Chapter I
A Census of My Sourdough
Who actually lives in the jar?
A sourdough starter is an ecosystem in a jar: wild yeasts that make the bread rise and lactic acid bacteria that make it sour, competing and cooperating every time you feed them.
I wanted to know how many of each there were, and whether the kind of flour I fed them changed the balance.
Counting
A haemocytometer is a microscope slide with a precise grid etched into it. Drop a known volume of diluted starter on it, count the cells in a few squares, and multiply back up.
The rough census came out at about one yeast cell for every hundred bacteria, which matches what the literature says about healthy starters.
Which flour wins?
Why it’s on the shelf
The counts were noisy because I was counting by eye. Before picking this up again I want to try automated counting with image segmentation.