How To Grow Fructose Crystals

Easy To Grow Fruit Sugar Crystals

This is a map of the electrostatic potential of a fructose molecule.
This is a map of the electrostatic potential of a fructose molecule. PASIEKA, Getty Images

Fructose or fruit sugar is a monosaccharide that you can buy at a grocery store. It's also found in high-fructose corn syrup, honey, sugar cane, fruit, molasses, and maple syrup. You grow crystals of this sugar in much the same way as you would grow table sugar or sucrose crystals, so you can compare the crystal structures of different carbohydrates.

Fructose Crystal Materials

  • fructose (C6H12O6)
  • water
  • food coloring (optional)

Although fructose has the same chemical formula as glucose, it has a different structure. It is more soluble in water than sucrose or glucose, so it is a little harder to crystallize out of solution. However, the basic preparation is the same for all the sugars and sugar alcohols, so if you can grow regular sugar crystals, you can grow fructose crystals.

Procedure

  1. Mix an 80% solution of fructose in boiling water. As with regular sugar crystals, one way to get a saturated solution is to keep adding sugar into boiling water until no more will dissolve.
  2. If you want colored crystals, you can add a drop or more of food coloring to the solution.
  3. If you just place this solution in an undisturbed location at room temperature, fructose crystals will form spontaneously, but it could take a couple of weeks. A much quicker and easier way to grow fructose crystals is to sprinkle a small amount of fructose powder onto the surface of the liquid and to refrigerate it. The lower temperature lowers the solubility of fructose in water, so it can form crystals more readily. The tiny fructose crystals (the powder) provide a surface for crystals to grow.
  1. Small white, woolly-looking splotches will appear on the top of the solution. These are masses of fine crystals of fructose hemihydrate (C6[H2O]6 · ½H2O). You can observe their structure using a magnifying glass or microscope. Assuming you don't want fine, hairlike crystals, what you need to do is stir these spots into the solution. Stirring breaks the hemihydrate crystals so you can grow crystals of fructose dihydrate (C6[H2O]6 · 2H2O).
  1. Give the crystals time to grow. When you are pleased with the appearance of the crystals, you can remove them from the solution. As with ordinary sugar crystals, these are safe to eat, although you can't eat fructose in large amounts like you can ordinary table sugar.

Tips for Success

  • The biggest key to success is getting a saturated solution. A lot of fructose dissolves in water, so it's a good idea to start with a small amount of water and to use a wide-mouth jar. That way, if the solution isn't saturated, evaporation can help solve concentration the solution.
  • Use temperature to your advantage. More sugar dissolves as temperature increases, so you boiling water to dissolve the solution. On the flip side, solubility decreases as temperature drops, so you can lower the temperature of the solution to help crystals start to grow.
  • Once you see crystal growth, you can remove that crystal, place it in a new container, and pour the solution onto it. This crystal will serve as a 'seed' for crystal growth and changing containers will help ensure tiny crystals growing on the original jar won't compete with your seed for growth.
  • If you prefer, you can grow fructose crystals from high-fructose corn syrup. This liquid isn't saturated, so you'll need to either boil off some water or else allow plenty of time for water to evaporate out of the liquid.