Waking up yeast
Yeast is a living fungus that eats sugar and gives off carbon dioxide, which puffs up dough. It works best at 25 to 35°C (77 to 95°F). Above about 55°C (130°F) it dies, and in the cold it slows to almost nothing.
Slow rises taste better
A cold rise in the fridge for 12 to 72 hours slows the yeast but keeps producing flavor compounds, so the bread tastes deeper and slightly tangy. A fast rise in a warm kitchen takes 1 to 2 hours and gives a plainer flavor.
Test yourself
Questions from the interactive lesson, with the answer and the why.
You're activating dry yeast. What water temperature is best?
Comfortably warm, about 40°C (105°F). Water that feels warm but not hot activates yeast without harming it.
True or false: If active dry yeast shows no foam after 10 minutes in warm sugar water, it is probably dead.
True. Foam is carbon dioxide from live yeast, so no foam after 10 minutes means the yeast is dead.
What went wrong? You mix yeast with boiling water and flour. The dough never rises.
The boiling water killed the yeast. Yeast dies above about 55°C (130°F), so the water must be warm, not hot.
Fill the blank: Yeast eats sugar and gives off ___ gas, which gluten traps to puff up the dough.
Yeast eats sugar and gives off carbon dioxide gas, which gluten traps to puff up the dough. Gluten traps it in bubbles that puff up the dough.
You leave the salt out of a loaf. What happens?
It rises too fast and the bread tastes flat. Salt slows yeast and strengthens gluten, so skipping it gives fast, bland bread.
Warm vs cold yeast starter
Wake up the yeast.
Do the 20-minute experiment