Saturday, March 17, 2007

PV = nRT

Is any random reader of my blog a chemist and can explain this phenomenon? The last time I made it out to my condo to pick up mail, I noticed the bottle of olive oil I had bought from The Milk Pail Market had squished like a shampoo bottle after being on an airplane. No one had been living there and the bottle hadn't been opened for half a year. I loosened the cap and indeed air sucked in and the bottle popped back into shape.

I thought, well, the air pressure outside hasn't changed, and the temperature hasn't fallen that much, so it seems that some chemical reaction is sucking some of the gas molecules. You normally don't notice this because olive oil or cooking oil isn't normally stored in flimsy plastic bottles left alone for half a year. What's the chemical equation for oil going rancid? Yeah, so this is what I think about during my twenty minutes of functional time per day.

By the way, The Milk Pail has very good olive oil. And very good asparagus, especially asparagus tips, in asparagus season, which is coming up in April. I can't comment on much else since I only went there a few times, but it's very convenient to do your shopping there right before DL rehearsal. It's a good place to get inexpensive gourmet produce and cheese.


Lara said...

i know nothing about chemistry. sorry. :-P i could write a poem about it, though... maybe.

dancing dragon said...

Hehe, my friend actually did once write a poem based on my biology lab report on fruit flies. :D

Mazurka said...

Hi, DD. I got pointed at your site by a friend who thought I might know the answer.
The really short answer is 'lipid oxidation'. Basically, the triglycerides are breaking down, sucking in some oxygen, and forming peroxides. It means the olive oil is going rancid.
There are a couple of mechanisms for the oxidation. In your case it was probably photo-oxydation or enzymatic peroxidation. Keeping the oil out of the light may help it keep longer. I don't know about six months, though.
Check out here and here for more info.

dancing dragon said...

Wow, thanks! I really wasn't expecting anyone to answer that!