Instant yeast is a form of active dry yeast, just a bit more technologically advanced. Like active dry it’s grown in the fermenting tank, then centrifuged and filtered to remove much of the water. Then it’s mixed with a little oil and extruded in thin threads which are then dried, cut and packaged. The difference is that in the case of instant yeast, the mixture that’s extruded has more live cells, a result of a faster drying process that’s not as stressful on the critters. It’s also cut into very thin little oblong shapes (maybe you can see them there in the picture) that are highly porous, so they both soak up water faster and dissolve quicker than active dry granules. They also have a little ascorbic acid mixed into them, which the yeast also like.
As you probably already know instant is my go-to yeast. I love the stuff. It’s easy to find, easy to use…what’s not to love? I buy it in bulk and freeze it in a tub, then just scoop it out as I need it for the next many months. You simply add it to the dry ingredients in any recipe that calls for yeast…there’s no proving, no messing around of any kind. It’s off to the races as soon as it gets wet. It’s 15-20% more potent than active dry, but for all intents and purposes it works as a one-to-one substitute (it’s not as important to be accurate with yeast as it is to be accurate with chemical leaveners…a slightly faster rise may cost you a small amount of flavor, but that’s about it).
It’s said by some that instant yeast is so advanced it’s impervious to damage by sugar or salt when it’s in its dry state. Me I don’t believe that, so I keep it separate in the mixer bowl to be safe.