Evaluation of a commercial lateral flow feed test for rapid detection of beef and sheep content in raw and cooked meats

Abstract

Meat species adulteration is a common problem in the retail market. This study investigated the feasibility of a commercial lateral flow immunoassay designed to detect ruminant muscle tissue in feedstuffs, such as “meat-and-bone meal” (MBM) for detection of beef and/or sheep flesh in meat mixtures, and developed a simple method for meat sample extraction. Laboratory adulterated samples including raw, cooked (100 °C, 30 min), and sterilized (121 °C, 15 min) beef-in-chicken, beef-in-turkey, and lamb-in-pork at 0 to 1.00% (w/w) adulteration levels were extracted by different solvents (tap water, NaCl, and PB–NaCl with and without EDTA; and a kit-provided “Extraction Solvent”) using three mixing methods. The test rapidly (20 min) detected 0.50% (w/w) bovine or ovine meat; Extraction Solvent was the most efficient extractant tested; EDTA coupled with heating (100 °C, 10 min) improved the assay sensitivity; and all the mixing methods achieved the same results. This immunoassay can be conveniently applied to detect low levels of beef/sheep meat in a wide range of meat products.

Introduction

It is imperative that meat products sold for human consumption must be accurately labeled as to the species they contain. Species adulteration is not only a concern in imported products, but also occurs in restaurants and at the retail level where the substitution is easy to conceal. Fraudulent adulteration or unintentional contamination of undeclared meat species has been reported in many countries (Barai, Nayak, Singhal, & Kulkarni, 1992). In the United States (US), species adulteration has been found in both fresh and cooked meat products, with a higher violation rate (22.5%) in cooked meats than in fresh ground meats (15.9%) (Hsieh, Woodward, & Ho, 1995). Another study (Hsieh, Wetzstein, & Green, 1996) reported that 90% of market-made ground pork sausage samples contained undeclared beef and/or poultry, while 54% of the pork sausage samples contained other meat species. Among these adulterated sausage samples, 62% were contaminated with a single species, 36% with two species, and 2% with three species (Hsieh et al., 1996). In Australia, a survey reported that 11% of cooked meat samples and 13% of raw meat samples were inaccurately labeled (Western Australian Food Monitoring Program, 1999). In the United Kingdom (UK), 14.6% of retail meat samples tested were identified as having labels that did not declare a species of meat detected within them (Ministry of Agriculture Fisheries & Food, 1999).

Meat species adulteration not only constitutes economic fraud, thereby betraying consumers’ trust in the meat industry, but is also a concern for those with religious taboos, moral aversions, or allergies to particular meat species. For example, in one study beef allergy was diagnosed in 11 (3.28%) out of 335 atopic children (Werfel, Cooke, & Sampson, 1997) and the incidence of beef allergy may be as high as 0.3% in the general population (Fiocchi, Restani, & Riva, 2000). In addition, once a meat product has been adulterated by an unknown meat, the ability to trace the sources of possible species-associated pathogen contamination is lost. This could be a serious issue for food safety if the adulterated meat is not cooked to the required minimum internal temperature to destroy contaminating pathogens (Levine, Rose, Green, Ransom, & Hill, 2001).

Several methods, such as electrophoresis, chromatography and DNA-based assays, are currently available for meat species identification (Hsieh, 2005). However, none of these methods is rapid and economical, and all require highly trained inspectors. Recently, a single-step lateral flow immunochromatographic ruminant assay (Reveal for Ruminant in MBM) became commercially available. This test kit is specifically designed to detect prohibited ruminant bovine and ovine proteins in animal by-product, meat-and-bone-meals (MBMs), for the surveillance of bovine spongiform encephalopathy (BSE) epidemics. In a validation study (Klein, Lupo, Pielack, & Mozola, 2005), this test was found to be specific to ruminant muscle protein without any cross-reactivity with many feed ingredients, such as lecithin, vegetable oil, whey, animal fat, brewers yeast, molasses, porcine and bovine plasma, etc. and capable of detecting as little as 1% ruminant tissue in animal feed products. In another evaluation study (Myers, Yancy, Farrell, Washington, & Frobish, 2005), this test demonstrated 100% selectivity (0% false-positive results) with a detection limit of 2% bovine MBM in dairy feed. Due to concerns that have been expressed regarding the prevention of BSE and the potentially life-threatening hazards associated with beef allergies in many consumers, we attempted to explore the feasibility of this feed assay for detecting the presence of beef and/or sheep meat in raw and heat-processed meat products for human consumption. The specific objectives of this study were to optimize the assay conditions for meat testing, and to determine the assay’s detection limit for beef and/or sheep flesh in raw, cooked and sterilized non-ruminant meat samples.