Controlling Microbes in Food

Controlling Microbes in Food

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Pathogenic microbes are significant threats to public health. There are two fundamental ways to control microbial contamination of products and processing environments. Both are important. The first involves reducing opportunities for microbes to enter processing environments and come into contact with products

The second involves making the environment for microbes as inhospitable as possible to reduce their numbers and minimize their growth. Note that “control” is a keyword here. It is impossible to completely eliminate all microbes from processing environments and food products. However, it is possible for establishments to implement effective control strategies designed to protect against pathogens and the undesirable effects of spoilage organisms

Prevention of Contamination

It is important to avoid the contamination of meat and poultry whenever possible. This includes inadvertent contamination or cross-contamination from the live animal, processing procedures and equipment, employees, and the environment. Contamination can be minimized or avoided altogether by following appropriate sanitation procedures, good manufacturing procedures (GMPs), and procedures for employee hygiene.

Good sanitary dressing process control measures in slaughter processes not only minimize contamination of carcasses, but also reduce the level of processing environment contamination. Effective pest control can help prevent the introduction of many microbes into the processing environment.

Sound construction of the facility and maintaining its construction will reduce opportunities for microbial contamination of the processing environment. For example, ventilation systems that provide fresh air in and throughout the establishment should be designed and constructed so as to preclude the transfer of contaminated air from the outside to the inside of the establishment

Restriction of Growth

Recognizing that bacteria will be present on meat and poultry, it is important to keep the overall number of bacteria very low to minimize concern about bacterial pathogens as well as spoilage organisms. Making a microbe’s environment as inhospitable as possible can involve a variety of control measures, all of which relate to the FAT TOM factors impacting microbial growth.

Effective procedures for cleaning and sanitizing the facility provide the foundation for controlling microbes. In addition, temperature, acidity, salting and drying, or some combination of these can be used to restrict the growth of pathogens.


Microbes can be found in processing environments, which emphasizes the need for effective sanitation procedures for equipment and floors. Adequate cleaning and sanitizing procedures will help to ensure that little organic matter is available to support microbial growth. Altering the pH of a microbe’s environment may involve the use (and rotation) of acid and alkaline sanitizing agents. Moisture control in the processing environment is an important means of protecting against microbial proliferation.



Temperature controls are important in all classes of product. Maintaining products under refrigeration is one of the most important ways to inhibit microbial growth. Cooking product to temperatures adequate enough to eliminate pathogens of concern is another way to control microbes. Many pathogens are fairly easily destroyed with relatively mild cooking. Bacterial spores and toxins, though, can be very heat resistant. 

Inactivation of spores and some toxins requires thermal processing to high temperatures under pressure as in canning operations. The time it takes for products to reach a particular temperature is also important in inhibiting microbial growth. Chilling raw, heat-treated, and fully-cooked products as rapidly as possible helps to ensure products do not linger in the “danger zone” for too long, which could result in the outgrowth of bacteria, including spore-forming bacteria and toxin-producing bacteria.


Product pH can also be manipulated, though, to inhibit certain microbes in certain products. For example acidifying agents (acidulants) may be added to certain products to reduce pH. Similarly, some products are naturally acidified by the addition of fermentative microbes. Some bacteria can survive in acidic conditions, so fermentation alone cannot be relied upon to completely eliminate all harmful bacteria.

Salting and Drying

Certain production processes involve steps to reduce the water available for microbial growth through the addition of high concentrations of salt or actual drying of the product. Salt and low water activity in a product can be very effective in controlling the growth of some harmful bacteria, but some organisms (e.g., Staphylococcus aureus) can survive in high salt environments.

Vacuum Packaging

Reducing the oxygen level through vacuum packaging processes is a common method of enhancing the shelf life of food products. However, vacuum packaging reduces the growth of mainly spoilage microbes. Pathogenic bacteria, such as Clostridium botulinum and Listeria monocytogenes can still grow in vacuum packaged products.

Given the enhanced shelf life, it is important for processors to consider other measures necessary to protect consumers from pathogens in vacuum packaged products.

Ultimately there is no single method of preventing or controlling microbes in food. It requires a so-called multiple hurdle approach. Fundamentally, this can be represented by compliance with the Sanitation Performance Standards, maintaining effective Sanitation SOPs, and designing and implementing an effective HACCP plan.

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