Document Detail

Melamine and Cyanuric Acid do not interfere with Bradford and Ninhydrin assays for protein determination.
MedLine Citation:
PMID:  20228949     Owner:  NLM     Status:  Publisher    
In the fall of 2007 pet food contaminated with melamine and cyanuric acid caused kidney stones in thousands of animals. In the summer of 2008, a more serious outbreak of adulterated dairy food caused the deaths of six infants and sickened about 290,000 children in China. In all cases, melamine was likely added to inflate the apparent protein content of the foods. To determine if we could measure protein without interference from melamine and cyanuric acid we tested these compounds in the Bradford and Ninhydrin assays, two common dye-based assays for protein, as well as by ammonia release, the most common assay used in the food industry. Neither compound was detected in the Ninhydrin and Bradford assays at concentrations of >100 mug/ml. The ammonia assay detected melamine but was inconclusive with respect to cyanuric acid. To develop an accurate test for food that would not detect either chemical as a protein, assays were run on cat food and reconstituted milk powder. The Bradford assay readily measured the protein content of each food, and importantly, the addition of melamine or cyanuric acid to reconstituted milk did not affect the readings. The protein concentrations obtained for reconstituted milk powder were as expected, but those for the cat food were 10 to 30-fold lower, due to its low solubility. We conclude that dye-binding assays can be employed to detect protein in food without interference from melamine and cyanuric acid, thus reducing the incentive to use them as additives.
Anjalie Field; Jeffrey Field
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Publication Detail:
Journal Detail:
Title:  Food chemistry     Volume:  121     ISSN:  0308-8146     ISO Abbreviation:  -     Publication Date:  2010 Aug 
Date Detail:
Created Date:  2010-7-13     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7702639     Medline TA:  Food Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  912-917     Citation Subset:  -    
Department of Pharmacology, and Center of Excellence in Environmental Toxicology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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Grant Support
R01 ES015662-01A2//NIEHS NIH HHS; R25 ES016146-03//NIEHS NIH HHS

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