The accurate labeling of meat products is mandated and monitored by the United States Department of Agriculture (USDA) as well as by state and local governments. Mixing undeclared species in meat products is illegal under Food Labeling Regulations. Apart from regulatory reasons, the prevention of adulteration of meat products with less desirable meat species is important to the consumers for economic, health, food safety and religious reasons.
Several methods have been developed to identify meat species including electrophoresis, chromatography, DNA hybridization, and immunoassays. Immunological techniques, including agar-gel immunodiffusion (AGID) and enzyme-linked immunosorbent assay (ELISA) are most commonly applied for meat species identification.
There are several disadvantages to the official method AGID. Concentrated antiserum preparations are required to obtain visible precipitin lines in AGID. Obtaining the antiserum is expensive in large-scale testing. Furthermore, the sensitivity of AGID is variable. Usually ten percent or more contamination must be present to detect adulteration with this method. Lastly, AGID cannot be used for species identification in cooked meat because of the shortage of commercial antiserum specific to cooked meats.
The ELISA method has emerged as a sensitive, rapid, and specific method for meat speciation. This method can detect levels as low as one percent or less of meat contamination. Furthermore, it requires only simple sample preparation and no expensive equipment or highly skilled operator. In addition, the ELISA technique can be used for both qualitative and quantitative analysis of meat proteins.
Specific antibodies, either polyclonal antibodies or monoclonal antibodies (MAbs), are required as capture reagents in ELISA. Most of the ELISA methods currently employed for meat species identification use polyclonal antibodies as a capture reagent. However, polyclonal antibodies have disadvantages such as limited production, variable affinity and a requirement for further purification to eliminate cross-reaction.
Using monoclonal antibody based ELISA can provide better data quality and eventually reduce the cost of assays. To date, the monoclonal antibodies which are utilized in ELISA based assays for meat identification have been raised against native proteins. The antibodies are useful for the detection of meat in raw meat mixtures.
A few disclosures of the production of polyclonal antibodies for the qualitative detection of meat species in cooked meat samples has been reported. These polyclonal antibodies have been raised against native heat-resistant immunizing antigens.
Wide spread meat species adulteration has been found particularly among heat-processed meat products and retail meat markets. Hsieh et al. (1995) Jrnl. of Food Quality 19:1-13, indicated that the violation rate in cooked products was higher than raw meats (22.9% versus 15.9%) in the domestic market. This adulteration can have serious health consequences. Poultry carries pathogens that cause food-borne diseases. Cooking poultry requires a minimum internal temperature of 71.1.degree. C. (160.degree. F.) to kill salmonella. Beef requires a minimum internal temperature of 68.3.degree. C. (155.degree. F.) to kill E. Coli H7:0157. If a meat product like beef is contaminated with poultry meat, it might impose a potential health hazard due to the inadequate heat-processing even at a very low level of contamination.
Development of a suitable screening method to detect undeclared exogenous meat is important to comply with the food labeling regulation. Furthermore, a means for determining the adequate end-point cooking temperature for food safety is also important.
There is, therefore, needed a method for the determination of species identification in cooked meats as well as to determine the end-point cooking temperature of meats.