Industries
Starch & sweeteners
Process description for sweetener production
DSSE’s process technology comprises process and plant design for maximum utilisation of the starch from the raw materials — for example maize (corn), wheat, potato, tapioca or rice — for conversion into a number of final sweetener products.
Starch processing implies hydrolysis, i.e. partial or total splitting of the long starch molecules into smaller fragments by chemical or enzymatic processes, purification, concentration and other unit operations for obtaining the required sweetener product. The processes as well as the equipment are designed with respect to the type of raw material and final product specification.
Production steps
Sweetener production is a combination of key process steps
01
Liquefaction
The first process step in a sweetener plant. It comprises a gelatinisation of the starch molecules, facilitating the break-down into smaller molecular fragments. This effect is today mainly obtained by adding enzymes to the starch slurry prior to heat treatment with direct steam injection, and by means of reactors to ensure correct reaction conditions.
02
Saccharification
A further enzymatic hydrolysis of the liquefied starch product. The process requires equipment for pH and temperature adjustment and holding tanks for obtaining the required degree of saccharification. Lower degrees of hydrolysis are achieved by inactivation of the enzymes after a certain reaction time. The saccharified and inactivated product requires refining to remove impurities such as proteins, fibres, fat and soluble components.
03
Vacuum filtration
A rotary vacuum drum filter with a precoat layer of diatomaceous earth or similar filter aid is normally used. Insoluble protein and solid impurities are removed during this filtration.
04
Membrane filtration
Based on the cross-flow principle, using ceramic or polymer membranes of very small pore size. It can be used as an alternative to traditional precoat vacuum filtration. The advantages include the non-necessity of precoat material and a better-refined substrate.
05
Carbon treatment
Activated carbon adsorbs colour, proteins and other undesired components from the hydrolysate. The powdered carbon is added by a dust-tight metering system, and the spent carbon is retained in a vertical candle filter. The alternative is a granulated carbon treatment system, where the hydrolysate passes through a fixed bed column of granulated carbon that can be regenerated after exhaustion.
06
Ion exchange
After protein filtration and carbon treatment, further refining is achieved by ion exchange. Cations, anions, amino acids and a number of colouring substances are removed in fixed bed columns filled with cation and anion resins. Single pass, double pass and/or mixed bed solutions can be used. When exhausted, the resin beds are regenerated in-situ with hydrochloric acid and sodium hydroxide. The total operation can be controlled automatically.
07
Concentration by evaporation
Raises the solids content of the hydrolysate. Single or multi-effect falling film or plate evaporators are used, applying either thermal or mechanical vapour re-compression. Malto-dextrin or glucose syrup solids are concentrated to a DS suitable for spray drying; glucose, maltose or liquid dextrose syrups are evaporated to the desired DS content (typically 70–80%); dextrose monohydrate, anhydrous dextrose, fructose syrup or sorbitol are concentrated to the DS required for further processing.
08
Crystallisation
Cooling crystallisation is used for the production of dextrose monohydrate. The crystallizers can be of vertical or horizontal design, equipped with agitators and cooling facilities. For anhydrous dextrose, an automatically controlled vacuum crystallizer is used as a second crystallisation step.
09
Isomerization
A process for converting glucose into fructose, thereby increasing the sweetness of the product. The fixed bed iso-columns containing the immobilised isomerisation enzyme are operated at conditions selected to achieve the specified isomerisation.
10
Fractionation
To increase the fructose content of the isomerized dextrose syrup, a chromatographic separation of fructose and dextrose is carried out. The solution passes through a column filled with a special resin, separating it into a fructose fraction and a dextrose fraction.
11
Hydrogenation
Sorbitol and other polyols are produced by catalytic hydrogenation of a refined dextrose hydrolysate, using special reactors designed for high pressure and temperature operation. The reactors are equipped with heating/cooling facilities and an effective agitating system.
12
Fluid bed drying
Air is passed through a bed of particles so that a state of fluidization occurs. Fluid bed dryers are selected as best capable of handling the particulate structure of crystalline sweetener products.
13
Spray drying
One of the most important continuous drying techniques for converting liquid sweetener formulations into powders. The feed is atomised into droplets directed into a controlled flow of hot air; particles are formed as moisture evaporates, and the dried product is discharged from the drying chamber. Depending on the type of sweetener, various spray dryer designs are selected.