Expired Milk Under the Microscope

Microscopic footage of milk before it expires, after it expires on its "best-by-date" and after being incubated to speed up microbial growth. I also tested for bacteria at each stage with a petri dish to quantify bacterial colonies.

I believe the most common bacteria after the milk was incubated  to be lactobacillus because of the following criteria: gram positive rods, growth on complex medium (milk, Tryptic soy agar), non-pathogenic since the milk was pasteurized, Indole negative, Citrate negative. This is the best guess I can make with the medium and tests available to me in my lab.

Visit the links below for more information on:

Homogenization:
https://en.wikipedia.org/wiki/Homogen...)

Pasteurization: https://en.wikipedia.org/wiki/Pasteur...

Expiration dates and how to store milk: https://www.eatbydate.com/dairy/milk/...

Curd: https://en.wikipedia.org/wiki/Curd

Whey: https://en.wikipedia.org/wiki/Whey



FAQ:


Q: The milk was pasteurized. Where did the microbes come from?


A: Pasteurization kills most but not all microbes. The ones that survived grow in the milk.



I used a Nikon D3300 DSLR camera and a Leica ATC 2000 Microscope for this video.

The Microscope magnification of each shot is shown in the bottom right hand corner.

Music is written and produced by Sci-inspi.

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