Answers to the Quickies
363
Answers to 7 Chap. 8
1. Starch consists of amylose and amylopectin. Both substances are polysaccharides
built up from d-glucose monomers. In
amylose, these monomers are exclusively
linked to each other via an α-1,4-glycosidic
bond. Amylose therefore forms a helical
structure. In amylopectin, an intermolecular branching occurs at about every 25th
glucose monomer between neighboring
polymer chains via the carbons C1 and C6.
Amylopectin therefore forms a tree-like
network.
2. Important raw materials for starch production are corn, wheat, potatoes, manioc and
rice. While in Germany starch is mainly
obtained from potatoes, maize is the most
important starch supplier worldwide.
3. Native starch is starch in its original, natural
form, as it occurs, for example, in potatoes.
It is characterized by the fact that it forms
starch grains. In the case of modified starch,
physical or chemical changes have been
made to native starch in order to achieve the
desired property changes.
4. Partial hydrolysis of starch produces
thin-boiling starch, dextrins and maltodextrins.
5. The glycosidic bond in starch can be split
either by acids, e.g. with HCl, or by special
enzymes, the amylases.
6. The dextrose equivalent (DE) indicates the
proportion of reducing sugars in the total
mass of a formulation. By definition, starch
has a DE of 0, with increasing degradation
of the starch the DE increases. Glucose has
a DE of 100, which is reached when starch is
completely hydrolyzed.
7. Starch is first liquefied at elevated temperatures with temperature-stable α-amylases
and then broken down to glucose.
The glucose solution is converted into a
mixture of 58% glucose and 42% fructose
using immobilized enzymes. Using special
separation processes, the fructose content
can be further increased to 90%. A mixture
of 42 and 90% syrup results in HFCS with a
fructose content of 55%, which has the same
sweetening power as household sugar.
8. Starch phosphates are esters of starch with
the inorganic phosphoric acid and starch
acetates are esters of starch with the organic
acetic acid.
9. The etherification of starch can be carried
out with halogen compounds according
to Williamson ether synthesis, with
epoxides or with lactones to the desired
starch ethers.
10. If starch is oxidized with periodic acid or
periodates, the vicinal alcohol groups on
the carbon atoms C2 and C3 of the starch
are cleaved; first the “dialdehyde starch” is
formed, which can then react to the “dicarboxylic starch”.
Answers to 7 Chap. 9
1. Chitin occurs in nature mainly in the exoskeletons of invertebrates, i.e. in insects and
crustaceans. It is also found in the cell walls
of some lower plants and in fungi. Chitosan
occurs in nature, for example, in the cell
walls of special fungi.
2. Chitin is a polysaccharide, composed of
N-acetylglucosamine monomers, which are
linked via a β-1,4-glycosidic bond. The difference to chitosan is that the amino groups
of chitosan are deacetylated. One refers to
chitosan, if the proportion of free amino
groups in the polysaccharide is >50%.
3. Chitin and cellulose both are polysaccharides, which are composed exclusively of a
single sugar unit. In both, the monomers are
linked via a β-1,4-glycosidic bond. In chitin,
the hydroxyl function at the C2 atom of the
sugar monomer is replaced by an acetamido
group. Both polysaccharides form strongly
ordered, fibrillar superstructures and are
therefore insoluble in water.
4. Crustacean waste from shrimp fishing is
used as raw material for the production of
chitin. This material is available in large but
so far little-used quantities.
5. Chitin occurs in the shell of crustaceans
together with proteins (sclerotin) and
minerals (calcium carbonate) in a composite structure. Therefore, the proteins must
be removed by deproteinization (e.g. with
NaOH) and the minerals by demineralization (e.g. with HCl) before the chitin is isolated. After washing, drying and grinding,
chitin is obtained as a colorless powder.
363
Answers to 7 Chap. 8
1. Starch consists of amylose and amylopectin. Both substances are polysaccharides
built up from d-glucose monomers. In
amylose, these monomers are exclusively
linked to each other via an α-1,4-glycosidic
bond. Amylose therefore forms a helical
structure. In amylopectin, an intermolecular branching occurs at about every 25th
glucose monomer between neighboring
polymer chains via the carbons C1 and C6.
Amylopectin therefore forms a tree-like
network.
2. Important raw materials for starch production are corn, wheat, potatoes, manioc and
rice. While in Germany starch is mainly
obtained from potatoes, maize is the most
important starch supplier worldwide.
3. Native starch is starch in its original, natural
form, as it occurs, for example, in potatoes.
It is characterized by the fact that it forms
starch grains. In the case of modified starch,
physical or chemical changes have been
made to native starch in order to achieve the
desired property changes.
4. Partial hydrolysis of starch produces
thin-boiling starch, dextrins and maltodextrins.
5. The glycosidic bond in starch can be split
either by acids, e.g. with HCl, or by special
enzymes, the amylases.
6. The dextrose equivalent (DE) indicates the
proportion of reducing sugars in the total
mass of a formulation. By definition, starch
has a DE of 0, with increasing degradation
of the starch the DE increases. Glucose has
a DE of 100, which is reached when starch is
completely hydrolyzed.
7. Starch is first liquefied at elevated temperatures with temperature-stable α-amylases
and then broken down to glucose.
The glucose solution is converted into a
mixture of 58% glucose and 42% fructose
using immobilized enzymes. Using special
separation processes, the fructose content
can be further increased to 90%. A mixture
of 42 and 90% syrup results in HFCS with a
fructose content of 55%, which has the same
sweetening power as household sugar.
8. Starch phosphates are esters of starch with
the inorganic phosphoric acid and starch
acetates are esters of starch with the organic
acetic acid.
9. The etherification of starch can be carried
out with halogen compounds according
to Williamson ether synthesis, with
epoxides or with lactones to the desired
starch ethers.
10. If starch is oxidized with periodic acid or
periodates, the vicinal alcohol groups on
the carbon atoms C2 and C3 of the starch
are cleaved; first the “dialdehyde starch” is
formed, which can then react to the “dicarboxylic starch”.
Answers to 7 Chap. 9
1. Chitin occurs in nature mainly in the exoskeletons of invertebrates, i.e. in insects and
crustaceans. It is also found in the cell walls
of some lower plants and in fungi. Chitosan
occurs in nature, for example, in the cell
walls of special fungi.
2. Chitin is a polysaccharide, composed of
N-acetylglucosamine monomers, which are
linked via a β-1,4-glycosidic bond. The difference to chitosan is that the amino groups
of chitosan are deacetylated. One refers to
chitosan, if the proportion of free amino
groups in the polysaccharide is >50%.
3. Chitin and cellulose both are polysaccharides, which are composed exclusively of a
single sugar unit. In both, the monomers are
linked via a β-1,4-glycosidic bond. In chitin,
the hydroxyl function at the C2 atom of the
sugar monomer is replaced by an acetamido
group. Both polysaccharides form strongly
ordered, fibrillar superstructures and are
therefore insoluble in water.
4. Crustacean waste from shrimp fishing is
used as raw material for the production of
chitin. This material is available in large but
so far little-used quantities.
5. Chitin occurs in the shell of crustaceans
together with proteins (sclerotin) and
minerals (calcium carbonate) in a composite structure. Therefore, the proteins must
be removed by deproteinization (e.g. with
NaOH) and the minerals by demineralization (e.g. with HCl) before the chitin is isolated. After washing, drying and grinding,
chitin is obtained as a colorless powder.