Yoghurt and raw ale under the microscope

Ken writes:

The title is intended literally, I’m afraid. I got out my microscope today and had a little play around.

Yoghurt at 400x magnification
Yoghurt at 400x magnification

I first had a look at some of the boys’ yoghurt that they’d left lying around. I diluted with a little tap water and had a look. You can’t see too much from the photo. I think the debris you can see is probably some kind of protein. When I increased the magnification to 1000x I could definitely see motile particles, which I took to be bacteria (the rest of the field wasn’t moving so that eliminates the possibility that I just had too much liquid sloshing round on the slide). The little movers were pairs and chains of little circles (cocci?). I couldn’t get a decent picture unfortunately. The photos were taken with my phone, incidentally.

raw ale, iodine stain, 400x magnification
raw ale, iodine stain, 400x magnification

This one is interesting. I stained the slide with iodine, because I want to see if there was any unconverted starch in my beer. Unconverted starch stains black in the presence of iodine. You can see form this picture that there are indeed two lumps of it. The rest of the tattered looking stuff is protein, I think. A raw ale is one that hasn’t been boiled. It’s naturally cloudy because it still has a lot of protein in it. In the bottom of the picture, the circle with a thick dark outline is a tiny air-bubble. You can’t make out any actual yeast in this photo graph, but there were a couple of yeast cells visible in the live microscope version of this picture. Unfortunately, the iodine killed off any bacteria so I couldn’t see any little swimmers like in the previous picture. I think I will try to repeat this later without the iodine.

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