This standard specifies method for examination of antibiotic residue in fresh milk.
Method I of this standard is applicable to the examination of antibiotics inhibiting streptococcus thermophilus in fresh milk; Method II is applicable to the examination of antibiotics inhibiting bacillus stearothermophilus var.calidola-ctis in fresh milk and it is also applicable to the examination of antibiotics in reconstituted milk, sterilization milk and milk powder.
Method I Streptococcus Thermophilus Inhibition Method
2 Principle
After the sample is subjected to sterilization at 80℃, add bacterium solution of streptococcus thermophilus into it. Streptococcus thermophilus begins to proliferate after being cultured for a certain period. Then add metabolic substrate 2, 3, 5- triphenyl tetrazolium chloride (TTC); if this sample contains no antibiotic or the antibiotic concentration is lower than the detection limit, streptococcus thermophilus will continue to proliferate and reduce TTC to red substance. Otherwise, if the sample contains bacteriostat higher than the detection limit, streptococcus thermophilus will be inhibited, thus the indicator TTC will not be reduced and will keep the original color.
