Analysis of Triphenylmethane Dye Residues and their Leuco-Forms in Frozen Fish by LC-MS/MS, Fish Microbial Quality, and Effect of Immersion in Whole Milk on Dye Removal

摘要

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was validated and used to quantify crystal violet (CV), leucocrystal violet (LCV), malachite green (MG), leucomalachite green (LMG), and brilliant green (BG) residues in frozen fish (121 samples) from various countries, in order to detect the use of prohibited antibiotic dyes in fish for human consumption. The microbial quality of the fish was also assessed along with the effectiveness of a simple treatment with whole fat milk to reduce the levels of CV and LCV contamination. CV and LCV were the only two residues detected. They were found in farmed Pangasius (0.362 to 41.34 g/kg and 0.178 to 10.58 g/kg, respectively) and Tilapia (1.24 to 9.48 g/kg and 1.29 to 2.81 g/kg). Based on aerobic plate count (APC), 74%, 59%, and 55% of the samples of Tilapia fillets (from China) and Pangasius fillets (United Arab Emirates and Vietnam), and 100% and 50% of the skin samples of Hake (Argentina and U.S.A.) were of unacceptable microbial quality (APC 10(7) cfu/g). Human pathogens, namely Escherichia coli, Staphylococcus aureus, and Vibrio spp., were detected in most fish. A significant reduction in CV and LCV concentrations by more than a third was achieved after immersing Pangasius and Tilapia fillets in whole fat milk for 120 minutes. These findings support the necessity of regular inspections and monitoring of CV and other antibiotic dye residues in fish, along with routine assessments of fish microbial quality, in order to protect public health.