This standard specifies the test method for antibiotic residues in fresh milk. This standard is applicable to the test of various commonly used antibiotics that can kill thermophilic lactic streptococci. GB/T 4789.27-2003 Food hygiene microbiological test Test for antibiotic residues in fresh milk GB/T4789.27-2003 Standard download decompression password: www.bzxz.net

ICS07.100.30
National Standard of the People's Republic of China
GB/T4789.27—2003
Replaces GB/T4789.27-1994
Microbiological examination of food hygiene
Examination of residue of antibiotics in fresh milk
Microbiological examination of food hygiene-Examination of residue of antibiotics in fresh milkPromulgated on August 11, 2003
Implementation on January 1, 2004
Ministry of Health of the People's Republic of China
Standardization Administration of the People's Republic of China
GB/T4789.27-—2003
This standard revise GB/T4789.27~—1994 "Microbiological examination of food hygiene-Examination of residue of antibiotics in fresh milk". Compared with GB/T4789.27-1994, this standard has the following major revisions: The format and text of the standard text are revised in accordance with GB/T1.1-2000. 1. Modify and standardize the "equipment and materials" in the original standard. From the date of implementation of this standard, GB/T4789.27-1994 will be abolished at the same time. This standard is proposed and managed by the Ministry of Health of the People's Republic of China. The drafting unit of this standard: Nutrition and Food Safety Institute of China Center for Disease Control and Prevention. The main drafters of this standard: Fu Ping, Ji Rong, Yao Jinghui, Yang Baolan. This standard was first issued in 1984, revised for the first time in 1994, and this is the second revision. 188
1 Scope
Food Hygiene Microbiological Examination
GB/T4789.27-2003
Testing of antibiotic residues in fresh milkwwW.bzxz.Net
This standard specifies the test method for antibiotic residues in fresh milk. This standard applies to the test of various commonly used antibiotics that can kill thermophilic lactic acid streptococci. 2
Equipment and materials
2.1 Refrigerator: 4℃~-20℃.
2.2 Constant temperature incubator: 36℃±1℃.
2.3 Constant temperature water bath: 36℃±1℃, 79℃1℃. Tray torsion balance: 0g~100g, accuracy to 0.01g. 2.4
2.5 Sterilized pipette: 1mL (with 0.01mL scale) 10mL (with 0.1mL scale). 2.6 Sterilized test tube: 16mm×160mm.
100℃ thermometer.
2.8 Crayons.
3 Bacterial strains, culture media and reagents
3.1 Bacterial strain: thermophilic lactic acid streptococci.
3.2 Skim milk: sterilize at 113℃ for 20min. 3.34% 2,35-triphenyltetrazolium chloride (TTC) aqueous solution: weigh 1g TTC, dissolve in 5mL sterile distilled water, store in a brown bottle at 7℃ refrigerator, dilute to five times with sterile distilled water before use. If the solution turns jade or light brown, it cannot be used. 4 Test procedure
See Figure 1 for the test procedure for antibiotic residues in fresh milk. Test sample
80, heat for 5min
Cool below 37℃
Add bacterial solution, bath in 36±1℃ water for 2h
Add TTC indicator, bath in 36±1℃ water for 30min, no color
Colored
Antibiotic negative
Bath in 36±1℃ water for 30min
No color
Antibiotic positive
Antibiotic negative
GB/T4789.27—2003
5 Operating steps
5.1 Preparation of bacterial solution: Transfer the bacterial strain to skim milk, culture it at 36℃±1℃ for 15h, and then dilute it with sterilized skim milk in a 1:1 ratio for standby use. 5.2 Take 9mL of the test sample and place it in a 16mm×160mm test tube. Heat it in a water bath at 80℃ for 5min, cool it to below 37℃, add 1mL of bacterial solution, and culture it in a water bath at 36℃±1℃ for 2h. Add 0.3mL of TTC and culture it in a water bath at 36℃±1℃ for 30min. If it is positive, culture it in a water bath for another 30min for a second observation. Make two copies of each test sample, and make one copy of each negative and positive control. The positive control tube uses 8mL of milk without antibiotics, antibiotics, bacterial solution and TTC. The negative control tube uses 9mL of milk without antibiotics, bacterial solution and TTC. 5.3 Judgment method: Culture it accurately for 30min and observe the results. If it is positive, continue to culture it for another 30min for a second observation. Observe quickly to avoid interference caused by long-term light exposure. If there are antibiotics in the milk, although bacterial solution culture is added to the test sample, the growth of bacteria is inhibited, so the indicator TTC is not reduced and no color is developed. On the contrary, if there is no antibiotic present, the bacteria will proliferate when added, and TTC will be reduced and appear red. That is to say, the sample is positive when it is the original color of milk, and negative when it is red. See Table 1 and Table 2 for details. Table 1 Judgment standard of color development state
Color development state
No color
Reddish
Pink-red
Antibiotic name
Penicillin
Gentamicin
Canabinol
Table 2 Sensitivity of detecting various antibiotics
Minimum detection amount
0.004 unit
0.5 unit
0.4 unit
5 unit
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