A validated Trichinella digestion assay and an associated sampling and quality assurance system for use in testing pork and horse meat

Abstract

A revised digestion method, developed for efficiency and quality assurance, was validated for the detection of Trichinella larvae in pork and horse meat to meet requirements for food safety testing and facilitate access to international markets. The method consisted of a tissue homogenization step and a spin bar digestion procedure conducted at 45 degrees C to free larvae from muscle tissue, followed by two sequential separatory funnel steps to concentrate the larvae for detection using a stereomicroscope. Critical control points were determined for the method and monitored during testing. Under conditions of a defined protocol, test capacity was suitable for industrial applications, since multiples of up to 100 g of tissue could be analyzed at one time. The overall sensitivity of the test system depended on the size and origin of the sample taken from individual infected carcasses. Data from swine indicated that the currently accepted sample size of 1 g from individual carcasses consistently detected larval loads of > or =3 larvae per gram. Larval loads of 1.0 to 1.9 larvae per gram required 3- to 5-g samples of muscle tissue for reliable detection. Five-gram samples were considered optimal, because they consistently detected more tissues than 3-g samples, although the difference was not statistically significant. Tissue localization studies in experimental pigs indicated that the tongue and diaphragm were the tissues of choice for the most sensitive larval recovery. A system of analyst training, laboratory certification based on ISO guide 25, and on-site proficiency panel testing was used to ensure that external laboratories would consistently produce reliable test results. The system developed for pork was successfully modified for the testing of horse meat.