170
Chapter 8 · Products with a Little Twist - Starch
8
tion, these syrups are subject to production regulations in the EU and may only be produced to a
limited extent.
Controversially discussed in connection with
the use of GFS as a sweetener is above all the
health aspect of the increased intake of fructose:
In sucrose, glucose and fructose occur in equal
proportions, but HFCS-55 with 55% fructose and
only about 41% glucose has a significantly higher
fructose content. Since fructose is metabolized
independently of insulin, but insulin is important
for a feeling of satiety, increased fructose intake
promotes overweight and high blood pressure.
d-Sorbitol is the reduced polyol derivative of
the sugars d-glucose, d-fructose and d-sorbose.
Sorbitol is therefore one of the sugar alcohols. It can be produced from glucose syrups.
Sugar alcohols have already been discussed in
7 Chap. 6.
8.4.3 Chemical Derivatization
of Starch
Chemically, starch can also be seen as a macromolecular polyol. Therefore, starch is also accessible for the “classical” chemistry of alcohols.
By substituting the alcohol group, e.g. ester or
ether groups can be introduced. In principle,
however, the polymer structure of the starch is
retained. “Size reduction” of the starch is therefore not targeted, as was the case with hydrolysis. Of course, hydrolyzed starch can also be
derivatized.
Potentially, the hydroxyl functions at the glucose positions C2, 3 and 6 are available in the
starch for the substitution reactions. The products in which relatively few hydroxyl groups
have been substituted are important from an
industrial and food technology point of view.
Larger alterations in starch properties can be
achieved, for example, with a degree of substitution of 0.01–0.1 only. However, products with
a much lower degree of substitution are also
important. The DS has already been explained in
7 Chap. 7 “Cellulose”. Derivatization can also be
performed with bi- or polyfunctional reagents,
which lead to inter- and intramolecular bridging within the starch. These products are referred
to as “cross-linked starches” (see Cellulose ester,
7 Sect. 7.3).
as sweeteners for soft drinks or confectionery. Smaller quantities are also produced for
industrial applications as antifreeze or de-icing agent. Most glucose syrups are produced
in two stages: In a first step, the starch suspension is liquefied at elevated temperatures
by temperature-stable-amylases, before being
reacted in a second step with other enzymes
to the desired degree of depolymerization. The
syrup is then clarified, decolorized and concentrated. DE values of 20–95 are achievable, with
mixtures with a lower DE value containing many
malto-oligosaccharides and mixtures with a high
DE value mainly containing glucose.
Pure d-glucose can be crystallized from glucose syrups by adding pure d-glucose as seed crystals to syrups with a high DE value, typically >90.
Since d-fructose has a sweetening power
which is about 20% higher than that of
d-glucose, it is economical to enrich glucose
syrups enzymatically with fructose to form glucose-fructose syrup, achieving the same sweetening power with less input material. For this
purpose, a glucose solution is treated with the
enzyme glucose isomeraze immobilized in a
fixed bed. An equilibrium distribution of about
58% d-glucose and 42% d-fructose is reached.
Modern separation processes now make it possible to increase the fructose content to 90%.
Glucose-fructose syrups (GFS) produced in
this way are used as sweeteners in food (mainly
in desserts) and beverages, especially soft drinks.
For the latter, a mixture of 42% and 90% syrup is
usually used (high-fructose corn syrup, HFCS),
which contains 55% fructose. This sweetener,
which is mainly used in the beverage industry,
has a sweetening power comparable to sucrose,
which is why this special mixture is particularly
interesting. However, glucose-fructose syrups
are significantly cheaper than sucrose (sucrose,
7 Sect. 6.2), as they can be produced from relatively cheap starch. These syrups originate in the
USA precisely for this reason: Corn cultivation
(for starch production) has long been subsidized
in the USA and genetically modified corn is cultivated on huge areas. The import of sugar, on
the other hand, has to be taxed, so that there is a
particularly large price benefit here. In Germany,
on the other hand, sugar beet cultivation is subsidized, so that the GFS’s success in this country
in the beverage industry is slowed down. In addi-
Chapter 8 · Products with a Little Twist - Starch
8
tion, these syrups are subject to production regulations in the EU and may only be produced to a
limited extent.
Controversially discussed in connection with
the use of GFS as a sweetener is above all the
health aspect of the increased intake of fructose:
In sucrose, glucose and fructose occur in equal
proportions, but HFCS-55 with 55% fructose and
only about 41% glucose has a significantly higher
fructose content. Since fructose is metabolized
independently of insulin, but insulin is important
for a feeling of satiety, increased fructose intake
promotes overweight and high blood pressure.
d-Sorbitol is the reduced polyol derivative of
the sugars d-glucose, d-fructose and d-sorbose.
Sorbitol is therefore one of the sugar alcohols. It can be produced from glucose syrups.
Sugar alcohols have already been discussed in
7 Chap. 6.
8.4.3 Chemical Derivatization
of Starch
Chemically, starch can also be seen as a macromolecular polyol. Therefore, starch is also accessible for the “classical” chemistry of alcohols.
By substituting the alcohol group, e.g. ester or
ether groups can be introduced. In principle,
however, the polymer structure of the starch is
retained. “Size reduction” of the starch is therefore not targeted, as was the case with hydrolysis. Of course, hydrolyzed starch can also be
derivatized.
Potentially, the hydroxyl functions at the glucose positions C2, 3 and 6 are available in the
starch for the substitution reactions. The products in which relatively few hydroxyl groups
have been substituted are important from an
industrial and food technology point of view.
Larger alterations in starch properties can be
achieved, for example, with a degree of substitution of 0.01–0.1 only. However, products with
a much lower degree of substitution are also
important. The DS has already been explained in
7 Chap. 7 “Cellulose”. Derivatization can also be
performed with bi- or polyfunctional reagents,
which lead to inter- and intramolecular bridging within the starch. These products are referred
to as “cross-linked starches” (see Cellulose ester,
7 Sect. 7.3).
as sweeteners for soft drinks or confectionery. Smaller quantities are also produced for
industrial applications as antifreeze or de-icing agent. Most glucose syrups are produced
in two stages: In a first step, the starch suspension is liquefied at elevated temperatures
by temperature-stable-amylases, before being
reacted in a second step with other enzymes
to the desired degree of depolymerization. The
syrup is then clarified, decolorized and concentrated. DE values of 20–95 are achievable, with
mixtures with a lower DE value containing many
malto-oligosaccharides and mixtures with a high
DE value mainly containing glucose.
Pure d-glucose can be crystallized from glucose syrups by adding pure d-glucose as seed crystals to syrups with a high DE value, typically >90.
Since d-fructose has a sweetening power
which is about 20% higher than that of
d-glucose, it is economical to enrich glucose
syrups enzymatically with fructose to form glucose-fructose syrup, achieving the same sweetening power with less input material. For this
purpose, a glucose solution is treated with the
enzyme glucose isomeraze immobilized in a
fixed bed. An equilibrium distribution of about
58% d-glucose and 42% d-fructose is reached.
Modern separation processes now make it possible to increase the fructose content to 90%.
Glucose-fructose syrups (GFS) produced in
this way are used as sweeteners in food (mainly
in desserts) and beverages, especially soft drinks.
For the latter, a mixture of 42% and 90% syrup is
usually used (high-fructose corn syrup, HFCS),
which contains 55% fructose. This sweetener,
which is mainly used in the beverage industry,
has a sweetening power comparable to sucrose,
which is why this special mixture is particularly
interesting. However, glucose-fructose syrups
are significantly cheaper than sucrose (sucrose,
7 Sect. 6.2), as they can be produced from relatively cheap starch. These syrups originate in the
USA precisely for this reason: Corn cultivation
(for starch production) has long been subsidized
in the USA and genetically modified corn is cultivated on huge areas. The import of sugar, on
the other hand, has to be taxed, so that there is a
particularly large price benefit here. In Germany,
on the other hand, sugar beet cultivation is subsidized, so that the GFS’s success in this country
in the beverage industry is slowed down. In addi-