More Syrup, Less Downtime: pH Control In Starch Sweetener Deashing

In order to meet purity and storage stability requirements of dextrose (D- glucose) and fructose syrups, ionic impurities are removed in ion exchange columns. Ion exchange resins work by replacing one type of ion for another that has a greater attraction to active sites on the resin polymerK. In syrup deashing, a bed of acidic cation resin is followed by a bed of alkaline anion resin to extract ionic loads made up of salts and mineral acids. In the cation resin, cations such as sodium, potassium, magnesium and calcium are removed. During this exchange step, hydrogen ions are released from the resin. Consequently, there is a significant drop in pH value when the syrup leaves the exchanger. In the down- stream connected anion exchanger, the mineral and organic acids causing low pH are neutralized by the release of hydroxyl ions so that syrup pH is increased again.

Deashing systems consist of two or more unit pairs – the combination of a cation and anion exchanger. One unit pair is in syrup service while another is in the process of being regenerated. Regeneration is necessary when the exchange capability becomes exhausted – this point, called breakthrough, is deter-mined by measuring the syrup pH in the outlet of the exchange columns.