Why sourdough does what it does, as short animated videos. Here are their words to
read, every fact with its source.
Sourdough Science 01
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What is a sourdough starter?
A jar of sourdough starter is alive.1 It’s a tiny town of wild yeasts and bacteria, living in flour and water.1 And bacteria usually far outnumber the yeasts, about a hundred to one.1
Feed it flour and water, and the whole town eats through it.1 The yeasts give off carbon dioxide, and that gas fills it with bubbles.1 The bacteria make some gas too, but mostly acid. That’s the sour.1, 2
Where do a starter’s yeasts and bacteria come from?
A lot from the flour. Wild yeasts and bacteria come in on the grain.3 Some may come from the baker’s hands, too.3 Others can drift in from the air, the water, even the jar.1, 3
And as you keep feeding it, more keep moving in.1 Then the sour picks who stays. The ones that can handle acid take over.1, 4 That’s why a new starter takes a week or two to settle.1, 4, 5
And why every starter is a little different, even from the same flour.3 That’s a sourdough starter: a tiny town you feed and water.
Words in the video
Wild yeasts
The starter’s main gas-makers. Yeasts do most of the work of raising the bread, by giving off carbon dioxide.1
Lactic acid bacteria
Usually most of the bacteria in a starter, making most of its acid and some gas too.1, 2, 6
Carbon dioxide (CO₂)
The gas the yeasts, and some of the bacteria, give off. It fills the starter, and later the dough, with bubbles.1
Lactic acid
Usually the main acid in a starter grown from scratch, ahead of acetic acid.1
Acid-tolerant
Able to live with the sour. As a new starter grows more acidic, the microbes that can handle it take over, and the rest lose out.1
Sources
Each fact above cites the ones it comes from. The videos show no citations; this list is
theirs too.
Calvert et al., a review of sourdough starters, PeerJ 2021Calvert MD, Madden AA, Nichols LM, Haddad NM, Lahne J, Dunn RR, McKenney EA. A review of sourdough starters: ecology, practices, and sensory quality with applications for baking and recommendations for future research. PeerJ 9:e11389, 2021.
FAO, Fermented fruits and vegetables: a global perspective, ch. 5, 1998Battcock M, Azam-Ali S. Fermented fruits and vegetables: a global perspective, chapter 5 (Bacterial fermentations). FAO Agricultural Services Bulletin 134. Food and Agriculture Organization of the United Nations, Rome, 1998.
