Curdled Milk (Bio60_2018)

I stumbled across this picture somewhat by accident. Four days ago, I collected a sample from my glass of milk at breakfast, intending to examine it that same day. Much to my dismay, looking at it through my Foldscope, I saw nothing at all! In hindsight, I should have expected this – the milk was pasteurized, after all. After my initial disappointment, I set the sample aside, and promptly forgot about it. Flash forward to today, and you’ll find me realizing in shock that I had forgotten to make this post. I whipped out my Foldscope, and lo and behold, that sample of (now spoiled) milk was still there, but it now looked so different. I could see that it had curdled, and there was a solid white deposit mixed in with the rest of the liquid milk. This time, when I dropped the cover slip over a drop of the milk, I could see a much more opaque white stain where the milk was, and it looked like it had little rivulets running through it. Placing my eye to the Foldscope, I saw an entirely different world than the one I had seen 4 days prior. There was an almost crystalline feel to the milk stain, and it was a yellowish-white color. I could see little flakes moving around the spaces as I tilted the Foldscope back and forth as well. I was definitely surprised by what the milk looked like – I had expected to see something like little globules of milk fat, or perhaps to see some bacteria, but instead the milk was more hardened and flaky. But perhaps it was a good thing that there were no bacteria to see, considering that the sample came from my breakfast! Moving forward, I would love to see what different types of milk look like – i.e. Nonfat milk, 1% milk, whole milk, chocolate milk; I would also be interested to see how the sample changes over time, perhaps waiting up to 2 weeks (yikes!).

This specimen was pipetted from a glass of milk 4 days previously, and allowed to curdle in a small test tube. Note the flaky, crystalline structure.

One Comment Add yours

  1. Manu Prakash says:

    What a beautiful journey to discovery – I am so thrilled you shared the set of events as they happened. So often, we read about end results but not the stories of discovery. This is a fantastic one.

    Also; We should not rule out that bacteria might be at play here. Our air is filled with bacterial spores – and milk is a fantastic “medium” – not all bacteria swim – and many will form a biofilm that would look exactly like you share a picture of.

    I would love for you to do more controlled experiment; maybe let milk go bad with and without cover from air?

    Also; here is a mother’s breast milk as a comparison – another fantastic post..

    Keep exploring..


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