Those were fragments of razor blades embedded in the fish cakes.
As for the fingers, they belong to the unfortunate worker who came to see us after taking the first two bites and realized there was this metallic thing from the other end of his bite.
There were several other shots taken of the multiple iron enriched fishcakes but I think these would suffice. Probably an unhappy worker decided to come up with something foolish to prove his point. ( or was there a point in the first place .. )