Instant Yeast vs Active Dry Yeast

The difference in one table

	Instant	Active dry
Also sold as	Rapid-rise, quick-rise, bread machine yeast	Active dry, traditional dried yeast
Granule size	Fine	Coarser
How to use	Straight into the dry ingredients	Traditionally dissolved in warm liquid first
Speed	Slightly faster to get going	Slightly slower off the mark
Substituting	1:1 by weight in home recipes

Instant yeast is dried at a lower temperature and milled finer, which means it rehydrates fast enough to be mixed straight into flour. Active dry has larger granules with a layer of dormant cells on the outside, which is why the traditional instruction is to dissolve it first.

How to tell if your yeast is still alive

Yeast is a living organism and it does die, particularly if the packet has been open in a warm cupboard. Testing takes ten minutes and saves you three hours of waiting for dough that was never going to rise.

Stir about 5 g of yeast and a pinch of sugar into 120 mL of water at roughly 40 C / 105 F. Within five to ten minutes it should foam visibly and smell distinctly yeasty. If nothing happens, it is dead — no amount of extra time will help, and the flour you would have used is worth more than the packet.

Temperature is what kills yeast

This is the single most common way home bakers lose a loaf. Liquid at about 40 C / 105 F is ideal — barely warm on the inside of your wrist. Above roughly 50 C / 120 F yeast begins to die, and water hot enough to feel properly warm to the touch is already too hot.

Cold liquid does not kill yeast, it just slows it down. If your kitchen is cool, expect rises to take considerably longer than the recipe says and judge by the size of the dough rather than the clock.

Storing yeast

An unopened packet keeps well in a cupboard until its date. Once opened, transfer it to an airtight container and keep it in the freezer — yeast survives freezing perfectly well and lasts far longer than it does at room temperature. You can use it straight from frozen.

Fresh yeast, if you come across it

Fresh or cake yeast is sold in blocks and is mostly water, so the conversion is roughly three times the weight of dried. For 7 g of instant yeast you would use about 21 g of fresh. It is crumbled into the liquid and needs refrigerating, with a shelf life measured in weeks rather than months.