New Tools to Help Detect Melamine in Skim Milk Powder

A newly proposed standard and associated supportive reference materials for authentication of skim milk powder were posted December 31 by the U.S. Pharmacopeial Convention (USP) for public review and comment. Development of the proposed tools, aimed at preventing economic adulteration of skim milk powder with melamine and other nitrogen-rich materials, was prompted by the reports of melamine contamination of milk products in China, according to a USP official.

“The melamine scandal highlighted one of the weaknesses of our dairy supply chain: How we measure protein,” says Markus Lipp, PhD, USP’s senior director of food standards. “By and large all current protein determination methods are susceptible to the presence of melamine, in that melamine shows up as if it were protein. Our challenge was to strengthen existing tests for protein, so that they are not as readily fooled by the presence of chemicals such as melamine.”

The proposed standard, “Non-Protein Nitrogen Determination for Skim Milk Powder,” is supported by two reference standards: USP Skim Milk Powder and USP Skim Milk Powder with Melamine Level D. This is the first time USP has produced a deliberately contaminated reference standard for a food ingredient, Dr. Lipp notes.

“We did our best to mimic the conditions in which melamine adulteration is thought to have happened in real life,” he says.

The new tests will not detect the presence of melamine, but rather will “allow the analyst to see that something other than protein is present in the sample, something that may mimic protein under certain test conditions but not other test conditions.” This then serves as a warning of potential contamination or adulteration.

The proposed standard is posted in the most recent Food Chemicals Codex Forum and open for comment until March 31. Also posted are the first proposed USP monograph for a probiotic type of food culture and a proposed modernization of existing chromium picolinate and chromic chloride monographs.

The probiotic ingredient, Bacillus coagulans GBI-30, 6086, was the first bacillus to receive a designation of generally recognized as safe from the FDA in 2012.

The proposed monograph is specific to the strain level and applies only to food ingredients that are labeled as this specific strain of Bacillus coagulans, according to USP.

“Probiotic standards need to be very specific, for the specific strain of the bacteria,” Dr. Lipp says. “That is how the regulations are written, and that’s how all the efficacy studies work.”


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