THE EFFECT OF COOKING ON VETERINARY DRUG RESIDUES IN FOOD .2. LEVAMISOLE

The heat stability of levamisole was investigated. Results obtained in dicated that the drug was stable in boiling water at 100 degrees C, bu t unstable at 260 degrees C in cooking oil, with a half-life of about 5 minutes. The effect of cooking (microwaving, boiling, roasting, gril ling and frying) on levamisole residues in a range of fortified and in curred tissue was studied. No evidence of instability was obtained in any of the cooking methods investigated. Most observed net changes fel l within the limits of the precision of the method once allowance for weight loss during cooking was made to counter an apparent increase in concentration. Roasting was the only method of cooking where a net lo ss of levamisole was observed. Insufficient juices were produced to pe rmit analysis in this instance. The net loss of levamisole in the cook ed tissue was similar to that found with other cooking methods, where the levamisole lost was found in the cooking liquid or juices. An asse ssment of homogeneity of the incurred tissue used in the investigation was made. The pig muscle was found not to be homogeneous with larger differences seen between different areas of the animal than within the same muscle. The findings of this investigation showed that data obta ined from measurements on raw tissue are suitable for use in consumer exposure estimates and dietary intake calculations.