Fructose
Properties
| State | Solid (white crystalline powder) |
| Color | White |
| Solubility | Very soluble in water (3750 g/L at 20°C); soluble in ethanol |
| Melting Point | 103°C |
| Boiling Point | Decomposes before boiling |
About Fructose
Fructose is the ketose member of the hexose pair — same molecular formula as glucose (C6H12O6, 180.156 g/mol), same atoms, but the carbonyl sits at C-2 instead of C-1, making it a ketohexose rather than an aldohexose. That single positional change drives almost everything that distinguishes fructose chemistry: it cyclizes preferentially into the five-membered furanose form (~70% in solution at room temperature) rather than the six-membered pyranose that glucose adopts; it has the strongest sweetening power of any natural sugar at roughly 1.7× sucrose on a per-mass basis; and it gives a positive Seliwanoff test in two minutes versus the slow positive that glucose eventually produces, because the ketose is rapidly dehydrated by HCl to hydroxymethylfurfural. Metabolically, fructose enters glycolysis through fructokinase (KHK) in the liver, bypassing the phosphofructokinase regulatory step that controls glucose flux — which is why a hepatocyte loaded with fructose will shunt carbon into de novo lipogenesis far more readily than the same dose of glucose. The 1990s rise of high-fructose corn syrup as a sucrose substitute in soft drinks (made by isomerizing glucose with immobilized xylose isomerase, then enriching to 55% fructose) is the centerpiece of the metabolic-syndrome literature.
Where you'll encounter it
If you have run a Maillard reaction at the bench and noticed that fructose browns faster than glucose at the same temperature, you are seeing the open-chain ketone form — slightly more reactive electrophilically — react with amine nucleophiles before glucose's aldehyde can keep up. In a clinical chem lab, fructose interferes with the older copper-reduction glucose tests (Benedict's, Clinitest) but not with glucose-oxidase strips, which is the basis for distinguishing essential fructosuria from true diabetes. In a corn-wet-milling plant producing HFCS-55, immobilized xylose isomerase columns running at 60 °C convert glucose-rich syrup to about 42% fructose, then chromatographic enrichment over Ca-form cation-exchange resin lifts the fructose fraction to 55% for soft-drink-grade syrup. In an HMF research lab, fructose dehydration in DMSO with a Brønsted acid at 100 °C gives clean conversion to 5-hydroxymethylfurfural, the bio-renewable platform chemical.
Common Uses
- Tabletop sweetener crystals where extra sweetness allows lower total sugar mass
- High-fructose corn syrup (HFCS-55) sweetener in carbonated soft drinks
- Substrate for hydroxymethylfurfural (HMF) production via acid-catalyzed dehydration
- Inulin-derived fructose stream from chicory root processed for prebiotic fiber
- Diabetic-formulated foods exploiting the lower glycemic index versus glucose
- Parenteral nutrition component in older infusion formulations (now restricted)
- Seliwanoff reagent positive control in undergraduate carbohydrate identification labs
- Cryoprotectant additive in some sperm and embryo vitrification media
Safety Information
GRAS-listed by FDA for food use at typical dietary concentrations. Not classified as hazardous under GHS. Hereditary fructose intolerance (aldolase B deficiency, ~1 in 20,000 births) makes ingestion of even small fructose doses life-threatening — patients develop severe hypoglycemia, lactic acidosis, and hepatic injury within an hour. Fructose malabsorption (much more common, ~30% of adults at high doses) produces gas, bloating, and osmotic diarrhea above ~25 g per sitting. Chronic high intake (>50 g/day from added sweeteners) is associated with non-alcoholic fatty liver disease, hyperuricemia, and dyslipidemia in epidemiological studies. No occupational exposure limit; food-grade dust is a nuisance dust only.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.