134
Chapter 6 · Sweet Chemistry - Mono- and Disaccharides
6
food industry. It is also used for winter-feeding
in bee-keeping, for sweetening tobacco and as
sugar syrup for cocktails.
Like monosaccharides, sucrose can also
be converted into its esters. The three primary
hydroxyl groups of sucrose are particularly reactive, but the five secondary OH groups can also
be esterified. Short-chain carboxylic acids such
as acetic acid or isobutyric acid can be used
as acids. In most cases, however, long-chain
fatty acids are used for esterification to produce
sucrose esters that can be used as surfactants.
This inevitably results in a complex mixture of
multiple esterified molecules (. Fig. 6.22). These
mixtures are relatively hydrophobic and have
only a small application spectrum, e.g. as emulsifiers in cosmetics.
If the eight OH groups are almost completely esterified, a mixture of sucrose octa- and
hepta-fatty acid esters is obtained, which is sold
under the brand name Olestra. It was developed
in 1968 by Procter & Gamble as a fat substitute.
The body’s own lipases cannot degrade this molecule, so it leaves the body undigested. As a food,
however, Olestra has side effects, so it has not
been authorized in Europe.
Another important group of sucrose derivatives are sucrose ether, which can be produced
in various ways. Depending on the degree of substitution and alkyl chain length, these ether can
again be used as non-ionic surfactants that are
non-toxic and readily biodegradable. Compared
to esters, they are much more stable in alkaline
solutions.
5 One possible method of ether synthesis is the
conversion of sucrose with long-chain epoxy
compounds such as 1,2-epoxydodecane
or 1,2-epoxydodecan-3-ol in water or
polar solvents. A mixture of mono- and
diethers is usually formed via splitting of the
three-membered epoxy ring.
5 Alternatively, sucrose can also be converted
in a Williamson synthesis with bromoalkanes, e.g. with bromododecane. Again, a
mixture of mono- and diether is obtained;
NaBr is formed as an unwanted coproduct.
5 An interesting variant is the telomerization of
sucrose with two molecules of 1,3-butadiene.
This reaction is catalyzed by homogeneous palladium complex catalysts and yields
ethers with octadienyl chains (. Fig. 6.23),
which can be hydrogenated to octyl chains.
The viscous, black-brown molasses, which
still contains approx. 50% sugar, remains. The
rest is water (20%), amino acids (6–8%), N-free
organic acids (2–4%), betaines (4–6%) and inorganic components (9–11%). The molasses can
be added to the dry pellets, which are used as
animal feed or as winter-feed for wild animals.
Alternatively, they can also be fermented to alcohol. Jamaica rum is thus produced from cane
sugar molasses.
It should be emphasized that a beet-based
sugar factory only works for about three months
a year. Only during this period, from approx. September to November, the raw material sugar beet
is sufficiently available. Today, modern large-scale
factories process up to 13,000 tons of sugar beets
per day. The quality and quantity of sugar has so
far been regulated by the “European Sugar Market
Regulation”, which has protected the production of
domestic sugar. However, this regulation expired
at the end of 2017. This liberalization of the market has led to a sharp drop in the sugar price in
Europe. In addition, a new competitor recently
appeared on the European sugar market: The EU
and Mercosur, the South American Confederation
of Brazil, Argentina, Paraguay and Uruguay, plan
a common free trade area. In the future, increased
imports of sugar from these South American
countries to Europe could be expected.
6.3.2 Sucrose Processing
In Germany, approximately 3.5 Mio. tons of sucrose
were produced in 2010/2011. 16% of these were
sold as sugar in retail stores; 56% went to the sugar
processing industry and the craft trades. 28% of
the sugar, i.e. approx. 900,000 tons, was processed
in the chemical and other industries (“industrial
sugar”). The sugar is converted into valuable compounds in numerous chemical reactions.
Hydrolysis to invert sugar has already been
mentioned. In this reaction, the disaccharide
sucrose is split into the two monosaccharides
glucose and fructose. This reaction takes place
either with diluted mineral acids or with specific enzymes, so-called invertases. Recently,
immobilized enzymes, cation exchange resins
(in the H + form), zeolites and silica-supported
heteropolyacids have also been used for this
purpose. Invert sugar is processed into liquid
sugar and artificial honey, which are used in the
Chapter 6 · Sweet Chemistry - Mono- and Disaccharides
6
food industry. It is also used for winter-feeding
in bee-keeping, for sweetening tobacco and as
sugar syrup for cocktails.
Like monosaccharides, sucrose can also
be converted into its esters. The three primary
hydroxyl groups of sucrose are particularly reactive, but the five secondary OH groups can also
be esterified. Short-chain carboxylic acids such
as acetic acid or isobutyric acid can be used
as acids. In most cases, however, long-chain
fatty acids are used for esterification to produce
sucrose esters that can be used as surfactants.
This inevitably results in a complex mixture of
multiple esterified molecules (. Fig. 6.22). These
mixtures are relatively hydrophobic and have
only a small application spectrum, e.g. as emulsifiers in cosmetics.
If the eight OH groups are almost completely esterified, a mixture of sucrose octa- and
hepta-fatty acid esters is obtained, which is sold
under the brand name Olestra. It was developed
in 1968 by Procter & Gamble as a fat substitute.
The body’s own lipases cannot degrade this molecule, so it leaves the body undigested. As a food,
however, Olestra has side effects, so it has not
been authorized in Europe.
Another important group of sucrose derivatives are sucrose ether, which can be produced
in various ways. Depending on the degree of substitution and alkyl chain length, these ether can
again be used as non-ionic surfactants that are
non-toxic and readily biodegradable. Compared
to esters, they are much more stable in alkaline
solutions.
5 One possible method of ether synthesis is the
conversion of sucrose with long-chain epoxy
compounds such as 1,2-epoxydodecane
or 1,2-epoxydodecan-3-ol in water or
polar solvents. A mixture of mono- and
diethers is usually formed via splitting of the
three-membered epoxy ring.
5 Alternatively, sucrose can also be converted
in a Williamson synthesis with bromoalkanes, e.g. with bromododecane. Again, a
mixture of mono- and diether is obtained;
NaBr is formed as an unwanted coproduct.
5 An interesting variant is the telomerization of
sucrose with two molecules of 1,3-butadiene.
This reaction is catalyzed by homogeneous palladium complex catalysts and yields
ethers with octadienyl chains (. Fig. 6.23),
which can be hydrogenated to octyl chains.
The viscous, black-brown molasses, which
still contains approx. 50% sugar, remains. The
rest is water (20%), amino acids (6–8%), N-free
organic acids (2–4%), betaines (4–6%) and inorganic components (9–11%). The molasses can
be added to the dry pellets, which are used as
animal feed or as winter-feed for wild animals.
Alternatively, they can also be fermented to alcohol. Jamaica rum is thus produced from cane
sugar molasses.
It should be emphasized that a beet-based
sugar factory only works for about three months
a year. Only during this period, from approx. September to November, the raw material sugar beet
is sufficiently available. Today, modern large-scale
factories process up to 13,000 tons of sugar beets
per day. The quality and quantity of sugar has so
far been regulated by the “European Sugar Market
Regulation”, which has protected the production of
domestic sugar. However, this regulation expired
at the end of 2017. This liberalization of the market has led to a sharp drop in the sugar price in
Europe. In addition, a new competitor recently
appeared on the European sugar market: The EU
and Mercosur, the South American Confederation
of Brazil, Argentina, Paraguay and Uruguay, plan
a common free trade area. In the future, increased
imports of sugar from these South American
countries to Europe could be expected.
6.3.2 Sucrose Processing
In Germany, approximately 3.5 Mio. tons of sucrose
were produced in 2010/2011. 16% of these were
sold as sugar in retail stores; 56% went to the sugar
processing industry and the craft trades. 28% of
the sugar, i.e. approx. 900,000 tons, was processed
in the chemical and other industries (“industrial
sugar”). The sugar is converted into valuable compounds in numerous chemical reactions.
Hydrolysis to invert sugar has already been
mentioned. In this reaction, the disaccharide
sucrose is split into the two monosaccharides
glucose and fructose. This reaction takes place
either with diluted mineral acids or with specific enzymes, so-called invertases. Recently,
immobilized enzymes, cation exchange resins
(in the H + form), zeolites and silica-supported
heteropolyacids have also been used for this
purpose. Invert sugar is processed into liquid
sugar and artificial honey, which are used in the