What it is.
To fold is to mix gently so you keep the air in. Use a wide spatula. Cut down through the middle, sweep along the bottom, and lift the mix up and over the top. Turn the bowl a little and do it again.
You fold whipped egg whites or cream into a heavier mix, and you fold flour into cake and muffin batter.
Why it works.
Whipped egg whites and whipped cream are full of tiny air bubbles. That air is what makes a mousse light and helps a cake rise. Stirring hard pops the bubbles.
With flour, the reason is gluten. Mixing flour with liquid builds stretchy strands of protein. A little is good. Too much makes muffins and cakes tough and full of tunnels. Folding mixes just enough.
What to look for.
- Stop as soon as the last streak of flour or white is gone.
- The mix still looks puffy and holds its volume.
- A few small lumps in muffin batter are fine.
Common mistakes.
- The mix went flat.
- Fold slowly with a spatula, not a whisk, and stop sooner.
- The whites will not mix into a thick base.
- Stir in a small scoop first to loosen the base. Then fold in the rest.
- Muffins came out tough.
- Fold the flour in with as few strokes as you can.
