Credentials are in order for this discussion. I have made bread off and on for over 40 years. I have also made beer off and on for even longer. I am not a microbiologist nor do I play one on TV, for that I rely on "First Steps in Yeast Culturing" by Pierre Lajotte .
Leavened Versus Leavening
Give Us This Day Our Daily Beer
|The Sediment Is Brewer's Yeast|
|Sediment in a Bottle of Beer|
Straining At Gnats?
|Agar plate with yeast colonies|
Ancient Israel would have only known the sourdough method. They did not have the option to buy a cake of yeast after Unleavened Bread was over. They would have started fresh with flour and water to grow a bread starter. This takes a few days.
Don't Read This Paragraph
Beer makers, in their quest to distinguish their brew from the competition, get creative in choosing sources of yeast for their "wild ales". Rogue Brewing has created Beard Beer by culturing yeasts found in the master brewers beard - Mental Floss . 7 Cent Brewery in Australia used the brewmaster's navel lint as a source for yeast, "the first beer in the world fermented from yeast captured from the brewer's belly button fluff." - CNET .
Back To Leaven
|Bread leavened with wine yeast|
Back To the Future
Currently, people who keep Unleavened Bread rely on people who don't keep it. Some Jews will sell their leaven and beer and whiskey to a Gentile, then buy it back when the Days are done. Some of us keep our beer and whiskey, but throw out breads and leavening as we understand it. But still we rely on an outside source to replenish our bread supply the moment the Days are done.
Not My BEER
What to do in the meantime, till Christ comes back? Take the simplistic approach that it's not the days of unleavened beer and ignore the whole question? Or put out (as in drink up) all barley based beer because barley is one of the Five self leavening grains? Or put out beer where sediment is visible? Or search for a better answer? I guess each of us has to decide. But decide based on the Bible and facts, not just traditions.