“I understand the big food companies are developing a tearless onion. I think they can do it–after all, they’ve already given us tasteless bread.” –Robert Orben
(quoted on http://www.twobluebooks.com/ – where you can buy Bread Science: the Chemistry and Craft of Making Bread. Emily Buehler)
This site has a number of excellent resources. It also directs you to the following blog reviewing the above book: http://www.wildyeastblog.com/2009/05/10/bread-science-giveaway/
as well as an article touching on the same topic: http://www.newsobserver.com/2011/01/31/957315/the-secret-life-of-yeast-bread.html which offers the following explanations:
After mixing in more flour, water, yeast and salt, she transfers the sticky mass to the countertop and begins to knead: pressing the heels of her hands into the dough, folding it over, and pressing again with a rocking motion.
Invisible to the eye, an elastic network begins to form within the dough. Protein molecules in the flour called glutenin and gliadin link up during kneading to create a larger complex called gluten, Buehler explained.
Gluten is what makes bread chewy. Think bagels, or pizza crust.
During the kneading process the coiled, kinky gluten molecules cross-link into a stretchy 3-D latticework, Buehler said.
As she continues to knead, the dough is transformed from a sticky, shaggy mess into a smooth, satiny ball that is delightfully malleable; when fully kneaded and pinched between the fingers it has the consistency of ear lobes.
Buehler transfers the dough to a bowl and covers it with a towel. An hour later, the dough has doubled in size.
The powerhouses behind this transformation, she explained, are tiny microorganisms – single-celled fungi called yeasts. Too small to see with the naked eye, yeasts take in oxygen and expel carbon dioxide, just as we do when we breathe.
Enzymes in the flour break down starches into simpler sugars, which yeast and bacteria eat, Buehler said.
Given enough food, time, and a comfortable temperature, the yeasts grow and multiply, producing gas and alcohol as a byproduct through theprocess of fermentation.
“Bread is essentially yeast burps and sweat,” said Peter Reinhart, baking instructor and faculty member at Johnson & Wales University in Charlotte.
The same basic process is what makes champagne bubbly and beer foamy. Although there are hundreds of different yeasts, we use the same species, Saccharomyces cerevisiae, for both baking and brewing.
“Beer is basically liquid bread; they were invented around the same time,” Reinhart said.
On the wild side
Long before we could buy yeast in the grocery store, people made bread by letting mixtures of flour and water spoil naturally.
Wild yeasts in the air and on the surface of grains make themselves at home in the flour-water mixture, producing lactic and acetic acids that give breads such as sourdough their distinctive tangy taste.
“When we use baking powder or baking soda, we’re mixing alkaline and acid to make carbon dioxide, but in a chemical way rather than a biological way,” he said.
But in yeast breads, as the dough ferments, it fills with gas and inflates from within. Millions of tiny bubbles get trapped in the gluten and expand, creating the characteristic air holes in a slice of bread.
“Some people think of it like tiny balloons,” Buehler said.
Gluten gives dough its strength and stretchability, but is also a source of gastrointestinal distress for people with celiac disease or other gluten insensitivities, Reinhart said.
Reinhart, author of “Whole Grain Breads” (Ten Speed Press, 2007) and five other books on bread-making, is now hard at work on a gluten-free baking book.
The challenge for gluten-free bakers, he explained, is to mimic the spongy texture of bread without using wheat flour.”