Determination of antibiotics in raw and uht milk samples by the image forming method of biocrystallization

Abstract

This study aims to investigate a new technique for the antibiotic residue analysis that can able to detect a wide range of antibiotic residues directly in raw and drinking milk by producing reliable and definitive results. "Biocrystallization method" was selected as a new technique to distinguish the raw and UHT milk samples containing antibiotic residues from the antibiotic free ones. This method is based on the crystallographic phenomenon that occurs after adding ionic substances to an aqueous solution of dihydrate CuCl2 and drying in a constant temperature and relative humidity. In this study, the raw and UHT milk samples was screened for antibiotic residues using New SNAP* Beta-Lactam (IDEXX Lab. USA) test kits. Then, the chemical properties of milk samples (e.g. fat%, protein%, lactose%, minerals%, SNF%) were determined. At the same time, biocrystallization method were optimized with antibiotic free raw milk samples. Evaluation of biocrystallograms was performed via a panel. The best biocrystallogram images were obtained for 6 ml of milk samples prepared from 0.5 % milk and 5% CuCl2.2H2O solution by mixing at a ratio of 3 (milk) to 1 (CuCl2.2H2O) dried at 30 °C ,60% relative humidity for 22 h. After optimization, the raw and UHT milk samples were spiked with Penicillin G (2, 4, 8 ppb) and Ampicillin (2, 4, 8 ppb) to generate biocrystallogram images at the optimized conditions. All the images were evaluated with a visual inspection. Biocrystallization method was successfully used to distinguish raw and UHT milk from the samples spiked with Penicillin G and Ampicillin. This method gave better results when discriminating naturally contaminated raw milk from antibiotic free raw milk.