Module 4. Microbiological risk profile and safety criteria for dairy products

Lesson 18


18.1 Introduction

Food Safety and Standards Authority of India has the responsibility for protecting the health and safety of consumers through the development of food standards. The development through the chain of Primary Production and Processing (PPP) standards require thorough assessment of risk to public health and safety. Codex defines the term risk as ‘a function of the probability of an adverse health effect and the severity of that effect, consequential to a hazard in food’. Risk profiling is defined by FAO/ WHO as the process of describing a food safety problem and its context in order to identify those elements of the hazard or risk relevant to various risk management decisions. Risk assessment is a scientific process undertaken to characterize the risk to public health and safety posed by food-borne hazards associated with a food commodity.

There are a number of tools to assess risks to public health and safety, including risk profiling, quantitative and qualitative risk assessments and scientific evaluations. Risk profile identifies and examines where biohazard may enter the dairy supply chain from the primary produce to processed food. The application of these tools to the assessment of the risks to public health and safety is dependent on the purpose of the assessment and on the availability, quality and quantity of relevant data. One needs to follow established international guidelines and incorporate elements of the CAC when undertaking risk profiles, risk assessment and other scientific evaluations. Guidance for undertaking risk assessments has been drafted internationally by the FAO and WHO.

In assessing risks to public health and safety available scientific data concerning the safety of the commodity under consideration and the properties of the hazard are evaluated. This requires utilization of relevant scientific data and includes procedures to address uncertainty and variability in the conclusions drawn from the data, i.e. consideration of the relevance and quality of data and the veracity of its source.

The outcome of any assessment of risks to public health and safety may include a statement on the probability and severity of an adverse health effect due to the consumption of a food containing a particular biological, chemical or physical agent. An assessment may also identify where in the production chain controls over hazards will have the greatest impact on minimizing risk, i.e. informing the risk managers where intervention will be most effective. The outcomes of the assessing risks to public health and safety for dairy products are used to inform risk management decisions.

18.2 Microbiological Risk Profile

The assessment of risks to public health and safety from microbiological hazards in milk and milk products has been undertaken in the form of a microbiological risk profile. It provides a broad overview of risks associated with consumption of dairy products. The risk profile identifies key food safety hazards and assesses where in the primary production and processing supply chain these hazards might be introduced, increased, reduced or eliminated.

18.2.1 Scope and purpose

The purpose of the risk profile in dairy products is to provide an objective analysis of relevant scientific data and information to identify the public health and safety risks associated with dairy products. This will enable risk managers to consider the risks associated with dairy products and the reductions in risk that may be achieved with various production and process control options. The risk profile may also identify the need for more detailed microbiological risk assessments for specific dairy commodities like dairy products prepared from raw milk especially cheese. The microbiological risk profile identifies and examines hazards along the dairy supply chain from milk production through to consumption of dairy products and has considered the relevant inputs into the dairy primary production and processing chain. The risk profile encompasses the following elements:
  1. Identification and description of the micro-organisms those may be associated with dairy products including key attributes of each organism and its public health impact (hazard identification/hazard characterization).
  2. Examination of prevalence and concentration data on potential hazards from products along the entire dairy food chain.
  3. Examination of epidemiological data (domestic and international) related to the consumption of dairy products.
This risk profile identifies the microbiological public health and safety risks associated with dairy products. In compiling the risk profile, a wide range of scientific literature, data and information should be reviewed and evaluated. A broad range of microorganisms need to be considered in this assessment. The microorganisms should be representative of those that may be present in raw milk, either directly transmitted via the mammary gland or via faecal/ environmental contamination. In addition, micro-organisms that originate from the milking environment and/ or post-pasteurization contamination should also be considered. When examining each dairy commodity category, only those potential pathogens relevant to the commodity being evaluated should be assessed. The estimate of the severity of adverse health effects caused by a food-borne agent may be based on the ranking scheme for food-borne pathogens and toxins described by the International Commission on Microbiological Specifications for Foods. The ICMSF ranking scheme categorizes hazards by the severity of the threat they pose to human health, taking into consideration the: i) likely duration of illness, ii) likelihood of death, and iii) potential for ongoing adverse health effects. The severity of adverse health effects caused by a hazard may be ranked as moderate, serious or severe according to the following definitions:


Under the ICMSF ranking, severe hazards can further be divided into those applying to the general population and those applying to specific sub-populations, that is, susceptible individuals (for example, the very young and old, the immuno-compromised, and pregnant women and their unborn children). This takes into account those situations where a hazard considered to be of moderate or serious to the general population may cause a severe illness in certain susceptible sub-populations. A brief summary of the micro-organisms to be generally looked for their severity of associated illness linked with dairy products and the availability of epidemiological data is depicted in Table 18.1.

Table 18.1 Summary of microorganisms to be generally considered in the risk profile


18.3 Grouping of Dairy Commodities

For the purpose of this profile, dairy commodities may be grouped into broad categories as follows:
  1. Milk and cream
  2. Butter and butter products
  3. Concentrated milk products
  4. Dried milk powders
  5. Infant formulae
  6. Colostrum
  7. Ice-cream
  8. Dairy deserts
  9. Dairy-based dips
  10. Cultured and fermented milk products
  11. Cheese
  12. Indigenous dairy products
  13. Casein, whey products and other functional milk derivatives
18.4 Risk Ranking of Dairy Products

The actual ranking of the dairy products is quite variable. Once a shelf-stable UHT product is opened, it may become contaminated and when subjected to temperature abuse it could become a high-risk food. In contrast, the low pH and low water activity of extra hard cheese means it will be very robust and unlikely to support the growth of any pathogen that adventitiously contaminates the surface. Dried milk powders and infant formulae are inherently stable products due to their low water activity, however, these products may be prone to contamination and upon reconstitution become higher risk, especially if improperly reconstituted and stored. Dairy products likely to support the growth of pathogens and prone to contamination after pasteurization, may be categorized as higher risk than other dairy products, while dairy products that are inherently stable with respect to pathogens, if correctly formulated, can be classified as low risk (Table 18.2 and Fig. 18.1).

Table 18.2 Risk ranking of dairy products



Fig. 18.1 Graphical presentation of relative risk ranking of dairy products

18.5 Risk Management Issues and Control Strategies for Dairy Products

The critical factors having the most significant impact on the safety of processed dairy products are as follows:
  1. The quality of raw materials
  2. Correct formulation
  3. Effective processing
  4. The prevention of recontamination of products
  5. Maintenance of temperature control through the dairy supply chain
While pathogenic microorganisms may contaminate raw milk supplies, pasteurization is a very effective Critical Control Point (CCP) in eliminating pathogens; good manufacturing practices must also be employed to ensure that post-pasteurisation contamination does not occur. The effectiveness of pasteurization is dependent upon the microbiological status of the incoming raw milk. Control measures at the primary production level involve minimizing the likelihood of microbiological hazards contaminating the raw milk. This is achieved through the implementation of a food safety program incorporating GAP. These measures are effective in reducing the microbial load of milk being sent for processing.

However, should microbial contamination of raw milk occur, it is critical that milk is stored at a temperature that minimizes the opportunity for the bacteria to multiply. Temperature abuse of the milk may allow growth of pathogenic bacteria to the extent where the pasteurization process may not eliminate all pathogenic bacteria and/or toxins. Aflatoxins can be formed and ingested by dairy cattle during feeding eventually contaminating the milk. Aflatoxin contamination of milk is more common where intensive supplementary feeding of dairy herds is conducted.

18.5.1 Correct formulation

Ingredients used in the manufacture of dairy products that are added post pasteurization must be of a high microbiological standard. Many non-dairy ingredients added to ice-cream mix after heat treatment include fruits (canned, fresh, or frozen and usually in concentrated sugar syrups), nuts, chocolate, pieces of toffee and biscuit, colors and flavors. These ingredients and those added to other dairy products such as yoghurt, dairy desserts, dairy dips and cheese may introduce pathogens into the product.

The addition of ingredients added after pasteurization was identified as a high risk factor and was recommended that dairy products with these additions (e.g. ice-cream and cheeses) be moved into the high risk category and the finished product be subject to additional end product microbiological analysis. The microbial quality of dry-blended ingredients into infant formula was identified as a significant source of contamination as there is no heat treatment to destroy bacteria in the final product.

18.5.2 Effective processing (pasteurization)

Dairy processing facilities primarily use High Temperature Short Time (HTST) pasteurization (minimum 72°C for 15 seconds) or batch pasteurization (minimum 65°C for 30 minutes) and then rapid cooling to 7-8°C to eliminate the pathogens of concern in milk. However, most factories actually heat the milk to higher temperatures and hold it for a longer time period as an in-built safety margin. In most cases milk and dairy products are consumed as RTE foods and will readily support the growth of any contaminating microorganism. In the past, the dairy industry has been subjected to a high level of food safety regulation ensuring high levels of hygiene and sanitation are maintained. The pasteurization process eliminates all pathogenic bacteria found in raw milk, with the exception of the spore forming bacteria B. cereus and C. perfringens.

18.5.3 The prevention of recontamination of product

Post-pasteurization contamination can pose a major problem where good manufacturing practices are not employed. Pathogenic microorganisms can be introduced into a dairy processing environment with raw milk. Once these organisms gain access to the processing plant the presence of nutrients and moisture can allow not only for survival but also the multiplication of these organisms. The application of food safety programs including elements of GMP and GHP are critical to limit the potential for pathogens to contaminate dairy products after pasteurization. The primary organisms of concern are Listeria monocytogenes for most dairy products and Salmonella in dried milk products.

18.5.4 Maintenance of temperature control through the dairy supply chain

The intrinsic nature of many dairy products means they will support the growth of pathogenic bacteria that may contaminate the product. This categorizes these products as ‘potentially hazardous foods’. Exception to this are products such as yoghurt and hard cheeses (low pH) and ice- cream (stored frozen). As these are potentially hazardous foods maintenance of temperature control through the dairy supply chain is critical to ensure these foods remain safe and suitable.

Notwithstanding the above there is need for ongoing vigilance and further development of safety control measures to counter the emergence of new pathogens and the re-emergence of traditional pathogens in various foods. These organisms often occupy specific environmental niches and may arise through changing technologies, methods of food handling and preparation, dietary habits and population. Post-processing contamination in plant and the maintenance of control over contamination and storage conditions during transport, retail display and home use remain major factors impacting on the safety of dairy products.
Last modified: Saturday, 29 September 2012, 9:28 AM