Ractopamina em carne suína: validação de método por ensaio de imunoadsorção enzimática e estudo de ocorrência

Abstract

Pork is the most widely produced and consumed meat in the world and Brazil is the fifth largest producer and fourth largest exporter of this product. Ractopamine (RCT) is a beta-adrenergic agonist and is allowed as a growth promoter in several countries, including Brazil and the United States. However, it is banned in countries like China and Russia and in the European Union both as an additive as for therapeutic purposes. There are cases in the literature in which residues of beta-adrenergic agonists resulted in human food poisoning. Thus, even in countries where the use of RCT is allowed there are regulated limits. Various analytical methods employing different techniques have been described for determining RCT and its metabolites residues in animal tissue and fluids. For regulatory purposes, both confirmatory and screening tests are needed. In recent literature there are reports of studies for the development of kits for sensitive and selective determination of multi beta-agonists and specific to RCT. However, in none, there were complete and appropriate validations for RCT in swine muscle. This study aimed to validate a commercial kit for screening RCT residues in swine muscle and apply it in a study of the occurrence of RCT residues in pork available on the market of Minas Gerais, Brazil. RCT was added to swine muscle samples at concentrations from 0.029 g/kg to 1.948 g/kg, plus blank, and were analyzed in 30 replicates at each level. Although the kit have not had a satisfactory performance in a quantitative validation approach, it was effective for the detection of RCT residues in pork. False positive rate of zero and 100.0% selectivity rates were estimated for blank samples. Sensitivity rates varied between 22.2% and 100.0%, and reached 100.0% positive results for all levels above 0.244 g/kg, indicating sensitivity. Calculated values of accordance and concordance indicated adequate standardization of the method for level 0 g/kg and above 0.244 g/kg. The limit of detection was estimated in 0.190 g/kg, assuming a 90% reliability. The kit was selective in presence of clenbuterol and robust for the head over head homogenization time, centrifugation time and extract evaporation temperature. The analysis of commercial samples demonstrated the applicability of the method and the occurrence of RCT residue in 73% of analyzed samples.