Glucose syrup
Encyclopedia
Glucose syrup is a food syrup
, made from the hydrolysis
of starch
. Maize
is commonly used as the source of the starch in the USA, in which case the syrup is called "corn syrup
", but glucose syrup is also made from other starch crops, including potato
es, wheat
, barley
, rice
and cassava
p.21. Glucose syrup containing over 90% glucose
is used in industrial fermentation
p.230, but syrups used in confectionery
manufacture contain varying amounts of glucose
, maltose
and higher oligosaccharide
s, depending on the grade, and can typically contain 10% to 43% glucose.p.132 Glucose syrup is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor. By converting some of the glucose in corn syrup into fructose
(using an enzymatic
process), a sweeter product, high-fructose corn syrup can be produced.
(DE). The further the hydrolysis process proceeds, the more reducing sugars are produced, and the higher the DE. Depending on the process used, glucose syrups with different compositions, and hence different technical properties, can have the same DE.
and other byproducts.p.26 This type of product is now manufactured using a continuous process and is still widely used due to the low cost of acid hydrolysis. The sugar profile of a confectioner's syrup can also be mimicked by enzyme hydrolysis. A typical confectioner's syrup contains 19% glucose, 14% maltose, 11% maltotriose
and 56% higher molecular mass
carbohydrate
s.p.464
, glucose syrups containing over 50% maltose, or even over 70% maltose (extra-high-maltose syrup) can be producedp.465. This is possible because these enzymes remove two glucose units (i.e. one maltose molecule) at a time from the end of the starch molecule. High-maltose glucose syrup has a great advantage in the production of hard candy: at a given moisture level and temperature, a maltose solution has a lower viscosity than a glucose solution, but will still set to a hard product. Maltose is also less humectant than glucose, so that candy produced with high-maltose syrup will not become sticky as easily as candy produced with a standard glucose syrupp.81.
.p.22) Protein produces off-flavours and colours due to the Maillard reaction
, and fibre is insoluble and has to be removed to allow the starch to become hydrated. The plant material also needs to be ground as part of this process to expose the starch to the water.
is added to prevent spoilage.
takes place: the intermolecular bonds of the starch
molecules are broken down, allowing the hydrogen bond
ing sites to engage more water. This irreversibly dissolves the starch granule
, so that the chains begin to separate into an amorphous form. This prepares the starch for hydrolysis.
, enzyme hydrolysis, or a combination of the two. Currently, however, a variety of options are available.
Formerly, glucose syrup was only produced by combining corn starch with dilute hydrochloric acid
, and then heating the mixture under pressure. Currently, glucose syrup is mainly produced by first adding the enzyme
α-amylase
to a mixture of corn starch and water. α-amylase is secreted by various species of the bacterium
Bacillus
; the enzyme is isolated from the liquid in which the bacteria are grown. The enzyme breaks the starch into oligosaccharide
s, which are then broken into glucose molecules by adding the enzyme glucoamylase, known also as "γ-amylase". Glucoamylase is secreted by various species of the fungus
Aspergillus
; the enzyme is isolated from the liquid in which the fungus is grown. The glucose can then be transformed into fructose by passing the glucose through a column that is loaded with the enzyme D-xylose isomerase
, an enzyme that is isolated from the growth medium of any of several bacteria.
(an ingredient that retains moisture and thus maintains a food's freshness). Glucose syrup is also widely used in the manufacture of a variety of candy products.
In the United States, cane sugar quotas raise the price of sugar; hence, domestically produced corn syrup and high-fructose corn syrup (HFCS) are less expensive alternatives that are often used in American-made processed and mass-produced foods, candies, soft drinks and fruit drinks to help control cost.
Glucose syrup was the primary corn sweetener in the United States prior to the expanded use of HFCS production. HFCS is a variant in which other enzymes are used to convert some of the glucose into fructose. The resulting syrup is sweeter and more soluble. Corn syrup is also available as a retail product.
Syrup
In cooking, a syrup is a thick, viscous liquid consisting primarily of a solution of sugar in water, containing a large amount of dissolved sugars but showing little tendency to deposit crystals...
, made from the hydrolysis
Hydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
of starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
. Maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
is commonly used as the source of the starch in the USA, in which case the syrup is called "corn syrup
Corn syrup
Corn syrup is a food syrup, which is made from the starch of maize and contains varying amounts of maltose and higher oligosaccharides, depending on the grade. Corn syrup is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor...
", but glucose syrup is also made from other starch crops, including potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
es, wheat
Wheat
Wheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
, barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...
, rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
and cassava
Cassava
Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...
p.21. Glucose syrup containing over 90% glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
is used in industrial fermentation
Fermentation (food)
Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...
p.230, but syrups used in confectionery
Confectionery
Confectionery is the set of food items that are rich in sugar, any one or type of which is called a confection. Modern usage may include substances rich in artificial sweeteners as well...
manufacture contain varying amounts of glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
, maltose
Maltose
Maltose , or malt sugar, is a disaccharide formed from two units of glucose joined with an αbond, formed from a condensation reaction. The isomer "isomaltose" has two glucose molecules linked through an α bond. Maltose is the second member of an important biochemical series of glucose chains....
and higher oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...
s, depending on the grade, and can typically contain 10% to 43% glucose.p.132 Glucose syrup is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor. By converting some of the glucose in corn syrup into fructose
Fructose
Fructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...
(using an enzymatic
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
process), a sweeter product, high-fructose corn syrup can be produced.
Types of glucose syrup
Depending on the method used to hydrolyse the starch and on the extent to which the hydrolysis reaction has been allowed to proceed, different grades of glucose syrup are produced, which have different characteristics and uses. The syrups are broadly categorised according to their dextrose equivalentDextrose equivalent
Dextrose equivalent is a measure of the amount of reducing sugars present in a sugar product, relative to glucose, expressed as a percentage on a dry basis. For example, a maltodextrin with a DE of 10 would have 10% of the reducing power of dextrose , while sucrose, with a DE of 120, would have...
(DE). The further the hydrolysis process proceeds, the more reducing sugars are produced, and the higher the DE. Depending on the process used, glucose syrups with different compositions, and hence different technical properties, can have the same DE.
Confectioner's syrup
The original glucose syrups were manufactured by acid hydrolysis of corn starch at high temperature and pressure. The typical product had a DE of 42, but quality was variable due to the difficulty of controlling the reaction. Higher DE syrups made by acid hydrolysis tend to have a bitter taste and a dark colour, due to the production of hydroxymethylfurfuralHydroxymethylfurfural
Hydroxymethylfurfural , also 5-furfural, is an organic compound derived from dehydration of certain sugars. This yellow low-melting solid is highly water-soluble. The molecule consists of a furan ring, containing both aldehyde and alcohol functional groups...
and other byproducts.p.26 This type of product is now manufactured using a continuous process and is still widely used due to the low cost of acid hydrolysis. The sugar profile of a confectioner's syrup can also be mimicked by enzyme hydrolysis. A typical confectioner's syrup contains 19% glucose, 14% maltose, 11% maltotriose
Maltotriose
Maltotriose is a trisaccharide consisting of three glucose molecules linked with α-1,4 glycosidic bonds.It is most commonly produced by the digestive enzyme alpha-amylase on amylose in starch...
and 56% higher molecular mass
Molecular mass
The molecular mass of a substance is the mass of one molecule of that substance, in unified atomic mass unit u...
carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
s.p.464
High-maltose glucose syrups
By using β-amylase or fungal α-amylaseAlpha-Amylase
α-Amylase is an enzyme that hydrolyses alpha-bonds of large alpha-linked polysaccharides such as starch and glycogen, yielding glucose and maltose. It is the major form of amylase found in humans and other mammals...
, glucose syrups containing over 50% maltose, or even over 70% maltose (extra-high-maltose syrup) can be producedp.465. This is possible because these enzymes remove two glucose units (i.e. one maltose molecule) at a time from the end of the starch molecule. High-maltose glucose syrup has a great advantage in the production of hard candy: at a given moisture level and temperature, a maltose solution has a lower viscosity than a glucose solution, but will still set to a hard product. Maltose is also less humectant than glucose, so that candy produced with high-maltose syrup will not become sticky as easily as candy produced with a standard glucose syrupp.81.
Commercial preparation
Irrespective of the feedstock or the method used for hydrolysis, certain steps are common to the production of glucose syrup:Preparation
Before conversion of starch to glucose can begin, the starch must be separated from the plant material. This includes removing fibre and protein (which can be valuable by-products, for example wheat or maize glutenGluten
Gluten is a protein composite found in foods processed from wheat and related grain species, including barley and rye...
.p.22) Protein produces off-flavours and colours due to the Maillard reaction
Maillard reaction
The Maillard reaction is a form of nonenzymatic browning similar to caramelization. It results from a chemical reaction between an amino acid and a reducing sugar, usually requiring heat....
, and fibre is insoluble and has to be removed to allow the starch to become hydrated. The plant material also needs to be ground as part of this process to expose the starch to the water.
Soaking
The starch needs to be swelled to allow the enzymes or acid to act upon it. When grain is used, sulfur dioxideSulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
is added to prevent spoilage.
Gelatinisation
By heating the ground, cleaned feedstock, starch gelatinizationStarch gelatinization
Starch gelatinization is a process that breaks down the intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen bonding sites to engage more water. This irreversibly dissolves the starch granule...
takes place: the intermolecular bonds of the starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
molecules are broken down, allowing the hydrogen bond
Hydrogen bond
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...
ing sites to engage more water. This irreversibly dissolves the starch granule
Granule (cell biology)
In cell biology, a granule is a small particle. It can be any structure barely visible by light microscopy. The term is most often used to describe a secretory vesicle.-Leukocytes:...
, so that the chains begin to separate into an amorphous form. This prepares the starch for hydrolysis.
Hydrolysis
Glucose syrup can be produced by acid hydrolysisAcid hydrolysis
Acid hydrolysis is a chemical process in which acid is used to convert cellulose or starch to sugar.It implies a chemical mechanism of hydrolysis catalyzed by a Brønsted-Lowry or Arrhenius acid. By contrast, it does not usually imply hydrolysis by direct electrophilic attack—as may originate from...
, enzyme hydrolysis, or a combination of the two. Currently, however, a variety of options are available.
Formerly, glucose syrup was only produced by combining corn starch with dilute hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
, and then heating the mixture under pressure. Currently, glucose syrup is mainly produced by first adding the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
α-amylase
Amylase
Amylase is an enzyme that catalyses the breakdown of starch into sugars. Amylase is present in human saliva, where it begins the chemical process of digestion. Food that contains much starch but little sugar, such as rice and potato, taste slightly sweet as they are chewed because amylase turns...
to a mixture of corn starch and water. α-amylase is secreted by various species of the bacterium
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
Bacillus
Bacillus
Bacillus is a genus of Gram-positive, rod-shaped bacteria and a member of the division Firmicutes. Bacillus species can be obligate aerobes or facultative anaerobes, and test positive for the enzyme catalase. Ubiquitous in nature, Bacillus includes both free-living and pathogenic species...
; the enzyme is isolated from the liquid in which the bacteria are grown. The enzyme breaks the starch into oligosaccharide
Oligosaccharide
An oligosaccharide is a saccharide polymer containing a small number of component sugars, also known as simple sugars...
s, which are then broken into glucose molecules by adding the enzyme glucoamylase, known also as "γ-amylase". Glucoamylase is secreted by various species of the fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
Aspergillus
Aspergillus
Aspergillus is a genus consisting of several hundred mold species found in various climates worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli...
; the enzyme is isolated from the liquid in which the fungus is grown. The glucose can then be transformed into fructose by passing the glucose through a column that is loaded with the enzyme D-xylose isomerase
Xylose isomerase
In enzymology, a xylose isomerase is an enzyme that catalyzes the chemical reactionThis enzyme belongs to the family of isomerases, specifically those intramolecular oxidoreductases interconverting aldoses and ketoses. The systematic name of this enzyme class is D-xylose aldose-ketose-isomerase...
, an enzyme that is isolated from the growth medium of any of several bacteria.
Clarification
After hydrolysis, the dilute syrup can be passed through columns to remove impurities, improving its colour and stability.Evaporation
The dilute glucose syrup is finally evaporated under vacuum to raise the solids concentration.Uses
Its major uses in commercially-prepared foods are as a thickener, sweetener, and humectantHumectant
A humectant is a hygroscopic substance. It is often a molecule with several hydrophilic groups, most often hydroxyl groups, but amines and carboxyl groups, sometimes esterified, can be encountered as well; the affinity to form hydrogen bonds with molecules of water is crucial here.Since...
(an ingredient that retains moisture and thus maintains a food's freshness). Glucose syrup is also widely used in the manufacture of a variety of candy products.
In the United States, cane sugar quotas raise the price of sugar; hence, domestically produced corn syrup and high-fructose corn syrup (HFCS) are less expensive alternatives that are often used in American-made processed and mass-produced foods, candies, soft drinks and fruit drinks to help control cost.
Glucose syrup was the primary corn sweetener in the United States prior to the expanded use of HFCS production. HFCS is a variant in which other enzymes are used to convert some of the glucose into fructose. The resulting syrup is sweeter and more soluble. Corn syrup is also available as a retail product.