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I got a nylon bag which is marked 'PA' in the label, which I think is polyamide.
I plan to use it for mashing barley grains in homebrewing ( 62C to 78C, PH ~ 5, 90 minutes ).
The bag is black and was originally intended for washing clothes.
Is it food safe in this setting?
Will it leach chemicals?
Pure polyamide is foodsafe at these temperatures, they make pan spatulas out of them, which are safe to about 200 Celsius.
The problem is that we cannot know if your bag is 100% pure polyamide. It could be that the coloring is not food safe, or that it was contaminated with something inedible during production. So nobody can promise you that a nylon bag from unknown origin is food safe.
Products meant to be used in the home are unlikely to be produced where they can come in contact with extreme irritants. So you can decide to take the risk as one more potential environmental pollution, and go with it. Or you can think that it's not worth it, and look for other bags. In any case, there is no indication that the main material (nylon) will cause any trouble.
Here is a link to the U.S. Food and Drug Administrations website regarding POLYMERS. They have done a lot of testing according to the documentation provided on this page, but you will need to match specs against the table they provide, to know for sure.
Another suggestion, Submerge the bag in a very deep vessel with some purified water overnight, then test the water for changes using a water test kit, there are different brands, here is a link to a website that allow you to order one online.
The leached chemicals will not be shown in a standard test like the one you suggested. In this https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3222987/ test they used i.e. water that had been in contact with the plastics and put it on living cells to see if they got screwed up. The problem is with plastics that all of time they leach but you don't know what chemicals could be toxic, (see the study that I linked to)
