Sugar syrup purification


In processing beet sugar, corn sugar and cane sugar, and producing high fructose corn syrup ( HFCS ), ion exchange processes generally are faster, require less energy, and produce less waste than distillation, crystallization, solvent extraction, or other separation methods.

High fructose corn syrup ( HFCS ) is a product of starch sugar processing. There are many types of impurities in sugar solutions and many types of starch sugars, but not much difference in the methods used for refining them.

The typical HFCS process stream includes salts, mineral acids (ash) and organic compounds. These contaminants will interfere with processing and degrade final syrup quality and thus must be removed.

In addition to the desalination and decolorization of sugar solutions, ion exchange resins are also used for the inversion ( hydrolysis ) of disaccharides, particuarly saccharose, and for the treatment of diluted sugary solutions.

The selection of the type of ion exchange technology is critically important.

PuriTech and its ION-IX technology has realised, and can offer a very beneficial technology in following applications :

Demineralization / Deashing :

Demineralization of glucose syrup removes ash, protein and color from the solution. It also increases the long-term color stability of the syrup without the need for addition of sulfur dioxide which can cause a human allergic reaction in the final consumer products.

Deashing typically is performed at two stages in the corn sweetener process, first on the dextrose side and again later on the fructose side.

On the fructose-side (after isomerization ), deashing units perform the same basic function that they did on the dextrose-side. Impurities picked up during isomerization and pH adjustment need to be removed, but overall, there’s a lower non-sugar load than on the dextrose side.

Chromatographic separation :

Different sugars passing through a bed of strong acid cation resin in the calcium or sodium form will separate from one another chromatographically due either to a difference in affinity for the resin or due to different rates of diffusion into and out of the resin beads.

Chromatographic separation resins are functionalized and the beads contain a large amount of water.

A stronger interaction in the fructose/calcium ion complex than in the glucose/calcium ion complex is the basis of the mechanism of separation of fructose from glucose.

This mechanism of separation is called ligand exchange chromatography.

When the syrup stream reaches the chromatographic separation unit process, fructose concentration is approximately 42-45% of dissolved solids. This fructose level is as high as practical using current isomerization enzymes. Using chromatographic separation, fructose concentration can be increased to over 90%.

More commonly, the process is carried out in continuous operating equipment like PuriTech's ION-IX technology.

Beet and cane molasses sucrose recovery processes rely the two most commonly used techniques which are Ion exclusion and ligand exchange.

The separation of dextrose from fructose and polysaccharides rely also on this phenomenon.

Sugar alcohols also demonstrate this behaviour.

Decolorization :

Decolorization units are typically used in the corn sweetener process just before deashing units. Their main purpose is to remove syrup stream components which contribute to color and off-flavors.

Polishing :

Mixed bed polishing is used near the end of the 55 HFCS process to polish the final product and ensure that it meets purity and storage stability requirements.

Softening :

Ion exchange softening has been shown to effectively reduce lime salts in carbonated beet juices, and to reduce evaporator boilouts due to calcium scale deposits.

Also, thin juice softening avoids sedimentation during storage and crystallization of thick juice; and eliminates pre-coat filtration. Thin juice is a good feed material for ion exchange.