Why Does My Homemade Toffee Keep Turning Grainy?

What it means

• Smooth toffee is an amorphous sugar glass, so graininess means the sugar has re-formed into crystals.
• Crystallization is seeded by any stray sugar crystal, whether from undissolved sugar, a dirty spoon, or splashes on the pan wall.
• Rough or rapid agitation and uneven, overly hot cooking can also trigger the sugar to crystallize.

Action steps

1. Dissolve the sugar fully over lower heat before it boils, stirring until you feel no grit.
2. Wash sugar crystals down from the pan sides with a wet pastry brush.
3. Add a little corn syrup (or a few drops of lemon juice or a pinch of cream of tartar) as an interfering agent to inhibit crystallization.
4. Avoid aggressive stirring once it boils; stir gently and steadily.
5. Use a heavy-bottomed pan for even heat and a thermometer to avoid hot spots.

Risks & deadlines

• Once toffee is badly crystallized it usually cannot be rescued and must be recooked; remelting slowly with a little added water sometimes helps but often does not.