Food container "not suitable for foods with a high fat or sugar content" I'm considering getting some food containers, but I noticed most of them have this in the description:


  Not suitable for foods with a high fat or sugar content


Why is that ? What could happen if I stored some, say, chicken fat - or plain sugar - in one of those ? They're microwave and freezer safe, so how come they can't handle fat or sugar ?

In addition, are there any rules of thumb for determining which foods have a high fat or sugar content ? It's not always obvious. For example, a dish having 1/3 mince meat - would it be high on fat - and therefore unsuited for the container ?
The best reason I can come up with is that microwaving items with oil and/or fat can lead to temperatures much higher than the 90C maximum that is recommended.

From the link:


Microwave, dishwasher and freezer safe
Suitable for temperatures up to 90c
Not suitable for foods with a high fat or sugar content