The melamine addition may be a fairly common thing in China, where the contaminated stuff came from. Some recent articles appear to say that the market for human food is rife with "unapproved adulterants" there. Several non-food approved dyes/colorants have been cited along with the apparently common melamine (fertilizer) additions. Fairly common use of agricultural and industrial chemicals rather than "food grade" materials is claimed, although the reports I've seen lack really credible citations.

A latest in the "pet food" recall cycle appears to be an investigation of melamine spiked agricultural (esp. hog) food, and at least one US hog herd supposedly has been blocked from being slaughtered for market because of alleged confirmation that they were fed melamine doped food. (Note: lots of weasel-words should indicate the quality of reports I've seen.)

I haven't seen details, but some reports imply that the addition of melamine does not actually affect (raise) the protein content, but only makes it appear to have a higher protein content than it actually does when it's tested by ordinary methods. Has anyone seen a clarification on this?

John