[Shannon Chastain]

Shannon Chastain  asked the Naked Scientists:
   
Hi!

These days I am a full time stay-at-home mommy and home school my kids.  We studied physics last year and are studying chemistry this year on a 1st and 2nd grade level.  While I wouldn't trade my job for anything, I do miss the world of research science quite a bit.  (I have a degree in molecular biology.)

So, needless to say, newbielink:http://www.thenakedscientists.com/HTML/podcasts/ [nonactive] and was so excited to find it as a newbielink:http://www.thenakedscientists.com/HTML/podcasts/ [nonactive]!  Thank you for all the hard work all of you put into it!

I have a question for you...

This past summer we moved back to the United States from the Netherlands and really miss some of the food that we were able to buy at the markets.  One of our daily staples was quark.  I recently found a recipe for making it, and the first time it worked beautifully!

2 cups buttermilk
1 gallon of milk

--let this sit at room temp for two days. 
--then heat the mixture it in a crock pot or oven on low temp and the curds separate from the whey.
--I creamed the curds in my food processor (the texture was like thick yogurt) and we had a wonderful taste of the Netherlands for breakfast!

The second time, I decided to make a larger batch and covered my bowl with aluminum foil.  Since the bowl was so full, the foil touched the surface of the buttermilk/milk mixture for the first 24 hours, until I noticed that something (the bacteria? or was it too acidic?) was eating away at the foil.  There were several little holes in it, and I could already notice a marked difference in the surface texture.  It kind of looked and felt like a white sponge had taken over the surface, and the whey had already started to separate from the curds.  By the end of the second day, I wasn't sure it was going to turn out, but I decided to heat it anyway.  When I tried to "cream" the resulting curds in my food processor, they were very grainy.  The end result was almost like the texture of ricotta but with even more of a grit to them.  Needless to say I threw it out!

What happened?  I won't be using foil again!

Thanks,

Shannon Chastain
Princeton, NJ

What do you think?

[RD]

The second time, I decided to make a larger batch and covered my bowl with aluminum foil.  Since the bowl was so full, the foil touched the surface of the buttermilk/milk mixture for the first 24 hours, until I noticed that something (the bacteria? or was it too acidic?) was eating away at the foil. 

The bacteria in milk produce acid ... http://en.wikipedia.org/wiki/Lactobacillus

Acid can dissolve aluminium foil.