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Chapter 8 · Products with a Little Twist - Starch
8
Pregelatinized starches are starches that
form dispersions in cold water without clumping when used correctly. To achieve this, a
starch-water mixture is treated on a hot roller,
scraped off, dried and ground to powder. This
serves primarily to destroy the starch grains. In
order to further increase the shear forces, the
water-starch mixture can also be fed into the
gap of two counter-rotating rollers heated with
steam. These starches are mainly used in the food
sector, in applications where the product is not
boiled, e.g. in cold stirred puddings. Another
application is in the detergent sector.
A special form of starch preparation goes
back to K. Zulkowsky, who found at the end of
the nineteenth century that starch (especially
potato starch) dissolves particularly well in hot
glycerol. If approx. 0.6 wt% potato starch is dissolved in glycerol at 190 °C, it changes into a soluble form. The starch can be isolated in this form
by pouring the cooled solution into ethanol to
form a powdery precipitate. This soluble starch
is commercially available and is used, for example, in analytical applications. It is much more
soluble in water than common soluble starch.
8.4.1 Partially Hydrolyzed Starches
Thinned starch is a starch degradation product produced from a suspension of native starch
by acid catalyzed cleavage of a few glycosidic
bonds. It can be used as a thickening agent and,
as a food ingredient, does not require labeling
because it is only slightly different from native
starch. The DE at these very low conversions is
almost equal to the DE value for native starch.
Dextrins are also starch products which are
formed by the partial hydrolysis of the glycosidic
bond. However, the degree of depolymerization is
higher compared to thinned. Another difference
is that dextrins are not produced from a solution
or suspension, but from starch powder. They can
also be produced without the addition of acids;
under elevated temperature of about 150 °C,
“roasted dextrins” are formed. When working
under acidic conditions, HCl is frequently used,
either as a concentrated solution or as a gas.
White and yellow dextrins exist differing, among
other things, in the degree of depolymerization
and in the manufacturing temperature. Lighter
dextrins are used in the food and textile indusIn 2016, approximately 9.3 Mio. tons of
starches and starch derivatives were consumed in
the EU. With approx. 55%, saccharification products account for the largest share, along with 26%
native and 19% modified starch (. Fig. 8.5). Significantly more than half (approx. 61%) is used in
food. Typical applications of native and modified
starches are bakery products, confectionery and
dairy products, the use to increase the viscosity of
liquid foods and, in a saccharified form, as sweeteners in beverages. The high-fructose corn syrup
(HFCS), which is produced from starch and has
largely replaced table sugar for sweetening soft
drinks in the USA, for example, is particularly
worth mentioning here (7 Sect. 8.4.2).
The next most important application of starch
is material or industrial use. Approximately
39% of starch products manufactured in the EU
are used in this so-called non-food sector. The
application in the paper industry plays an important role, e.g. for impregnating paper against ink
bleeding or for gluing corrugated board. Only
about 6% of the starch is used in the chemical
industry or as a nutrient medium for fermentations. Another important example is thermoplastic starch. This is obtained by treating native
starch in extruders under the influence of temperature, shear forces and pressure with the addition of plasticizers such as glycerol. This destroys
the starch grains and reduces crystallinity. At the
same time, brittleness is reduced, which simplifies processing. Thermoplastic starch is mixed
with other components to produce so-called
starch blends used for products with comparatively short life times, such as packaging chips,
compostable disposable cutlery or shopping bags.
Typical blending components are biodegradable
petrochemical polymers, bioplastics or inorganic
materials. Starch blends currently account for
around 18% of bioplastics (7 Chap. 19).
Starch is also used in the cosmetics industry.
In the USA and EU, the production of bioethanol by fermentation is mainly based on the use of
starch, while in Brazil, it is based on sugar from
sugar cane (7 Chap. 20).
8.4 Starch Products
In this section, important products made from
starch are discussed in more detail. An overview
is given at . Fig. 8.6.
Chapter 8 · Products with a Little Twist - Starch
8
Pregelatinized starches are starches that
form dispersions in cold water without clumping when used correctly. To achieve this, a
starch-water mixture is treated on a hot roller,
scraped off, dried and ground to powder. This
serves primarily to destroy the starch grains. In
order to further increase the shear forces, the
water-starch mixture can also be fed into the
gap of two counter-rotating rollers heated with
steam. These starches are mainly used in the food
sector, in applications where the product is not
boiled, e.g. in cold stirred puddings. Another
application is in the detergent sector.
A special form of starch preparation goes
back to K. Zulkowsky, who found at the end of
the nineteenth century that starch (especially
potato starch) dissolves particularly well in hot
glycerol. If approx. 0.6 wt% potato starch is dissolved in glycerol at 190 °C, it changes into a soluble form. The starch can be isolated in this form
by pouring the cooled solution into ethanol to
form a powdery precipitate. This soluble starch
is commercially available and is used, for example, in analytical applications. It is much more
soluble in water than common soluble starch.
8.4.1 Partially Hydrolyzed Starches
Thinned starch is a starch degradation product produced from a suspension of native starch
by acid catalyzed cleavage of a few glycosidic
bonds. It can be used as a thickening agent and,
as a food ingredient, does not require labeling
because it is only slightly different from native
starch. The DE at these very low conversions is
almost equal to the DE value for native starch.
Dextrins are also starch products which are
formed by the partial hydrolysis of the glycosidic
bond. However, the degree of depolymerization is
higher compared to thinned. Another difference
is that dextrins are not produced from a solution
or suspension, but from starch powder. They can
also be produced without the addition of acids;
under elevated temperature of about 150 °C,
“roasted dextrins” are formed. When working
under acidic conditions, HCl is frequently used,
either as a concentrated solution or as a gas.
White and yellow dextrins exist differing, among
other things, in the degree of depolymerization
and in the manufacturing temperature. Lighter
dextrins are used in the food and textile indusIn 2016, approximately 9.3 Mio. tons of
starches and starch derivatives were consumed in
the EU. With approx. 55%, saccharification products account for the largest share, along with 26%
native and 19% modified starch (. Fig. 8.5). Significantly more than half (approx. 61%) is used in
food. Typical applications of native and modified
starches are bakery products, confectionery and
dairy products, the use to increase the viscosity of
liquid foods and, in a saccharified form, as sweeteners in beverages. The high-fructose corn syrup
(HFCS), which is produced from starch and has
largely replaced table sugar for sweetening soft
drinks in the USA, for example, is particularly
worth mentioning here (7 Sect. 8.4.2).
The next most important application of starch
is material or industrial use. Approximately
39% of starch products manufactured in the EU
are used in this so-called non-food sector. The
application in the paper industry plays an important role, e.g. for impregnating paper against ink
bleeding or for gluing corrugated board. Only
about 6% of the starch is used in the chemical
industry or as a nutrient medium for fermentations. Another important example is thermoplastic starch. This is obtained by treating native
starch in extruders under the influence of temperature, shear forces and pressure with the addition of plasticizers such as glycerol. This destroys
the starch grains and reduces crystallinity. At the
same time, brittleness is reduced, which simplifies processing. Thermoplastic starch is mixed
with other components to produce so-called
starch blends used for products with comparatively short life times, such as packaging chips,
compostable disposable cutlery or shopping bags.
Typical blending components are biodegradable
petrochemical polymers, bioplastics or inorganic
materials. Starch blends currently account for
around 18% of bioplastics (7 Chap. 19).
Starch is also used in the cosmetics industry.
In the USA and EU, the production of bioethanol by fermentation is mainly based on the use of
starch, while in Brazil, it is based on sugar from
sugar cane (7 Chap. 20).
8.4 Starch Products
In this section, important products made from
starch are discussed in more detail. An overview
is given at . Fig. 8.6.