162
Chapter 8 · Products with a Little Twist - Starch
8
result, it has an average molecular weight
in the range of 100,000 to 1,000,000 Dalton.
Amylose does not have any branches and
forms intramolecularly a helical structure,
a so-called helix (. Fig. 8.2). One turn of
this helix is formed from about six glucose
monomers. Other molecules, e.g. iodine
(more precisely I
−
3 ) can migrate in the
hollow space of the helix. This effect is
used in the iodine test, since the inclusion
compound formed has a deep blue to dark
violet color.
5 Like amylose, amylopectin is composed
exclusively of glucose monomers. On
average, about 6000 of these units are
linked in a single molecule, and after about
25 α-1,4-glycosidic bonds, there is one
α-1,6-glycosidic branch. This branching can
also take place between two adjacent polymer
molecules, resulting in a further branched
polymer network. As a result, amylopectin
does not form ordered super-structures and
has an average molecular weight of 10–200
million Dalton, which is up to two orders of
magnitude higher than amylose.
Chapter Timetable
5 The chemical structure of starch as well as
its composition is discussed. You will get
to know the most important sources of
starch and its industrial production.
5 We discuss the material use of starch
and its chemical transformation into
interesting derivatives.
8.1 Structure and Occurrence
Starch (lat. amylum) is a polysaccharide and,
just like cellulose, consists of the building block
d-glucose. In contrast to cellulose, the glucose
units are linked via an α-1,4-glycosidic bond
(7 Sect. 6.1). Starch is stored in plant cells as an
energy reserve. Starch is a mixture of two substances, namely amylose and amlyopectin, both
of which are made up of glucose but have slightly
different structures and properties (. Fig. 8.1):
5 Amylose is composed of about 1000–4500
glucose units, which are linked via a glycosidic bond between carbons 1 and 4. As a
. Fig. 8.1 Structural
formulae of amylose (top)
and amylopectin (bottom)
O
H
HO
OH O
CH 2 OH
O
HO
OH O
O
H
H
H
H
H
H
H
H
H
4
1
4
1
CH 2 OH
O
HO
OH
O
H
H
H
H
H
1
4
CH 2 OH
O
H
HO
OH
O
CH 2 OH
O
HO
OH O
O
H
H
H
H
H
H
H
H
H
4
1
4
1
CH 2 OH
O
H
HO
OH
O
CH 2 OH
O
HO
OH O
O
H
H
H
H
H
H
H
H
H
4
1
4
1
6
α
α
α
α
α
α
α
Chapter 8 · Products with a Little Twist - Starch
8
result, it has an average molecular weight
in the range of 100,000 to 1,000,000 Dalton.
Amylose does not have any branches and
forms intramolecularly a helical structure,
a so-called helix (. Fig. 8.2). One turn of
this helix is formed from about six glucose
monomers. Other molecules, e.g. iodine
(more precisely I
−
3 ) can migrate in the
hollow space of the helix. This effect is
used in the iodine test, since the inclusion
compound formed has a deep blue to dark
violet color.
5 Like amylose, amylopectin is composed
exclusively of glucose monomers. On
average, about 6000 of these units are
linked in a single molecule, and after about
25 α-1,4-glycosidic bonds, there is one
α-1,6-glycosidic branch. This branching can
also take place between two adjacent polymer
molecules, resulting in a further branched
polymer network. As a result, amylopectin
does not form ordered super-structures and
has an average molecular weight of 10–200
million Dalton, which is up to two orders of
magnitude higher than amylose.
Chapter Timetable
5 The chemical structure of starch as well as
its composition is discussed. You will get
to know the most important sources of
starch and its industrial production.
5 We discuss the material use of starch
and its chemical transformation into
interesting derivatives.
8.1 Structure and Occurrence
Starch (lat. amylum) is a polysaccharide and,
just like cellulose, consists of the building block
d-glucose. In contrast to cellulose, the glucose
units are linked via an α-1,4-glycosidic bond
(7 Sect. 6.1). Starch is stored in plant cells as an
energy reserve. Starch is a mixture of two substances, namely amylose and amlyopectin, both
of which are made up of glucose but have slightly
different structures and properties (. Fig. 8.1):
5 Amylose is composed of about 1000–4500
glucose units, which are linked via a glycosidic bond between carbons 1 and 4. As a
. Fig. 8.1 Structural
formulae of amylose (top)
and amylopectin (bottom)
O
H
HO
OH O
CH 2 OH
O
HO
OH O
O
H
H
H
H
H
H
H
H
H
4
1
4
1
CH 2 OH
O
HO
OH
O
H
H
H
H
H
1
4
CH 2 OH
O
H
HO
OH
O
CH 2 OH
O
HO
OH O
O
H
H
H
H
H
H
H
H
H
4
1
4
1
CH 2 OH
O
H
HO
OH
O
CH 2 OH
O
HO
OH O
O
H
H
H
H
H
H
H
H
H
4
1
4
1
6
α
α
α
α
α
α
α