I know that instant dry yeast immediately goes to work on the dough, but is there any difference in the final dough made with instant dry yeast versus active dry yeast? Texture, flavor, oven spring, etc?
What kind of yeast is preferred for making the best pizza dough?
Several years ago, Tom Lehmann and the American Institute of Baking conducted tests in which they used fresh yeast, active dry yeast (ADY) and instant dry yeast (IDY) to make pizza dough. When they examined the finished crusts, they could not tell which crust used which form of yeast. However, that is not to say that there aren't differences between the three forms of yeast that can have specific effects on the finished dough. But the explanations of the differences become very technical, with distinctions between lean and sweet doughs, gassing power, etc., as you will see if you read the Yeast Treatise at the theartisan.net website at http://www.theartisan.net/yeast_treatise_frameset.htm
and the BakingBusiness article on yeast at http://www.pizzamaking.com/forum/index.php/topic,8912.msg77255/topicseen.html#msg77255
You will get different opinions on the relative merits of the three forms of yeast in a home environment. Most members tend to use the dry forms of yeast because they have long shelf lives, whereas fresh yeast has to be used very quickly and has a very short shelf life (it is also much harder to find in supermarkets than ADY and IDY). The members are pretty much split as between ADY and IDY. Some prefer IDY over ADY because there is no need to rehydrate IDY. IDY is also considered better for frozen doughs. Most problems with ADY tend to stem from using the wrong water temperature to rehydrate the ADY. One member prefers ADY over IDY because it has more dead cells than IDY, as noted at Reply 18 at http://www.pizzamaking.com/forum/index.php/topic,3985.msg34030.html#msg34030
All three forms of yeast can, by themselves, contribute to the final crust flavor, in the form of a "yeasty" taste. However, according to Professor Calvel, in his book The Taste of Bread
, you have to get above about 2.5% of the weight of the formula flour for fresh yeast to taste it in the finished bread. I have not seen the corresponding numbers for ADY and IDY but I would guess that you would perhaps have to get somewhere in the range of 1-2%, and possibly even higher, to be able to taste them in the finished product.
For a mini-tutorial on yeast, you might take a look at Tom Lehmann's post at the PMQ Think Tank at http://thinktank.pmq.com/viewtopic.php?p=50956#50956
. However, I would ignore the storage advice. I freeze my dry yeasts and they last for years.