Dear Charles C.,
A very good point of view, indeed. Well, the choosen of 7 mm as a minimum dimension is somehow ridiculous to other people. But, the further question is, how did you prevent the 5 mm objects for being contaminate your foods? If it was a metal substance, the metal catcher was possibly able to accomplished that task (some metal catcher do not able to catch that size of metal). But what about the non-metal substance?
IMO, the sieving is the most possible way. But the problem is, how is the characteristic of our products? For example, my products is a powder form that well passed through 20 mesh (about 0.85 mm aperture). As blink of an eye, it safe for the 7 mm dimension. But a wire with 10 mm length, but with diameter size 0.5 mm, can easily through the siever! That wire only can be detained by 60 mesh siever size. But if I am using 60 mesh size, most of my products will be detained too.
So IMO, if we will use sieving as a preventive purpose, we should look at the characteristics of our products and the threatening foreign material. Frankly speaking, I cannot use a tighter regulation than the FDA, because the consecuence is I will loose most of my products. But I still need to convince my auditor (by hypnotism or voodoo?), that our threatening foreign material is not a kind like wire that I've mentioned on the above. From the historical data, we only found plastics, wood, rubber, that can be detained on 20 mesh siever.
Regards,
Arya