Re: Does cheese contain DNA?

Hi Skippi,

Cheese should indeed contain DNA.  Where does it come from?  There are a few 
possible sources.

First, the milk used to make the cheese came from some animal, probably a cow or 
a goat.  Depending on how the milk was processed, there may be a small amount 
of DNA in the milk from the animal.  This would be from the few cells that would no 
doubt be sloughed off the animal, either from inside our outside the udders.

However, there is a more abundant source of DNA in cheese.  In most cases, 
bacteria, and sometimes fungi, are used to make cheese.  The bacteria are added 
to the milk, and over time it acidifies the milk, causing the proteins in the milk to 
clump together, or curdle.  If you’ve ever had the misfortune of seeing milk that has 
spoiled and gotten chunky, you know what I’m referring to.  Curdling can be 
demonstrated in a (slightly) more pleasant way by mixing vinegar or orange juice 
with milk.

Once the bacteria have curdled the milk, the remaining liquid is pressed out or 
allowed to drain out, and you are left with cheese.  The cheese still has the bacteria 
and fungi in it, and these organisms have their own DNA.  This is the most likely 
source of DNA in the samples you analyzed.

On a side note, you should not, under any circumstances, attempt to make cheese 
out of spoiled milk from your refrigerator!

Alex