Sourdough Plating Results

These are the results after 5 days of growth.

Wheat flour starter (Carl’s Friends) on top. Bottom left is the brown rice flour starter (homegrown) and the right is the immature rye flour starter.

I am a bit surprised for a few reasons. First, from looking at them I was convinced that there was no yeast growth. At first I had all three of them in a big plastic bag, and the smell was not at all yeasty. It also looked like all of the colonies on the wheat and brown rice starters were very glossy like bacterial colonies. I had previously plated both of those on malt extract agar and the yeast colonies looked very different from each other, but definitely looked like yeast. I saw nothing of the sort here. The rye starter definitely had nothing that looked like yeast, but it is still young.

The first surprise came when I opened the tops to photograph them. I first took some of the colonies from the wheat starter plate and put them in a bit of light wort. But when I took a whiff both the wheat starter plate and rice starter plate smelled very yeasty. The smell from the bag I mentioned before was from the rye starter plate. It smelled not wholly unpleasant. I could pick out acetic acid but there were other things underneath. The colonies were tiny and slightly yellow. I’m not sure if they were heterofermentative LAB that produce acetic acid or some sort of enteric bacteria.

In the end I tossed out all the plates. But now looking at the picture above I can see that the colonies aren’t equally glossy. On malt extract agar (a long time ago) the wheat starter’s yeast were flat, dull and bigger than brewer’s yeast. That kind of matches some of the colonies I see in the picture. The rice starter’s yeast looked and behaved a lot like brewer’s yeast (I planned on trying it for brewing but never got around to it. I just made some small liquid cultures.) I don’t see anything of the sort here.

Later today I’m going for a third try on the bromocresol green and dextrose plates. Hopefully I can get some distinct yeast growth since LAB aren’t supposed to grow on it.


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