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Comparative Evaluation of the Difco Disc Assay Method for Detecting Penicillin in Milk and Milk Products

R E Ginn1, Sita Tatini1, V S Packard1

  • 1Dairy Quality Control Institute, Inc., St. Paul, Minnesota 55113 and Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota 55108.

Journal of Food Protection
|February 24, 2019
PubMed

Insights

The Difco disc assay effectively detects penicillin residues in milk, showing higher sensitivity than other methods. This method is reliable for ensuring milk product safety and quality.

Area of Science:

  • Food safety and analytical chemistry.
  • Microbiology and antibiotic residue detection.

Background:

  • Antibiotic residues in milk pose a significant food safety concern.
  • Accurate detection methods are crucial for regulatory compliance and consumer protection.

Purpose of the Study:

  • To evaluate the Difco disc assay for detecting penicillin residues in milk.
  • To compare its performance against Bacillus subtilis disc assay and Sarcina lutea cylinder plate methods.

Main Methods:

  • Comparative analysis of three antibiotic detection methods: Difco disc assay, Bacillus subtilis disc assay, and Sarcina lutea cylinder plate.
  • Analysis of 5200 raw milk samples for penicillin presence.

Main Results:

  • The Difco method detected penicillin down to 0.002 units/ml, utilizing color change and zone of inhibition.
  • Difco identified 0.92% positive samples for penicillin, with 78.4% confirmation by S. lutea.
  • Bacillus subtilis method identified 0.239% positive samples.

Conclusions:

  • The Difco disc assay is an effective and sensitive method for detecting penicillin in raw and finished milk products.
  • It offers improved detection capabilities compared to the Bacillus subtilis method for penicillin residues.

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