between starch and other components

between starch and other components (e.g., lipids, proteins) might also be
described as physical modifications. Through genetic modification, the composition, in terms of amylose and amylopectin, might also be changed. The
aim of all these modifications is to improve the functional properties of starch.
Starch is basically composed of a mixture of amylose and amylopectin.
The composition of these starch molecules is fairly simple; they are polymers
built up from only one type of monomer — glucose. It is still possible to have
from this chapter, in the physicochemical and functional properties.
10.2 THE STARCH GRANULE
Various starches differ considerably from each other in properties. It has been
suggested that no two granules, even from the same botanical origin, are
similar; “in fact, it is probably no exaggeration to say that each granule in a
population is unique, differing from its neighbors in terms of both fine structure
and properties” [1]. All granules are thus individuals. Still, it is possible to
identify properties of a typical starch that put starch in a category of its own
among polysaccharides. Starch is found in nature as particles. These particles
cause starch systems to behave like suspensions or dispersions. After heating
and mechanical treatment in food processing, remnants of the starch particle
are left.
The particle, of course, has a surface, and the importance of this surface
with regard to interactions between the starch and other components should
be given some attention. One example of how the starch surface comes into
play is enzymatic digestion. A prerequisite for hydrolysis is that the enzymes
are adsorbed onto the starch granule [2]. The hydrolysis may then proceed
either through surface erosion or through penetration through pinholes and
subsequent hydrolysis from the inside out [3].
The interior of the starch granule is composed of alternating crystalline
and amorphous regions. Starch is frequently described as a semicrystalline or
partly crystalline polymer [4–7]. The melting of crystallites and disruption of
the organized structure are the basis for gelatinization.
10.2.1 THESTARCHPARTICLE
10.2.1.1 Morphological Aspects
The shape of the starch granule depends on the botanical source, and many
different forms are found in nature. Also, the size varies, from the tiny granules
in rice and oat to the large ones in potato and banana starch. Some typical
(wheat, rye, and barley) show a bimodal size distribution. The small granules
© 2006 by Taylor & Francis Group, LLC
great variation in the chemical structures (see Chapter 9) and, as will be clear