Physical Properties
Recommended Separation Techniques
Ranked by effectiveness for glucose recovery from starch hydrolysates and fermentation broths.
Glucose crystallizes as dextrose monohydrate (C₆H₁₂O₆·H₂O) below 50°C from supersaturated solutions (>300 g/L). Multi-stage cooling crystallization with seeding yields 99.5%+ purity. Anhydrous β-D-glucose crystallizes above 50°C. Industrial standard for pharmaceutical and food-grade glucose.
Strong acid cation exchange resin (Ca²+ form) separates glucose from fructose based on differential complexation with calcium ions. Fructose forms stronger Ca²+ complexes and elutes later. Industrial scale: 10–100 m³/hr feed. Essential for high-fructose corn syrup (HFCS) production.
NF membranes (150–300 Da MWCO) retain glucose (180 Da) at 85–95% rejection while passing salts, organic acids, and water. Useful for concentrating and demineralizing glucose syrups. Diafiltration further improves purity. Energy-efficient alternative to evaporation for pre-concentration.
Granular or powdered activated carbon removes color bodies, HMF (5-hydroxymethylfurfural), and organic impurities from glucose syrups by adsorption. Standard polishing step before crystallization. Does not separate glucose from other sugars but essential for color grade specification.
Common Impurity Separations
| Separate From | Key Difference | Best Technique | Selectivity Basis |
|---|---|---|---|
| Fructose | Ca²+ complexation (same MW) | SMB Chromatography (Ca²+) | Differential ligand exchange |
| Sucrose | MW (180 vs 342 Da) | NF / Size Exclusion | Molecular weight difference |
| Salts (NaCl) | Size (180 Da vs 58 Da, both neutral/ionic) | NF (300 Da MWCO) | MW cutoff + Donnan exclusion |
| Proteins | MW (180 Da vs >10 kDa) | UF (10 kDa MWCO) | Molecular weight cutoff |
Anomeric Forms & Mutarotation
Glucose exists in equilibrium between multiple forms in solution, which affects crystallization and chromatographic behavior.
Solution Equilibrium
In aqueous solution, D-glucose equilibrates between α-pyranose (36%), β-pyranose (64%), and trace amounts of open-chain and furanose forms. This mutarotation reaches equilibrium in 2–4 hours at 25°C (faster at higher temperatures or with acid/base catalysis).
Impact on Separation
| Property | α-D-Glucose | β-D-Glucose | Separation Impact |
|---|---|---|---|
| Specific rotation | +112.2° | +18.7° | Optical purity measurement |
| Crystallization | Below 50°C (monohydrate) | Above 50°C (anhydrous) | Temperature controls crystal form |
| Solubility (25°C) | 830 g/L | 1,500 g/L | α-form crystallizes preferentially |
| Ca²+ affinity | Weaker | Stronger | Affects SMB elution profile |
Frequently Asked Questions
How is glucose separated from fructose in HFCS production?
Simulated moving bed (SMB) chromatography using Ca²+-form strong acid cation exchange resin is the industry standard. Fructose forms stronger complexation with Ca²+ ions, eluting later than glucose. This produces a fructose-enriched stream (90% fructose) and a glucose-rich raffinate. Design sugar separation processes with untangle.bio.
What is dextrose monohydrate crystallization?
Concentrated glucose syrup (70–75 Brix) is seeded with dextrose monohydrate crystals and slowly cooled from 45°C to 25°C over 3–5 days in crystallizers. The α-D-glucose monohydrate crystals (C₆H₁₂O₆·H₂O) are separated by centrifugation, washed, and dried. Purity: 99.5–99.9%.
Can NF membranes separate glucose from fructose?
No. Glucose and fructose are structural isomers with identical molecular weights (180.16 Da), so NF membranes cannot distinguish them. Separation requires property-specific methods like SMB chromatography (Ca²+ affinity), enzymatic conversion, or selective crystallization.
How do you remove color from glucose syrups?
Activated carbon (powdered or granular) adsorbs color bodies (melanoidins, HMF, caramel compounds) from glucose syrups. Typical treatment: 0.5–2% w/v carbon at 70–80°C for 30 minutes, followed by filtration. Ion exchange with mixed-bed resins provides additional decolorization and demineralization.
Related Molecules
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