What is that white stuff inside my Ziploc Brand Container?

July 16, 2012 8:09 PM

What is that white stuff inside my Ziploc Brand Container?

It happens not only to my Ziploc Brand Containers but also (to a lesser degree, I think) my Tupperwares. I buy new containers, use them for a while - about a year, moderate use - and I start seeing very small, white crusty stuff forming inside the containers. At first sight it looks like dried food bits, and sometimes tiny white bubbles. But when I scratch it, white bits fall off and leave a mark and very slight dent on the wall of the container.
I don't use a dishwasher, but I do use very hot water when I hand-wash my containers. I usually try not to microwave plastic containers, and use them mostly for storing cold food.
I googled and searched but couldn't find any satisfactory answer - I was surprised no one else seemed to be experiencing this. I checked Ziploc website, but they only recommended replacing a container if the lid doesn't fit or if the container cracks - and neither has happened to any of my containers.
I guess I am ultimately wondering if these containers are safe to use for my cold and hot food, or if this means I need to get new containers..

posted by eisenl to food & drink (9 answers total)

Probably the plastic of the container that starts to abrade and fluff up a bit from wear. A minor, IMO, concern could be those spots harboring bacteria. Another concern could be ingesting small amounts of food-safe plastic. I personally don't worry about those things and have continued to use plastic containers in similar condition.
posted by 6550 at 8:16 PM on July 16, 2012

I think if this is happening after a year of moderate use, you should replace these cheap containers. Maybe upgrade to glass.
posted by mattbucher at 8:18 PM on July 16, 2012 [3 favorites]

I get that too. I decided it was from stacking them inside each other. I think the plastic abrades. Mine were relatively expensive so I'm going to keep using them!!
posted by bquarters at 8:41 PM on July 16, 2012 [1 favorite]

Might have been seeing it more in knockoff brands, myself but it has happened to both Tupperware and Ziplock brand stuff, too.

I suspect that during microwaving, if oil can melt and accrue in local spots, the heat imparted to it from the water that gets heated from the microwave gets it hot and long enough to melt local areas especially around gaseous nucleation points (or cause to expand gas bubbles int he plastic just under the surface of the material).

"Good" kitchen plasticware has a recycling code 5, which is polypropylene. Some fringe yammering, but this is one of the better plastics for storing biological materials. Very stable, very resilient, quite inert, and has good resistance to corrosives.

I've been trying to replace a percentage of my plasticware with glass as my budget allows but glass is a lot heavier, bulkier, and much less stackable. I have no qualms using quality plasticware and the blemish is not more a health issue than unblemished plasticware.
posted by porpoise at 8:55 PM on July 16, 2012 [1 favorite]

Whoops, sorry, reading comprehension failed. So bits flaking off without microwaving; check to see what the plastic recycling code is and make sure it's 5 and not counterfeit.
posted by porpoise at 9:04 PM on July 16, 2012

It's probably the very hot water you're using to wash them. I had the exact same problem with Ziploc twist and lock containers and noticed that it happened after microwaving and after washing them in the dishwasher. Also, the ones I used for storing tomato sauce seemed to deteriorate faster - the white gunk would accumulate right at the "sauce line" in the container. I experienced this after using them for awhile, too - probably about a year.

I stopped using them and now prefer glass. Ultimately, the Ziploc containers are disposable, so getting a year of use from them is probably more than they are built for - that's what I told myself when I finally recycled them, anyhow. I like to use things until they fall apart and the white gunk didn't obviously fit that category for me, but I made peace with that for the most part.
posted by k8lin at 12:22 AM on July 17, 2012

I've seen that too. What it looks like to me is that the plastic starts to delaminate, and the different layers start to oxidize. Or get food residue in them.
posted by gjc at 5:19 AM on July 17, 2012

As others have pointed out, glass is the way to go.

That stuff is flakes of plastic, it got scratched, or burned, or abraided in some way and now it's flaking off.

Some believe that re-heating foods in plastic or storing food in plastic will leach cancer-causing initials into your food.

You don't want that.

Buy some pyrex, you'll be happy.
posted by Ruthless Bunny at 6:00 AM on July 17, 2012

Glass breaks.

I have seen this. The interface where content meets dish surface and air.

I do not see this sort of problem in plastic dishes primary used, for example, to take stuff to work for lunch. Instead it's in dishes used for acidic tomato sauce or even chicken soup (!). The fact the soup does it is what makes me think the edge of the air plays a role.
posted by Goofyy at 12:14 PM on July 17, 2012