ultrahigh-pressure treatments, starch pasting properties change, depending on lipid
content, molecular structure, and crystalline structures. 81,82
Waxy starches consist of 92 to 100% amylopectin, and amylopectin molecules
in starch granules are primarily responsible for the swelling power of starch. 83 Higher
amylopectin content of waxy starches also contributes to greater viscosity of waxy
starch pastes. High-amylose starches, such as high-amylose maize 40 and high-amylose
barley, 84 display little viscosity, which can be attributed to their lower amylopectin
contents and higher amylose and lipids contents.
RVU
250
200
150
100
50
© 2004 by CRC Press LLC
0
0
0 5 10 15 20 25 30
Time (min)
Waxy wheat Kanto107 Centura
Commercial wheat Waxy maize Normal maize
FIGURE 7.4 Pasting profiles of waxy wheat starch, semiwaxy wheat starch (Kanto 107),
and normal wheat starches (Centura and Commercial wheat) compared with those of normal
and waxy maize starches. Arrows stand for differences between normal and waxy starch
counterparts.
100
80
60
40
20
Temperature (°C)