Time to ferment

Yeast is a single-cell microorganism that has been serving mankindfor millennia. Alcohol is probably the most widely recognizedby-product of fermentation, but that which is most nearand dear to our hearts is the role that yeast plays in fermentationof wheat-based dough. Working in combination withvarious bacteria, yeast, in one form or another, provides theleavening for essentially all of our leavened breads and rolls,
including pizza crusts.

The flavor, or taste, of yeast is somewhat musty, and said tobe much like that of old, wet newspaper. So why does pizza crustsometimes have such a strong yeasty flavor? Well, it’s not theyeast that you’re tasting; it’s a combination of the three mainby-products of yeast fermentation—carbon dioxide, alcohol,and acids (acetic, lactic and propionic)—that you are smelling.These are the same by-products that contribute to the wonderfulflavor of breads and pizza crusts made from a well-fermenteddough. But it doesn’t stop there; these same by-products affectthe protein of the flour by weakening it and making it more extensible,thus reducing the memory, or snap-back characteristics,of the dough, while giving the finished crust a more tender,crispy eating characteristic.

Getting Active

Because yeast is a living organism, it responds to the environmentit’s placed in, and it has a shelf life beyond which it doesnot perform well. When placed into cold water, the yeast willbe a bit slower to activate, much in the same way as cold storageconditions will slow down the activity rate of the yeast,which allows us to store our dough under refrigerated conditionsfor three or more days. On the other hand, warm conditions,especially when temperatures approach 95°F, willsignificantly accelerate the yeast activity to the point where we can get blown dough in less than 12 hours if we aren’t mindfulof temperature control.

Instantly Popular

Instant dry yeast (IDY), possibly the most widely used type ofyeast in the retail pizza industry, has a shelf life of one to twoyears at room-temperature storage conditions (65° to 80°F)when unopened. Once packages of IDY and active dry yeast(ADY) have been opened, the remaining product can be stored,tightly covered, in the refrigerator for up to one month—butremember that movement in and out of the refrigerator multipletimes could cause condensation to form on the inside ofthe package and lead to diminished performance of the yeast.The rock-hard packages of IDY and ADY (ADY can also comein a soft package) are vacuum-packaged to ensure performanceof the yeast over its long unopened shelf life. Once opened, theyeast pours freely for easy measurement. If we receive loosepackages of IDY or ADY that have traditionally been firm, wehave received a “leaker” (air has managed to leak into the package)and we should use this product as quickly as possible inorder to get maximum performance from the yeast.

The word “instant” in IDY refers to the rate of hydration,not the fermentative rate of the yeast. Because IDY is fasthydrating,it doesn’t need to be prehydrated before use; instead,the best way to add it to a dough is to simply put it righton top of the flour when you are ready to begin mixing; if youprescale your ingredients, you can mix it in right along with therest of the dry ingredients. Even when salt and/or sugar arepresent under such conditions, there is no harm to the IDY asthere would be to compressed yeast under the same conditions.If we should forget to add IDY to our dough while mixing, wecan possibly save this dough by adding the IDY dissolved in asmall amount of 70° to 75°F water. Then mix for a few minutesto ensure even distribution of the yeast, but be careful not toovermix and heat up the dough too much by mixing too long.

What’s the Difference?

All three types of yeast perform comparably and result in thesame fl avor profiles in the finished products when used at thecorrect substitution levels. As compared to 1 pound of compressedyeast, it would take 8 ounces of ADY, or 6 ounces ofIDY plus 10 ounces of additional water, to replace it. Looking atit another way, if you want to replace ADY with IDY, you woulduse IDY at 75% of the ADY amount; if you want to replace IDYwith ADY, you would use 1.33% more ADY than you did IDY.

The newest type of IDY is designed specifically to give maximumshelf life when used in commercial dry mix applications.Other “newer” types of IDY go by a variety of names, including“fast-acting,” “quick-rising,” “high-powered” and “instant premium.”Benefits of this type of yeast can possibly include betterperformance in colder dough, reduction in mix time, faster fermentation,reducedproofingtime, better ovenspring and largerfinished productvolume; and canallow for possiblereduction inthe level of IDY usage. While we may not think of these applicationsas important to us right now, at some time in the future,you may be faced with the challenge of producing your doughat a commissary for delivery to distant stores, and one of theseyeasts might be just the ticket you’re looking for to provide yourstores with the highest-quality dough, or dry mix from whichthe individual stores would produce the dough.

As you can see, yeast is a pretty unassuming, everyday product,but there’s a lot of work going on behind the scenes to makesure we get a consistent, high-quality product—in addition tonew and improved yeast types designed to meet our most challengingapplications.

Tom Lehmann is the director of bakery assistance for theAmerican Institute of Baking (AIB).

Jeff Zeak is the pilot plant manager for the AIB.Need more dough advice?Visit the Dough Information Center at PMQ.com/dough.