Adulteration of food

We are currently having an issue where we are seeing plastic in our conical mill screen/grater after milling/grinding our product. This seems to indicate likely plastic inclusion into the final product. Does this mean the product is adulterated? 

Yes, foreign material is considered adulteration. But have you re-ran the post-sieve product through a sieve again to determine if plastic is indeed in the final product?

To add to above, re-sieving can help find plastic in the final product, but keep in mind that small pieces that went through the initial sieving will likely pass through again if you use the same sieve size. In a totally closed system you may miss the smaller pieces. Really the product run should be held for an investigation, some visual inspection may be required to see what kind of plastic has ended up in the final product. If this is a recurring issue you need to get to the bottom of where this plastic is coming from.

Yes---even more so because you KNOW you're finding the plastic

WIthdraw all affected batches, HOLD inventory, Shut down processing and rip the entire thing apart until you find it, replace clean and sanitize