A Melamine Field Sensor for Surety Control of Dairy Products

<p>DESCRIPTION: An inexpensive disposable sensing element that can detect melamine contamination in dairy products and serve as an on-site quality control monitor is proposed. This sensor, coupled to a battery operated reader, will serve a specific surety control needed in the marketplace after the China milk contamination of 2008. The sensor is based on Surface-Enhanced Raman Spectroscopy (SERS), which allows precise detection of chemicals that adsorb strongly to roughened SERS sensors, like melamine, into the ppb range. The SERS sensors, vapor deposited silver films with subsequent electrochemical roughening, are inexpensive to make and can be used in complex matrices like milk. As the sensors are tuned to the analytes of interest, interferences from more concentrated chemicals is limited. Therefore, an extensive separation of milk components is not required. It will be shown that a simple one-step protein denaturation is the only preprocessing required before measurement. In this program, a simple protocol suitable for on-site applications wherein a milk sample is drawn, rapidly denatured, the aqueous phase sampled and the SERS measurement made in 5 minutes or less will be presented. The SERS sensors will be read using a battery operated Raman instrument with keyed sampling chamber that ensures the SERS sensing elements are automatically aligned into the system. The compact system would be fully automated and incorporate a spectral library with partial least squares analysis. Identification and quantification of melamine would be reported to the field technician. A single reader can be used for multiple field site evaluations. The portable test would complement more sophisticated laboratory methods and would prevent tainted milk from reaching the consumer. The core concepts of this technology have been developed and demonstrated. Literature results show SERS detection of melamine and EIC Laboratories has preliminary evidence for detection of melamine in whole milk. The Phase I program is designed to define optimize and quantify 1) the SERS sensors to be utilized in this application and 2) the protein denaturing step. The latter will be optimized for melamine yield in the aqueous phase while the former will be optimized for durability, sensitivity and reproducibility. The Phase I program will demonstrate detection limits, signal linearity and precision for the detection of melamine in whole milk, 2% milk, fat-free milk and heavy cream. In the Phase I program, it will be demonstrated that variances in the milk matrix will not affect the SERS measurement precision for melamine.
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PUBLIC HEALTH RELEVANCE: Relevance: The proposed portable SERS reader with disposable sensing elements that can be used to monitor melamine contamination of milk gives the FDA and other regulatory agencies a rapid reproducible detection method to use at key manufacturing facilities without waiting for laboratory analyses. The sensors will allow larger data samplings at lower costs and can be extended to other potential contaminants.</p>