Abstract
Cleaning and disinfection of dairy equipment is essential to ensure the hygienic quality of milk.
Occasionally, some farmers use washing-up liquids and disinfectants for home use, especially when
cleaning procedures are carried out manually. Residues of detergents and disinfectants in milk may
interfere with the response of microbial inhibitor tests used for screening antibiotics in milk. Therefore,
the aim of this study was to evaluate the interference of non-specific detergents in screening tests
(BRT MRL; Delvotest SP-NT MCS; Eclipse 100) for goats milk. Twelve replicates of eight concentrations
of five washing-up liquids (01%) and one disinfectant (01%) were analysed. The results showed that
the presence of washing-up liquids at concentrations of ≥1 ml/l leads to positive results in microbial
tests. In particular, the product containing sodium laureth sulphate and ethanol produced the largest
number of positive outcomes. The presence of disinfectant based on sodium hypochlorite did not
affect the test response. The detection capabilities of microbial inhibitor tests for penicillins were also
studied in milk with and without cleaning products, calculating the doseresponse curve with eight
concentrations of amoxicillin, ampicillin, benzylpenicillin and cloxacillin, respectively. The detection
limits of the screening tests for penicillins were not modified substantially by the cleaning product
based on sodium laureth sulphate and ethanol. Residues of cleaning agents in milk can be avoided
when specific detergents and disinfectants for milking equipment are used and good cleaning
practices are applied.