Thursday, March 25, 2010

Mysterious Orange Reaction

I made a recipe recently which called for dried ground orange peel. Rather than buy some, we dried some orange peels and I ran 'em through the spice grinder. I ground more than we needed, and we are out of glass spice jars, so we put the ground peel in a disposable plastic container (like the ones that come with salad dressing at some restaurants). The following day, Stacy noticed that the container melted:
The bottom of the cup actually "melted;" it got stuck to the top of the spice rack.  It wasn't due to heat, I don't think. The plastic kind of went mushy and soft; the bits melted on to the top of the rack could be wiped off!

Here's a shot of the bottom of the thing after we peeled it off:

It was so soft, you could mush in the sides:
I honestly have no idea what caused this, but if anyone has ideas, I'd love to hear 'em!


  1. Perhaps some of the citric acid that oranges have is in the peel.

  2. The container is probably Low density polyethylene (#4), which is supposed to withstand acid.

    However, it isn't very resistant against aromatic solvents. One of the components of orange peel is orange oil, and I suspect that the container might slowly dissolve in it. Limonene is sold as a cleanser, so I think the best bet is to obtain some and see if anything happens.

  3. If you want to do a fun experiment with an orange peel I can be of some assistance. Take a small piece of peel and a lighter (fire!) and hold the flame next to the outside of the peel then squeeze the peel so that the oil squirts out. Fun ensues, just don,t burn yourself and if you are plastic make sure you don't melt.

  4. Orange peel also makes a great Cartesian diver. No more fiddling around with clay and pen caps!

  5. I sense lots of orange peel fun coming up very soon,

  6. So, between comments here and on Buzz and Facebook (aren't I the social networking butterfly!) 3 people suggested the citric acid. The thing is, I don't think there's that much of the stuff left in the peel. Also, I've stored salad dressing containing vinegar or lemon juice in these containers without any trouble.

    notElon is right about the oil content, but not the plastic. The thing is, the cups (SOLO B200) are made of polystyrene, not LDPE (see pg. 129). Not sure where this leaves us. Does limolene dissolve this plastic? Any ideas where to find some of that stuff to try it out?

    Aryeh - I've tried that in the past without any success. Have you gotten it to work? If so, I want to see (Pesach science, anyone?).

    notElon, how do you use orange peel as a Cartesian diver?

  7. Yeah, Polystyrene is the other material I thought they might be made from. Generally it has a reputation for being stronger, but maybe it dissolves too.

    Limonene can be found here and here. I couldn't help but notice it says "May be harmful to plastic," so that seems like a good sign.

    There also seems some anecdotal support for it.

  8. Lemons, oranges and other citrus contains acids, one of them is the citric acid. The acid is so strong that it can cook a fish when you soak it with its juice. No wonder that plastic melted.

    Anyway, it is not dangerous for us to intake this ground orange peel but not too much.

    To avoid that incident from happening, it would be better if you place it in your spice rack, where your spices and herbs are placed.

  9. This has happened to my measuring cup while making an orange cake. Definitely not sub standard plastic here. Most bizzare- doesn't seem to happen with lemon zest