Biological Hazards: Identification and control

By Ansen Pond, PhD
Director of Quality Assurance, Pilgrim’s


For more than 100 years, the rendering process has been utilized to convert animal by-products into valuable animal food ingredients. Each day, the rendering industry processes millions of pounds of raw materials that contain high levels of biological hazards, which are biological substances that pose a threat to the health of a living organism. Examples of a few biological hazards include bacteria, viruses, molds, fungi, and prions.

The rendering process destroys most biological hazards, reducing the risk of spreading animal disease. The destruction of these hazards, such as bacteria and viruses, is accredited to the extremely high cooking temperatures – more than 230 degrees Fahrenheit (F) – used by the industry to destroy biological hazards, evaporate moisture, and separate liquid fat from the solid materials. Although many people think the high temperatures are targeted to destroy biological hazards, the reality is that fat is more valuable than protein and obtaining high yields of fat is directly related to the high temperature of the cooking process. The higher the temperature of the material, the easier it is to press the fat out. Although destroying biological hazards is the highest priority, it could be done at a much lower temperature. Due to these extremely high temperatures, the history of utilizing rendered products as valuable nutrients in animal diets has been recognized as safe.

For many years the rendering industry had little need to conduct research on biological hazards because there were no significant industry-wide problems associated with rendered products. However, over the last 20 years this type of research has become increasingly important.

On December 23, 1993, the first case of bovine spongiform encephalopathy was identified in the United States. This led the Food and Drug Administration (FDA) to implement laws that restricted the use of certain ruminant proteins due to a prion that is now widely considered a biological hazard. During that time, the rendering industry was heavily engaged in research to defend the safe use of meat and bone meal. Renderers also initiated one of the most progressive movements in the history of animal food by implementing food safety programs and hazard analysis and critical control point-like principles in the Rendering Code of Practice.

A few years later, Salmonella re-took center stage as FDA focused resources to prevent the spread of Salmonella in animal food. Research indicated that certain serotypes of Salmonella were hazardous to the health of specific animal species so FDA released guidance documents in 2013 that essentially made eight serotypes adulterants in livestock food and all serotypes of Salmonella adulterants in pet food. Due to this, the rendering industry initiated multiple research projects that have led to a greater understanding of Salmonella in rendered products.

Additionally, animal agriculture has faced outbreaks of porcine epidemic diarrhea virus (PEDV) and highly pathogenic avian influenza (HPAI). Although the spread of PEDV and HPAI were not directly linked to rendered ingredients, the industry conducted research to verify that the rendering process was sufficient in destroying these viruses. Most recently, FDA’s Food Safety Modernization Act (FSMA) has increased concern regarding biological hazards because it requires that most animal food processing facilities conduct a comprehensive hazard analysis of all chemical, physical, and biological hazards for ingredients and processes used in the manufacturing of animal food. This movement has led to additional industry research to prove the safety of rendered ingredients.

The rendering industry has invested more resources over the past 10 years to better understand biological hazards than any other animal food organization. In addition, the National Renderers Association Animal Protein Producers Industry (APPI) Committee has had an industry testing program in place for over 30 years that now has an impressive microbiological data set on rendered meals. This data has been used to better understand problems and advance improvements in processing facilities. These achievements are due to a history of forward thinkers who understood that ignorance was not an excuse and good science leads to problem solving and innovation.

It was very important to the rendering industry and APPI to validate the cooking temperatures utilized in rendering. With over 100 years of successful manufacturing, there was no doubt the temperatures were sufficient but scientific proof was needed due to FSMA requiring validations such as preventive controls. FSMA requires most facilities that process, pack, or hold animal food to conduct a hazard analysis and implement preventive controls to control hazards. In most cases, rendering facilities will identify pathogens such as Salmonella as hazards in their raw material. This will require these facilities to implement a preventive control to sufficiently control the hazard. These facilities will likely use the cooking process as the preventive control. FSMA also requires that the preventive control be validated to ensure the proper parameters (time/temperature combinations) are set to control the hazard.

In 2015, three research projects were funded by the Fats and Proteins Research Foundation (FPRF) to determine what parameters were appropriate to eliminate Salmonella as a hazard in various raw materials utilized in rendering. These projects took place at Texas Tech University, Texas A&M University, and Colorado State University. Texas Tech focused on validating temperatures for raw beef materials, Texas A&M examined raw poultry materials, and Colorado State concentrated on used cooking oil. This was a challenging task because most validation studies are specific to one process and it is very difficult to apply the same validation to different processes. The rendering industry utilizes diverse cooking processes, temperatures, and raw material sources so a robust validation was designed by researchers and industry members to provide a set of data that is applicable across the industry.

The idea was to create a cooking chart that references different time and temperature combinations to achieve varying levels of Salmonella destruction. In order to apply these standards across the industry, the researchers needed to study high-risk raw materials, which included materials that protected Salmonella from heat. Fat and moisture content in the raw materials are the most influential factors in destroying Salmonella with heat. Fat acts as an insulator and protects bacteria from heat while high moisture content improves the destruction of bacteria. Due to these factors, the researchers targeted high fat and low moisture raw materials to conduct the research experiments. Additionally, with over 2,600 serotypes of Salmonella, the researchers utilized the most heat-resistant strain known to ensure the data would be sufficient for all Salmonella serotypes.

The studies were successful and determined that the time and temperature combinations to eliminate a very heat-resistant Salmonella from a high-risk raw material are much lower and faster than normal processing parameters. A normal industry cooking time and temperature combination is between 20 and 30 minutes at 260 degrees F. These data revealed there is an instantaneous seven to nine log reduction at lower temperatures. Overall, the rendering cooking process is very effective and now the industry has the data to prove it. If you are interested in receiving a copy of this research, please contact FPRF.

Although the cooking temperatures are sufficient for killing Salmonella in raw material, the APPI data indicates low levels of Salmonella contamination in finished meals that is similar to many other feed ingredients. This is believed to be due to the recontamination of Salmonella post-cooking. Many rendering facilities were not originally designed to keep products free of bacteria after cooking, but measures can be taken to reduce the risk of recontamination. All bacteria need some amount of moisture to live and grow, so the most important thing is to keep moisture out of the post-cooking areas. Several ways to help reduce the risk of recontamination are listed below:

• When water is used to lubricate the press, be sure the water is appropriate for its intended use. FSMA specifies that water may be used but it may not increase the contamination level of the food or food contact surfaces. Many facilities are testing press water for generic E. coli and Enterobacteriaceae (EBAC) to verify safety.

• If augers and drags are located outside and their seals on the lids are not effective, rain water may get into the process and allow bacteria to grow. Be sure to check seals and verify control.

• Silos and storage bins outside of the facility should be inspected regularly to ensure they are sealed and free of leaks.

• Transitions between augers and drags are a typical place for meal to build up. These areas could be a source of microbial contamination, especially if water is introduced. A cleaning frequency should be implemented.

• Bulk trailers should be dry prior to loading and the tarp cover should be sufficient to reduce the introduction of moisture. Additionally, the previous load contents should be appropriate.

Keep in mind FSMA stipulates that products containing a hazard requiring a preventive control must be controlled at the facility or downstream (i.e., pet food customer). If meals have the probability to be recontaminated with Salmonella and the product will be used in pet food, the hazard should be controlled by the rendering plant or downstream. This is because all serotypes of Salmonella are considered hazards requiring a preventive control in pet food so any recontamination of Salmonella is a concern.

FSMA states that if a processor is relying on someone downstream (i.e., customer) to control a hazard, the documentation accompanying the load must include a statement such as “not processed to control (the identified hazard).” Additionally, starting in September 2018, documentation that the customer accepts responsibility for the hazard is also required. This should not be an issue as pet food companies typically use the extruding process as their preventive control to control pathogens of concern.

As stated previously, there are only eight serotypes of Salmonella that FDA has identified as hazards in livestock food. The rendering industry has collected data proving that the probability of these eight serotypes of Salmonella is very low in rendered meals. Therefore, the meals used in livestock food should not need an additional preventive control.

Fats produced from rendered products do not have an extensive history with Salmonella. The ability for bacteria to survive and grow in high fat products was not considered likely until a Salmonella outbreak in 2009 when over 700 people in the Untied States became ill due to contaminated peanut butter. Until this point, products with high fat content were not considered high risk.

High fat products now pose some of the most difficult challenges because it has been found that bacteria such as Salmonella can survive. Additionally, due to the high fat content the bacteria become heat resistant because fat insulates them during the heating process. This is an area that is being heavily explored by the scientific community and is one that may pose a risk to rendered fat if used in pet food as a palatant on kibble. Applying palatants to kibble often occurs after the extruding process, which serves as a preventive control to destroy pathogens of concern. This is why fat recontaminated with Salmonella may be a concern for pet food companies. There are several areas where the recontamination of Salmonella in fat may be possible. Following are several ways to help reduce the risk of recontamination:

• When water is used to clean the centrifuge, be sure that the water is appropriate for its intended use. FSMA specifies that water may be used but it may not increase the contamination level of the food or food contact surfaces. Many facilities are testing water for generic E. coli and EBAC to verify safety.

• Fat holding tanks at the rendering plant are vented. If not properly vented, air from the environment could contaminate the product.

• Fat is often filtered prior to loading tankers. Be sure not to contaminate the filters while replacing them and store the clean filters in appropriate locations where contamination is not possible.

• Loading hoses should be stored off the ground and in dedicated locations so they do not become contaminated by the environment.

• Bulk tankers should be dry prior to loading. Additionally, the previous load contents should be appropriate.

As discussed above, product that has the potential to become contaminated by a hazard must be controlled by a preventive control. Rendered products such as fat used in livestock food should not need an additional preventive control because data proves the probability of the eight Salmonella serotypes of concern is very low. However, the recontamination of Salmonella poses an issue for fat used in pet food because all Salmonella serotypes are considered adulterants and fat is applied to kibble after the pet food company’s preventive control. This means the recontamination of Salmonella must be controlled by the renderer or the product must be labeled “not processed to control the recontamination of _Salmonella_” (or something similar) and controlled downstream at the pet food facility with an additional preventive control.

Many, but not all, pet food facilities have implemented preventive controls such as organic acid treatments to control the recontamination of Salmonella at their facilities. Some pet food companies are relying on the rendering facility to supply a pathogen-free product. This is a challenging task that FDA takes very seriously. If a renderer decides to take on this legal liability, FDA will likely require the use of sanitation preventive controls and environmental monitoring for Salmonella at the rendering facility to ensure product does not become recontaminated after the cooking process. FDA also requires the product stay free of pathogens during the transportation process, an unrealistic expectation due to the nature of how most bulk materials are handled and transported, which exposes them to the environment. Due to this, the majority of renderers, if not all, will choose to rely on the customer to control any potential recontamination.

There is no doubt the rendering process sufficiently destroys biological hazards in raw materials but the potential for recontamination does exist. Although the probability of recontamination is low, when dealing with a standard that requires pet food product to be Salmonella free, it is difficult to accept full responsibility. Regardless of one’s opinion, it is important to have a competent food safety team to analyze the process, ingredients, and limitations when it comes to identifying biological hazards.


October 2017 RENDER | back