History. The discovery of the New World increased the import and use of sugar extracted from sugar cane, particularly from plantations in the West Indies. During the Napoleonic Wars, imports were temporarily interrupted. This situation may have indirectly encouraged G. Kirchhoff to develop a process for producing a sugar substitute from starch.
In 1811, Kirchhoff published a method for the acid hydrolysis of starch. Since then, the process has been continuously modified and improved. These developments eventually led to the production of some of the most versatile starch-based sweeteners used by the food and chemical industries today.
The Second World War created another shortage of sweeteners and encouraged further advances in starch processing. One important development was the invention of the continuous glucose converter by Karl Kroyer of Denmark. Members of The International Starch Group were closely involved in the development and industrial application of this technology, including the introduction of enzymes for glucose hydrolysis and the development of new products such as Total Sugar.
Starch Chemistry and Glucose Formation
Glucose is naturally formed in plants from carbon dioxide absorbed from the air, using sunlight as an energy source. Part of this glucose is polymerised into long chains and stored in starch granules as an energy reserve. When new growth begins, plants break down the stored starch to provide energy.
This natural breakdown of starch can be reproduced in industrial processing by applying acids or enzymes to cooked starch. The process causes starch to hydrolyse into different mixtures of glucose and intermediate sugars. These mixtures are characterised using the Dextrose Equivalent (DE) value.
The DE value indicates the degree of starch conversion. Pure starch is assigned a DE of 0, while pure glucose, also known as dextrose, has a DE of 100. As starch is hydrolysed, its DE increases and the resulting syrup contains a greater proportion of smaller sugar molecules.
What Is Dextrose Equivalent?
Dextrose Equivalent is an important measurement in starch and sweetener processing. It helps manufacturers describe the degree to which starch has been converted into glucose and other sugars.
- DE 0 represents pure starch.
- Intermediate DE values indicate partially hydrolysed starch containing glucose and other sugar molecules.
- DE 100 represents pure glucose or dextrose.
The DE value also affects the physical characteristics, sweetness, crystallisation behaviour and industrial applications of starch-based syrups.
Crystallised Glucose and Dextrose Monohydrate
Only glucose solutions with a high DE can crystallise easily and produce a powder or granular product. One of the most widely used crystallised products is dextrose monohydrate, which is essentially pure glucose.
Dextrose monohydrate has applications in medicine and is also used in chewing tablets for people involved in sports. Another less purified product is known as Total Sugar. It can be produced by rapidly crystallising a 97 DE syrup while avoiding the disposal of a separate mother liquor.
Standard 42 DE Glucose Syrup
As the DE value decreases, a glucose syrup gradually loses its tendency to crystallise. Below approximately 45 DE, the syrup can be evaporated into a stable, non-crystallising and effectively self-sterile liquid. These characteristics help explain the widespread use of standard 42 DE glucose syrup.
Starch is hydrolysed by acid or enzymes to approximately 40–42 DE and then evaporated until the syrup reaches a dry matter content of around 80–84%. The resulting syrup has a mild, sweet taste and can be stored and transported in drums or tank trucks.
Applications of 42 DE Syrup
Standard 42 DE syrup is used in a wide range of food and industrial applications, including:
- canned fruit and fruit preserves;
- ice cream;
- bakery products;
- jam;
- soft drinks;
- candy and confectionery products; and
- alcohol fermentation as a carbohydrate booster.
The relative sweetness of 42 DE syrup compared with sucrose is approximately 40–45%.
How 42 DE Glucose Syrup Is Produced
The production process begins with high-quality starch. The starch can be supplied as a slurry directly from a starch factory or prepared from ordinary native dried starch at approximately 21 °Bé.
The main production stages can be summarised as follows:
- Prepare the starch slurry.
- Add acid, preferably hydrochloric acid (HCl), to acidify the slurry.
- Heat the acidified slurry to the required temperature using steam.
- Maintain the liquefaction temperature for several minutes.
- Control the degree of hydrolysis through the temperature in the holding zone.
- Neutralise the acid after the required degree of conversion has been reached.
- Pass the hydrolysate through a cyclone using a back-pressure valve.
- Refine the crude hydrolysate using activated carbon to remove discoloration.
- Add filter aid and remove suspended material using a filter press.
- Pass the purified hydrolysate through a check filter.
- Evaporate the clear hydrolysate until the dry matter reaches approximately 80–84%.
- Transfer the final product into drums or other suitable storage systems.
Depending on the raw material and final product requirements, additional filtration, demineralisation and ion-exchange stages may be incorporated into the process.
Enzymes as Catalysts in Starch Conversion
Acid catalysts can be used to manufacture intermediate conversion products ranging from approximately 35 to 55 DE. However, enzymes can also be used to produce intermediate and high-conversion products for specialised applications.
Enzymatic starch conversion is typically carried out in two main stages. The first stage is liquefaction, while the second stage is saccharification.
- Liquefaction: thermostable alpha-amylase or acid is used to break down the starch.
- Cooling and pH adjustment: the hydrolysate is prepared for the next enzymatic reaction.
- Saccharification: an enzyme such as amyloglucosidase converts the hydrolysed starch into smaller sugars.
Although the basic process is similar, acids and enzymes break down starch differently. As a result, two syrups with the same DE value may have different sugar compositions. Nevertheless, the process can be adjusted to produce a classic 42 DE syrup using an entirely enzymatic process.
Enzymatic processing also makes it possible to produce syrups with DE values ranging from approximately 28 to 98.
Glucose Syrup Conversion Groups
| Conversion | DE |
|---|---|
| Low | 20–38 |
| Intermediate | 38–58 |
| High | 58–73 |
| Very high | 73 and above |
Glucose Composition at Different DE Values
| Component | DE 28 | DE 38 | DE 42 | DE 63 | DE 98 |
|---|---|---|---|---|---|
| Catalyst | A/E | A | A | A/E | E |
| Glucose | 5 | 12 | 18 | 37 | 96 |
| Maltose | 8 | 10 | 13 | 34 | 2 |
| Maltotriose | 16 | 10 | 12 | 16 | 1 |
| Higher sugars | 71 | 68 | 57 | 13 | 1 |
A = Acid; E = Enzyme; A/E = Acid liquefaction plus enzyme saccharification.
High DE Glucose Syrups and Their Uses
High DE syrups are important intermediates for producing fructose syrup, sorbitol and various fermentation products. They are also used in beverages and food products.
Glucose syrup and maltose syrup are also used in breweries as wort syrups. In this application, they can substitute for malt while helping manufacturers adjust production capacity, protein levels, taste and mouthfeel.
Water Activity in Sweeteners
Sugar confectionery can either absorb moisture from the atmosphere or lose moisture to the surrounding environment. The behaviour depends on external conditions and the characteristics of the sweetener.
For this reason, water activity is an important property when evaluating sweeteners. The source refers to this relationship using equilibrium relative humidity (ERH).
Water Activity of Selected Sweeteners
| Syrup | Conversion | Solids | Water Activity |
|---|---|---|---|
| 42 DE | A | 75 | 0.81 |
| 42 DE | A | 80 | 0.77 |
| 42 DE | A | 85 | 0.70 |
| 60 DE | A/E | 75 | 0.78 |
| 60 DE | A/E | 80 | 0.71 |
| 60 DE | A/E | 85 | 0.64 |
| 94 DE | E | 74 | 0.72 |
| High Fructose | E | 70 | 0.76 |
| Liquid Sucrose | — | 67 | 0.85 |
High Fructose Starch-Based Syrups
HFSS (High Fructose Starch-based Syrups) are produced from refined, very high DE glucose syrups. The conversion of glucose into fructose is carried out enzymatically using isomerase fixed on a resin.
The use of multiple resin columns in parallel allows the enzyme activity to be managed efficiently before the resin is replaced or regenerated.
HFSS-42 and HFSS-55
The isomerase enzyme catalyses the formation of approximately 42% fructose in equilibrium with glucose. The resulting syrup can be refined and evaporated for use as a general-purpose sweetener.
To obtain a closer match with liquid sugar based on sucrose from sugar cane or sugar beet, the fructose concentration can be increased to approximately 55%. The HFSS-42 stream is fractionated into fructose and glucose, with chromatography providing an efficient method for this separation.
The fructose fraction is then blended back with HFSS-42 to produce HFSS-55. This product provides a composition closer to traditional sucrose-based liquid sugar and has widespread applications as a sweetener in soft drinks.
HFSS-90
The fructose fraction obtained from the chromatographic column can also be refined and evaporated separately to produce HFSS-90. According to the source, this high-fructose syrup can be used in low-calorie food products.
Demineralisation during the HFSS process and precautions against de-cross-linking caused by oxygen can extend the useful lifetime of the resin. For efficient operation, an HFSS section is preferably operated continuously.
Starch and Sweetener Production Process
The overall production route begins with agricultural raw materials such as corn, cassava and potato. These materials are processed into native starch before further conversion into granular starch products or hydrolysed starch products.
- Raw material processing: corn is cleaned and steeped, while cassava and potato are washed and rasped.
- Separation and extraction: starch is separated from the raw material and extracted.
- Concentration: the extracted starch is concentrated.
- Refining: the starch is further refined to produce purified starch milk.
- Slurry preparation: purified starch milk is prepared for conversion.
- Liquefaction: starch is partially hydrolysed using acid or enzymes.
- Saccharification: enzymes further convert the hydrolysate into smaller sugars.
- Refining and ion exchange: impurities and minerals are removed according to the desired product specification.
- Evaporation: the product is concentrated to the required solids level.
- Crystallisation, separation, drying or finishing: further processing depends on the final starch or sweetener product.
Major Products from the Starch Conversion Process
- Native corn starch
- Native tuber starch
- Modified starch
- Maltodextrin
- Dextrose monohydrate
- Sorbitol
- HFSS-55
- HFSS-42
- High DE glucose syrup
- Glucose syrup
Starch as a Versatile Raw Material for Sweeteners
The development of starch hydrolysis has transformed starch from a plant storage material into a versatile industrial raw material. Through acid hydrolysis, enzymatic conversion, refining, evaporation and other processing stages, starch can be converted into products with different DE values and functional characteristics.
These products serve a wide range of industries, particularly food and beverage manufacturing. The ability to control the degree of conversion allows manufacturers to obtain sweeteners and starch derivatives with specific sweetness, viscosity, crystallisation behaviour and moisture characteristics.
Cassava is one of the important sources of starch that can enter this processing chain alongside corn and potato. Its starch can be refined and converted into various starch-based products, including glucose syrups and other sweetener intermediates.
Key Points About Starch-Based Sweeteners
- Starch can be hydrolysed using acids, enzymes or a combination of both.
- The degree of starch conversion is expressed through the Dextrose Equivalent (DE) value.
- Pure starch has a DE of 0, while pure glucose has a DE of 100.
- 42 DE glucose syrup is a stable, non-crystallising syrup widely used in food applications.
- Enzymatic processing can produce syrups with DE values ranging from approximately 28 to 98.
- High DE glucose syrups can serve as intermediates for fructose syrup, sorbitol and fermentation products.
- High fructose starch-based syrups are produced through enzymatic conversion of glucose into fructose.
- Starch processing can produce both granular starch products and hydrolysed starch products.
Conclusion
The history of starch sweeteners shows how advances in starch processing have expanded the uses of agricultural raw materials. From the early development of acid hydrolysis to modern enzymatic conversion, starch can now be processed into a wide range of sweeteners and functional ingredients.
The Dextrose Equivalent (DE) provides an important way to classify the degree of starch conversion and helps determine the characteristics and applications of the resulting syrup. Low, intermediate and high DE products can serve different industrial purposes, while highly converted syrups can be further processed into fructose-based sweeteners.
With sources such as corn, cassava and potato available for starch production, the starch industry continues to provide raw materials for food, beverage, fermentation and other applications. Cassava starch, in particular, forms part of this broader starch processing chain and can be converted into products with specific industrial functions.