In Search of Yeast!

Yeast is not a popular topic amongst guys. A small minority of guys with deep knowledge of brewing get quite excited about all things yeast, but for most it tends to conjure up awkward silences and visions of a women's health area of the drugstore that they try and avoid.

But, from what I gather so far about baking (and I have not yet been much of a gatherer), yeast is really the star of the show. For those not knowledgeable about yeast (like me prior to my wikipedia visit earlier this week), they are micro-organisms - a type of funghi - that are used in various processes that require fermentation.

In baking bread, yeast is used as a leavening agent where the fermentation process converts sugars in dough into carbon dioxide and ethanol, creating gas pockets that heat up causing the dough to rise. Baking the dough interrupts the fermentation process mid-stream. When baked, the yeast in the dough dies, the ethanol evaporates, but the air pockets remain leaving your bread soft and spongy and preventing your bread from having the flat, thick density of a hockey puck.

Sounds simple, but fermentation is quite complex from what I understand, and requires a delicate balance of yeast, yeast nutrients, enzymes, temperature, and time. If you interrupt the fermentation process too early, the dough won't rise properly and the bread won't taste as delicious because the enzymes in the dough will have had less time to break down the complex starches into simple sugars (some of the sugars become feedstock for the yeast, but much of it is left to contribute to taste and quality / colour of the crust). If you leave the dough to ferment for too long, the yeast will consume too much of the sugar and start producing undesirable by-products creating an alcohol and ammonia-like aftertaste. Lower temperatures generally slow the fermentation process, while higher temperatures tend to speed it up. Different strains of yeast are also more or less amendable to different temperatures. So, it seems the art of breadmaking depends heavily on the ability of the baker to control time and temperature in order to choose the optimal time to interrupt the primary and secondary fermentation process (or so they say -- I guess I will find out). [1]

For my first foray into breadmaking, I'll be making a sourdough boule (aka round loaf). To start with, I'll need to develop some form of sourdough starter using wild yeast. The 'sour' taste in sourdough bread is created by bacteria that feeds on lactic and acetic acids, and since the bacteria takes ~2x as long to do its work as the yeast does to leaven the dough, we need a wild strain of yeast that is a bit more resilient and can endure the long fermentation process. Good sources of wild yeast seem to be purple cabbage, organic grapes, plums, and anything else that forms that white film on the outside.

So, yesterday, I went on a quest for yeast and ended up at the Essence of Life Organic Food Store in Toronto's Kensington Market and picked up a not too sad looking ball of organic red cabbage (and organic deodorant - my wife is now powerless to my earthy scent). They also had organic grapes, but cabbage won the yeast beauty contest this time.

After arriving home, I embarked on my bread making journey by starting my starter. I'm using the recipe from Michael Ruhlman's blog (as suggested by Laura).

Sourdough starter

(from Carrie Thurman's Two Sisters and a Bakery Blog via Michael Ruhlman)

8 oz. unbleached whole wheat flour (by weight)

8 oz. water (by weight)

2 leaves of red cabbage (not by weight)

From what I gather, you basically just mix it in a bowl and let it sit overnight before feeding again. Picture of my 5-minute old starter below: [2]

Much like a pet, I will need to feed my starter with equal parts flour and water every 12 hrs or so, and the recipe suggests I should have some working starter available to start making bread in 48 hours. So the countdown begins! Will keep you posted.

Notes:

[1] Much more detailed discussion of primary fermentation in The Bread Baker's Apprentice

[2] Without going into too much detail, this is actually attempt #2. My first attempt at starter yesterday (after arriving home from my yeast quest) was not a success. I had, for whatever reason, used whole spelt flour instead of wheat flour which I understand does not generate as good a rise and has starch with different water solubility characteristics, which throws off the water/flour formula. My 'spelt' starter was looking pretty terrible this morning, so I cut my losses and re-started with some whole wheat flour this evening. Still not sure what spelt is all about. When I bought it I'm sure I thought it was some high-end super-flour since it was in the baking section of the grocery store and had some mighty nice looking packaging, but boy was I wrong. It's for people who have trouble digesting wheat. You learn something new every day.