Supermarket plastic bags are made of high density polyethylene, and I am interested in the decomposition products at high temperature: what type of compounds are released and how dangerous are they? I am interested in a situation where one has placed some kind of heated food inside one of these plastic bags.

The question is, are harmful compounds from the plastic bag passed into the food (food is hot, like baked bread) contained inside the plastic bag?

  • $\begingroup$ PE does not decompose at 100°C unless perhaps if kept at such temperature for an extended time period. $\endgroup$ – Karl Apr 3 '16 at 20:48
  • $\begingroup$ the bag is not "decomposed" i updated question. just hot food inside a plastic bag. $\endgroup$ – Dror Apr 3 '16 at 20:59

Polyethylene is generally considered suitable for food handling and even for warming food. Unlike some plastics such as polycarbonate, it does not need an additional plasticizer that could be toxic.

That said, the melting point of polyethylene is ~1150C, and I've found that it tends to shrink-wrap around microwaved food. For that reason, polypropylene, m.p. ~1300C, is often used for food containers intended for microwave oven use and for automatic dish-washing.

BTW, both polyethylene and polypropylene absorb some of the natural lycopene coloring of tomatoes or other carotenoid pigments and slowly develop a pale brown discoloration that cannot be removed, but that is of no significance.

  • $\begingroup$ Thank you DrMoishe for your answer. The question lays on what does "generally considered" means. Any real test on that subject? $\endgroup$ – Dror Apr 4 '16 at 4:59
  • $\begingroup$ As you wouldn't know what effect to look for, it is hard to make a real test. Ordinary PE does not contain anything that is low molecular weight and could mirate, and it doesn't produce anything in that direction if not heated too far above 100°C for too long. $\endgroup$ – Karl Apr 4 '16 at 14:34
  • $\begingroup$ What you are saying is that HDPE plastic bags shouldn't pass any compounds to the heated food (talking only below 100°C) when touching each other..? $\endgroup$ – Dror Apr 4 '16 at 14:47
  • $\begingroup$ Just the label ink, if used inside-out. There should be no health hazard, but a melted PE bag is a nuisance to remove. $\endgroup$ – DrMoishe Pippik Apr 4 '16 at 20:31

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