Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/3/2008
Publication Date: 10/1/2008
Citation: He, X., Lu, S.S., Cheng, L.W., Rasooly, R., Carter, J.M. 2008. Effect of food matrices on the biological activity of ricin. Journal of Food Protection 71(10):2053-2058. Interpretive Summary: The intentional adulteration of food with ricin as an instrument of bioterrorism is a matter of increasing concern. In order to safe guard U.S. food supply, we accessed the utility of a recently developed cell-free translation assay and optimized conditions for detecting biologically active ricin in forensic food samples. Information obtained from this study could help shape future food defense policies.
Technical Abstract: A cell-free translation (CFT) assay was applied for the quick detection of ricin in food samples. Three economically important foods, ground beef, low fat milk and liquid chicken egg were tested. The results indicated that ground beef had very little matrix effect on the assay, while low fat milk and liquid chicken egg showed clear interference on the protein translation. A simple dilution in PBS effectively eliminated the translational inhibition from these foods. The concentrations inhibiting 50% of luciferase translation (IC50) derived from the current study were 0.01 nM for pure ricin A chain, 0.02 nM for pure ricin and 0.087 nM for crude ricin in the phosphate-buffered saline (PBS). In most cases, the IC50 values for ricin in food matrices were significantly lower than those in PBS buffer, suggesting that some components in these food matrices may potentiate the activity of ricin. Thermal stability tests indicated that ricin A chain was least stable among three forms of ricin in all matrices measured. The thermal stability of pure and crude ricins varied depending on the matrices. The specific activities of ricin in PBS buffer were confirmed by neutralization test using ricin-specific and non-specific antibodies. This study demonstrates that the CFT assay is a rapid and sensitive method for detection of biologically active ricin toxin in ground beef, low fat milk and liquid chicken egg and food matrices could greatly affect the thermal stability of ricin.