Abstract: Three microbial methods for determinating antibiotic in milk were compared, and the critical parameters of three methods for detecting penicillin G, the residue limits, detection time, cost price and difficulty to operate were studied. At the same time, the study pointed out some disadvantages of TTC method on residue limits, and the tube diffusion method is introduced as a good supplement for the two methods of TTC and AOAC paper disk to determinate β-lactams in milk, inexpensive, quick, simple and convenient, and the low limits of detection for the operation.

Key words: raw milk, penicillin G, detecting method, comparison