Farmers, dairy processors and regulatory authorities across the dairy value chain must work together to avoid dangerous levels of antibiotics in milk products. Various types of tests must be conducted at different points throughout the dairy production and supply chain.
Proper awareness of which antibiotic test to employ and when this should be done is challenging, often involving difficult decisions with opposing factors ranging from compliance with local regulations to market pressures around production speed.
Stakeholders must choose between rapid test, semi-quantification or full quantification methods in order to ensure the quality of milk products as they are passed from the farm to the final product.
Dairy cows treated with antibiotics are taken out of milking rotation to ensure overall milk product integrity. This also represents a financial loss to the farmer, creating an urgency to get the cow back into the milking rotation quickly.
Rigorous testing procedures are required to ensure these cows are not returned to production too early, resulting in tainted milk entering the commercial market. Farmers must make use of reliable, straightforward milk testing methods to confirm that an antibiotic has been completely removed from a cow’s system.
Milk collected from a dairy farm is typically combined with other farms’ milk into a single tanker. Production efficacy gained from processing a single large batch can be compromised from potential antibiotic contamination from just one cow.
Processing companies hold back samples of milk from each individual farm to help mitigate and detect any potential contamination source.
Should testing on the tanker highlight unsafe levels of antibiotics, individual samples can be tested so that the antibiotics can be traced back to the contamination source.
The Importance of Rapid Testing
Rapid, high throughput screening methods are found at various stages of the milk product’s journey:
- At the farm
- On the truck
- At regional or national borders
- At the point of delivery
- During pre-processing at the plant
Each checkpoint will focus on a specific attribute, necessitating a specific approach. For example, testing on trucks requires the use of space-saving tools that are frequently handheld and battery operated.
Where contamination is suspected, milk may require analysis via high-sensitivity instruments to determine the precise antibiotic contaminants and their concentrations. This information can help pinpoint how and where the issue occurred.
Accommodating Wide-ranging Regulations
Rapid testing undertaken at farms and processing plants may be sensitive enough for screening at antibiotics’ maximum residue levels (MRLs), but a notable lack of global standards harmonization means that not all rapid tests are universally applicable in every region.
Several national and international organizations set the MRLs of antibiotics in milk differently.
The EU enforces regulations requiring the detection of 15 different ß-lactam antibiotics at thresholds different to the 6 ß-lactams that the regulated by the USA. Standards outlined in the UN’s Codex Alimentarius differ further, and even countries that typically follow international standards may present some exceptions for certain antibiotics.
These contrasting regulations mean that businesses engaged in the dairy value chain must be constantly aware of where a product is being transported to and from, ensuring that appropriate testing is in place to conform to local regulations.
Approaches to Testing
Digital readers are a key element in the transparency and traceability of supply chains. Images of test strips from rapid testing should be uploaded to a dairy’s quality management system in order to maintain sufficient records of product quality for audits and inspections.
As well as the ability to store results, digital readers help to minimize human error. For example, if a milk producer and a milk transporter disagree on the visual results of an antibiotic test, digital readers can eliminate this ambiguity and ensure the provision of a documented, reliable reading.
Manufacturers of fermented dairy products such as yogurt and sour cream must verify the quality of milk purchased. Many related processes and final products deliberately include bacterial cultures, so it is vital that no antibiotics are present that could potentially compromise these delicate ecosystems.
Available strip test kits can confirm the presence of over 20 major antibiotics. These are frequently employed in the verification of incoming milk quality prior to the fermentation processes, requiring no scientific expertise to use. These tests help afford manufacturers of milk-based products peace of mind.
Use of Semi-Quantitative Testing
Some situations require regulations to define tighter thresholds of a single antibiotic or the reporting of concentrations of all individual antibiotics.
Semi-quantitative ELISA-based screening methods are often an ideal solution in these scenarios, while Immunoassays coupled with automated plate readers offer a high throughput method ideal for evaluating entire groups of antibiotic families in milk across a wide dynamic range.
This technique involves milk samples being placed on a plate coated with antibiotic-specific antibodies. Scanning this plate in a spectroscopy-based plate reader allows milk testers to measure fluorescence and construct standard curves for concentrations of various antibiotics present in the samples.
Positive results identified via these methods must be confirmed using high-sensitivity analysis, but it remains the most rapid and cost-effective means of measuring concentrations of specific antibiotics in milk.
Standard ELISA protocols require a degree of manual labor which can impact throughput – a critical consideration in busy, often overwhelmed, food testing laboratories.
Any reduction in hands-on experimental time via rapid sample preparation protocols and automated microplate readers is beneficial when looking to use ELISA protocols for antibiotic testing.
Fully Quantitative Testing
In cases where routine rapid testing or semi-quantitative testing identifies antibiotic contamination in the dairy supply chain, there is a need for further investigation using fully quantitative analytical methods, such as liquid chromatography tandem mass spectrometry (LC/MS/MS).
These analytical techniques have larger footprints than rapid testing methods. They also exhibit longer run-times and are subject to higher costs. Despite this, they remain unmatched in terms of their capacity to accurately determine analyte concentrations.
LC/MS/MS represents the most dependable means of identifying and quantifying antibiotics in the dairy supply chain and is a key tool in central food agencies and contract testing laboratories alike.
It may also be necessary to test milk and milk products using LC/MS/MS when operating in countries whose regulations include exceptionally low MRLs for specific antibiotics or Minimum Required Performance Limits (MRPLs) for prohibited drugs.
Rapid testing via strips or ELISA methodologies does not provide adequate sensitivity to ensure regulatory compliance, meaning that testing and analysis must be outsourced to contract laboratories.
These instruments are also able to measure drug metabolites and additional analytes (for example, aflatoxins and pesticides) in the same test – a further benefit to central food testing laboratories.
Conclusion
The suitability of tests for antibiotics in dairy products is highly dependent on the specific requirements of the testing site. It is imperative that facilities have a broad understanding of the reason for running specific tests and what results are required.
In terms of testing milk for antibiotics, rapid, semi-quantitative and fully quantitative methods each present case-specific advantages and disadvantages.
The selection of an appropriate method is often influenced by user expertise, available space and a careful balance between accuracy and speed requirements.
Implementing the right solutions at each point in the value chain improves the efficiency and reliability of the often daunting task of antibiotic testing.
This is key to ensuring regulatory compliance and the prevention of unintentional food fraud, as well as in the maintenance of consumer trust and the mitigation of risk to public health.
References
- Commission Regulation (EU) on pharmacologically active substances and their classification regarding maximum residue limits in foodstuffs of animal origin. EU Commission
- Milk Drug Residue Sampling Survey, FDA
- Index of Veterinary Drugs, Food and Agriculture Organization of the United Nations
This information has been sourced, reviewed and adapted from materials provided by PerkinElmer Food Safety and Quality.
For more information on this source, please visit PerkinElmer Food Safety and Quality.