Corn Sweetener Refining with Ion Exchange Resins

Liquid and solid sweeteners are produced around the world from several starch sources including corn, wheat, tapioca, potatoes, and even cellulose hydrolyzate. Of these, corn is the most common. There are nearly one billion bushels of corn processed for sweeteners in the U.S. alone. High fructose corn syrup (HFCS) is the largest single sweetener syrup produced.

HFCS is found in canned fruits, cereals, chemicals, drugs, pharmaceuticals, condiments, confectionery items, gum, cough drops, dairy products, ice cream, frozen desserts, jellies, meat products and carbonated beverages. Ion exchange resins are utilized in the demineralization, enrichment and polishing/decolorization unit operations of HFCS refining to produce a pure colorless syrup having the desired sugar profile.

HFCS, the most highly refined of the liquid corn sweeteners, is produced in a corn wet milling process which includes the following unit operations:

  1. Steeping: Corn kernels soak in sulfurous acid to soften them.
  2. Germ Separation: Kernels are fractured into starch, gluten, hull and germ components. The oil rich germ is separated and processed for oil extraction.
  3. Fiber Recovery: The slurry of starch, gluten and hull is finely ground and the hull is separated.
  4. Starch/Gluten Separation: Starch and gluten are separated in centrifuges and each is washed.
  5. Liquefaction: The solid starch particles are liquefied by enzymatic breakdown into dextrins — partially degraded starch chains.
  6. Saccharification: Dextrins are enzymatically hydrolyzed into soluble mono-, di-, tri and oligosaccharides.
  7. Filtration: Diatomaceous earth or membrane filters remove retrograde starch, oil, proteins or other insoluble material.
  8. Decolorization: Carbon removes color, flavor and odor compounds from filtered syrup. 
  9. Demineralization: Ion exchange resins remove ash, protein, organic acids and color from the corn sweetener to provide color and flavor stability.
  10. Adsorbent resins can be used in lieu of carbon after ion exchange for color, taste and odor removal.
  11. Isomerization: Dextrose is enzymatically isomerized to fructose (42% fructose or 42 HFCS) for increased sweetness.
  12. Demineralization: Ion exchange resins remove color and the salts which were added to facilitate isomerization.
  13. Adsorbent resins can be used in lieu of carbon after ion exchange for color, taste and odor removal.
  14. Evaporation: Dilute syrup is concentrated by evaporation of water.
  15. Chromatographic Separation: Fructose/dextrose mixture (42 HFCS) is separated with a chromatographic separation resin to produce a fructose rich (90% fructose or 90 HFCS) stream and dextrose rich stream.
  16. Polishing/Decolorization: Color, hydroxymethylfurfural (HMF) and residual ash are removed with ion exchange resins from the fructose rich product before or after blending to 55 HFCS.
  17. Evaporation: 55 HFCS product is concentrated prior to shipment by evaporation of water.

Ion exchange resins are utilized in the demineralization, enrichment and polishing/decolorization unit operations of HFCS refining as described below to produce a pure colorless syrup having the desired sugar profile.

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