Microbial testing in dairy products

Introduction

The vast world of dairy products, from creamy yogurt to aged cheese, is teeming with microscopic life. These microorganisms, collectively known as microbes, play a crucial role in the production, quality, and safety of dairy products. Some are beneficial, like those used in fermentation, while others can pose a threat to food safety, causing spoilage or illness.

Microbial testing

Antibiotics are commonly used in livestock farming to promote growth and prevent diseases. However, improper use or excessive administration can result in residues lingering in meat, milk, and other animal products. When these residues make their way into the human body through consumption, they pose a potential threat by contributing to antibiotic resistance – a global health concern.

Microbial testing acts as the guardian of this microbial ecosystem. It provides a vital tool for dairy producers to ensure the safety and quality of their products by:

Identifying and quantifying the presence of microorganisms: This includes both harmful pathogens like Salmonella and E. coli, as well as beneficial bacteria that contribute to flavor and texture.

Preventing foodborne illness: By detecting and eliminating harmful bacteria, microbial testing helps protect consumers from the dangers of foodborne illness.

Maintaining product quality: Spoilage organisms can cause dairy products to deteriorate, affecting their taste, texture, and shelf life. Microbial testing helps identify and control these organisms, ensuring that consumers have access to fresh, high-quality products.

Promoting beneficial bacteria: Certain beneficial bacteria, such as probiotics, offer health benefits for consumers. Microbial testing helps ensure that these bacteria are present at the appropriate levels in dairy products.

There are a variety of different methods used for microbial testing in dairy products. Some of the most common methods include

Culturable methods:

Traditional plating: This involves spreading a diluted sample of the dairy product onto an agar plate containing nutrients that encourage bacterial growth. Different types of agar can be used to target specific bacteria based on their growth requirements. After incubation, colonies are counted and identified based on their appearance, size, and other characteristics. This method is relatively simple and inexpensive but can be time-consuming and may not detect all bacteria present, particularly slow-growing or stressed organisms.

Most Probable Number (MPN): This method uses a series of tubes containing broth and varying dilutions of the dairy sample. The tubes are then incubated and checked for bacterial growth. The MPN is determined statistically based on the number of positive tubes. This method is more sensitive than traditional plating but requires more materials and expertise.

Molecular methods:

Polymerase Chain Reaction (PCR): This method amplifies specific DNA sequences, enabling the detection of even very low levels of specific bacteria. PCR can be used to target a wide range of organisms, including pathogens and spoilage bacteria. It is highly sensitive and specific, but requires specialized equipment and expertise.

Real-Time PCR: This advanced version of PCR allows for the quantification of bacteria in real-time, providing results within minutes or hours. This method is particularly useful for rapid screening and monitoring.

DNA sequencing: This method identifies the complete DNA sequence of an organism, allowing for precise identification and strain typing. This information can be valuable for tracing the source of contamination and understanding the diversity of microbes present in dairy products.

Rapid methods:

ATP bioluminescence: This method measures the amount of adenosine triphosphate (ATP), a molecule present in all living cells. The higher the ATP level, the higher the microbial load. This method provides rapid results (within minutes) but does not distinguish between different types of microorganisms.

Immunoassays: These methods use antibodies to detect specific antigens on the surface of bacteria. They are highly specific and sensitive and can provide results within minutes to hours.

Flow cytometry: This method uses lasers and fluorescent dyes to analyze individual cells based on their size, shape, and other characteristics. It can be used to rapidly identify and quantify specific bacteria.

The specific methods used for microbial testing will vary depending on the type of dairy product being tested, the target organisms, and the required sensitivity and specificity.

Here is a list of some of the most common microorganisms tested for in dairy products:

Bacteria and the Diseases They Cause

Recall incidents 

A staggering 48% of all food recalls are triggered by the presence of harmful pathogens, including bacteria, parasites, and viruses. These contaminants can cause serious illness, hospitalization, and even death, underscoring the critical importance of food safety measures.

Some of the largest and most devastating food recalls in history have involved pathogen contamination. One such example is the Peanut Corporation of America scandal, where Salmonella-tainted peanut products led to the recall of over 3,200 items, causing significant financial losses and impacting consumers nationwide. Tragically, this incident resulted in 9 reported deaths and over 600 cases of Salmonella sickness across 46 states

Market Overview

In 2022, the global microbiology testing market achieved a valuation of USD 4.9 billion, with projections indicating a significant growth to approximately USD 11.76 billion by 2032. This expansion is anticipated to occur at a Compound Annual Growth Rate (CAGR) of 9.2% from 2023 to 2032. The microbiology testing sector plays a crucial role in the analysis and identification of microorganisms, including bacteria, viruses, fungi, and parasites. Its impact spans across various industries such as healthcare, pharmaceuticals, food and beverage, and environmental monitoring, highlighting its pivotal significance in these diverse sectors.

Standards and Regulations  

Codex Alimentarius Commission (CAC): This international body sets global standards for food safety and quality, including standards for microbiological limits in various foods, including dairy products.

International Dairy Federation (IDF): This organization develops and publishes standards and guidelines for the dairy industry, including microbiological standards for different types of dairy products.

National regulatory bodies: Each country or region also has its own regulatory body responsible for ensuring food safety and setting microbiological standards for dairy products. Examples include the US Food and Drug Administration (FDA), the European Commission, and the Food Safety and Standards Authority of India (FSSAI).

Typical Microbiological Standards

Here are some examples of typical microbiological standards for different types of dairy products:

Milk:

Pasteurized: Total bacteria count: ≤ 20,000/mL, Coliforms: ≤ 10/mL, No Salmonella or E. coli.

Raw: Total bacteria count: ≤ 30,000/mL, Coliforms: ≤ 10/mL, No Salmonella or E. coli.

Cheese:

Pasteurized: Total bacteria count: varies depending on type, Coliforms: ≤ 10/g, No Salmonella or E. coli.

Unpasteurized: Total bacteria count: varies depending on type, Coliforms: ≤ 100/g, No Salmonella or E. coli.

Yogurt:

Total bacteria count: varies depending on type, Coliforms: ≤ 10/g, No Salmonella or E. coli.

Dried milk:

Total bacteria count: ≤ 50,000/g, Coliforms: ≤ 10/g, No Salmonella or E. coli.

These are just a few examples, and the specific standards can vary depending on the type of dairy product, the country, and the intended use of the product.

Importance of Regulations and Standards

Regulations and standards for microbes in dairy products play a vital role in protecting public health and ensuring the quality of dairy products. They help to:

• Reduce the risk of foodborne illness by controlling the levels of pathogenic bacteria.
• Maintain the quality and shelf life of dairy products by controlling spoilage bacteria.
• Promote fair trade by ensuring that all producers comply with the same standards.
• Build consumer confidence in the safety and quality of dairy products.

Codex Alimentarius Commission: https://www.fao.org/fao-who-codexalimentarius/en/

International Dairy Federation: https://fil-idf.org/

US Food and Drug Administration: https://www.fda.gov/food/guidance-documents-regulatory-information-topic-food-and-dietary-supplements/milk-guidance-documents-regulatory-information

European Commission: https://agriculture.ec.europa.eu/farming/animal-products/milk-and-dairy-products_en

Food Safety and Standards Authority of India: https://www.fssai.gov.in/

Mandatory and optional analyses

The analysis of microbes in dairy products is crucial for ensuring their safety and quality. Depending on the regulations and standards applicable, the required analyses can be mandatory or optional. Here's a breakdown of both categories:

Mandatory analyses:

Pathogenic bacteria: This is the most crucial aspect of microbial testing. Mandatory analyses include the detection and quantification of harmful bacteria like Salmonella, E. coli, Listeria monocytogenes, and Staphylococcus aureus. The allowable limits for these pathogens are strictly defined and monitored by regulatory bodies.

Indicator bacteria: These bacteria, although not inherently harmful, indicate poor hygiene practices or contamination during production. Examples include coliforms and Enterobacteriaceae. Their presence and levels are often used to assess the overall hygiene of the dairy processing environment and can trigger further investigations if exceeding established limits.

Total bacterial count (TBC): This analysis measures the overall number of bacteria present in a dairy product, regardless of their species. It provides a general indication of the product's hygiene and shelf life. Depending on the specific product and regulations, maximum allowable levels may be set for the TBC.

Optional analyses:

Spoilage bacteria: While not mandatory, testing for spoilage bacteria like Pseudomonas, Bacillus, and lactic acid bacteria can be valuable for ensuring product quality and shelf life. Exceeding certain levels of these bacteria can lead to off-flavors, texture changes, and reduced shelf life.

Specific spoilage organisms (SSOs): Depending on the type of dairy product and potential risks associated with specific bacteria, optional analyses may target certain SSOs. For example, testing for psychrotrophic bacteria in raw milk can be crucial due to their ability to grow at cold temperatures and cause spoilage during storage.

Antibiotic residues: In some regions, testing for antibiotic residues in dairy products is mandatory or recommended to ensure consumer safety and prevent antimicrobial resistance.

Specific pathogens: Depending on specific risk factors or suspected outbreaks, optional analyses may target additional pathogens beyond the standard ones. This can be particularly relevant for imported products or those associated with specific processing methods.

Eurofins role in microbial testing in dairy products

Eurofins plays a significant role in microbial testing for dairy products globally. With its extensive network of laboratories and expertise in food safety, Eurofins offers a comprehensive range of services for dairy producers, processors, and retailers. Here are some key aspects of Eurofins' involvement in microbial testing for dairy products:

Services offered:

Pathogen detection and quantification: Eurofins tests for a wide range of pathogenic bacteria, including Salmonella, E. coli, Listeria monocytogenes, and Staphylococcus aureus, using advanced methods like PCR and ELISA.

Indicator bacteria analysis: Eurofins measures the levels of coliforms and Enterobacteriaceae to assess overall hygiene practices and potential contamination.

Total bacterial count: Eurofins provides accurate determinations of the total number of bacteria present in dairy products.

Spoilage bacteria analysis: Eurofins identifies and quantifies spoilage bacteria like Pseudomonas, Bacillus, and lactic acid bacteria to predict shelf life and ensure product quality.

Specific spoilage organism (SSO) testing: Eurofins can target specific SSOs based on the type of dairy product and potential risks.

Antibiotic residue analysis: Eurofins helps ensure consumer safety by testing for antibiotic residues in dairy products.

Hygiene checks and environmental monitoring: Eurofins assists dairy producers in maintaining a clean and hygienic production environment through site inspections and airborne microbe measurement.

DNA-based analytical methods: Eurofins utilizes advanced DNA-based techniques for milk authentication and other specific applications.

Benefits of using Eurofins services:

Global network of laboratories: Eurofins provides local access to testing services in over 50 countries, ensuring efficient and timely results.

Expertise and experience: Eurofins has a team of highly skilled and experienced professionals with extensive knowledge in food safety and dairy microbiology.

Accredited laboratories: Eurofins laboratories are accredited to international standards, guaranteeing the accuracy and reliability of test results.

Comprehensive service portfolio: Eurofins offers a one-stop solution for all your dairy product microbial testing needs.

Regulatory compliance: Eurofins keeps abreast of all relevant regulations and standards to ensure your compliance and product safety.

Advanced technology: Eurofins utilizes cutting-edge technology and methodologies for rapid, accurate, and reliable testing.

Overall, Eurofins plays a vital role in ensuring the safety and quality of dairy products by providing comprehensive microbial testing services and supporting dairy producers and processors in meeting regulatory requirements and delivering safe and wholesome products to consumers.

References

1. Hickey CD, Sheehan JJ, Wilkinson MG, Auty MA. Growth and location of bacterial colonies within dairy foods using microscopy techniques: a review. Front Microbiol. 2015 Feb 18;6:99. doi: 10.3389/fmicb.2015.00099. PMID: 25741328; PMCID: PMC4332360.Codex Alimentarius Commission: https://www.fao.org/fao-who-codexalimentarius/en/
2. International Dairy Federation: https://fil-idf.org/
3. US Food and Drug Administration: https://www.fda.gov/food/guidance-documents-regulatory-information-topic-food-and-dietary-supplements/milk-guidance-documents-regulatory-information
4. European Commission: https://agriculture.ec.europa.eu/farming/animal-products/milk-and-dairy-products_en
5. Food Safety and Standards Authority of India: https://www.fssai.gov.in/

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