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Validation of the Time/Temperature Required for the Thermal Destruction of Pathogenic Bacteria in Rendered Animal Products

Investigators
Greene, Annel; Jaing, Xuiping; Bridges, William C
Institutions
Clemson University
Start date
2012
End date
2016
Objective
Validating thermal lethality of rendering processes is needed to ensure destruction of bacterial and viral pathogens in products. A disease outbreak in the animal livestock industry can have serious consequences to the rendering industry as well as the animal agriculture industry. After the recent outbreak of Salmonella in eggs, blame was erroneously assigned to the rendering industry. With the current level of media coverage and rapid methods of disseminating information and misinformation, an outbreak of even a low pathogenicity disease could receive widespread negative publicity. Upon such an outbreak, miscommunication and lack of solid data could lead to economic instability in the rendering industry and its markets. The U.S. and Canadian rendering industry processes more than 59 billion pounds of raw rendering materials annually. By thermally processing and drying the materials, the industry is able to recycle millions of tons of ingredients back into animal feed as well as produce a large number of industrial products such as biodiesel, lubricants, etc. Anecdotal data indicates the rendering industry's thermal processes are very effective in destroying pathogens. However, it is imperative that the rendering industry have conclusive validation data on the effectiveness of rendering to destroy animal disease pathogens to assure customers of product safety. Additionally, it is imperative that accurate test methods are developed to detect these pathogens in high fat rendered materials to prevent false positive and false negative results.

Preliminary test procedures have been developed through earlier studies funded by the rendering industry. This project will build on that knowledge and will validate the thermal destruction of disease entities in rendering materials including Salmonella and Clostridium perfringens. With pending implications for the release of the Food Safety and Modernization Act (FSMA), researchers recognize the renderers' need for information as soon as possible. If this thermal validation study is not conducted, the rendering industry will remain vulnerable to misinformation and false accusations such as generated in the Salmonella in egg outbreak. Providing the validation data along with thermal record-keeping already maintained by the rendering companies will assist in providing the safest animal feed and pet food ingredients possible. Rendering materials contain high levels of fat which complicate thermal death time studies. Preliminary studies conducted in this laboratory have resulted in development of new techniques.

The impact of this study will be a continuing increase in knowledge about thermal death time requirements for pathogenic bacteria in rendered animal co-products. This knowledge will help increase the microbiological safety of pet food which is readily in contact with consumers and is commonly stored inside the home and very often in the kitchen of the home. The knowledge of the thermal death time requirements for pathogenic microorganisms in rendered animal products will also contribute to animal feed safety and ultimately contribute to the overall farm to fork safety of animal products.

More information
Non-Technical Summary:
Validating thermal lethality of rendering processes is needed to ensure destruction of bacterial and viral pathogens in products. A disease outbreak in the animal livestock industry can have serious consequences to the rendering industry as well as the animal agriculture industry. After the recent outbreak of Salmonella in eggs, blame was erroneously assigned to the rendering industry. With the current level of media coverage and rapid methods of disseminating information and misinformation, an outbreak of even a low pathogenicity disease could receive widespread negative publicity. Upon such an outbreak, miscommunication and lack of solid data could lead to economic instability in the rendering industry and its markets. The U.S. and Canadian rendering industry processes more than 59 billion pounds of raw rendering materials annually. By thermally processing and drying the materials, the industry is able to recycle millions of tons of ingredients back into animal feed as well as produce a large number of industrial products such as biodiesel, lubricants, etc. Anecdotal data indicates the rendering industry's thermal processes are very effective in destroying pathogens. However, it is imperative that the rendering industry have conclusive validation data on the effectiveness of rendering to destroy animal disease pathogens to assure customers of product safety. Additionally, it is imperative that accurate test methods are developed to detect these pathogens in high fat rendered materials to prevent false positive and false negative results. Preliminary test procedures have been developed through earlier studies funded by the rendering industry. This project will build on that knowledge and will validate the thermal destruction of disease entities in rendering materials including Salmonella and Clostridium perfringens. With pending implications for the release of the Food Safety and Modernization Act (FSMA), researchers recognize the renderers' need for information as soon as possible. If this thermal validation study is not conducted, the rendering industry will remain vulnerable to misinformation and false accusations such as generated in the Salmonella in egg outbreak. Providing the validation data along with thermal record-keeping already maintained by the rendering companies will assist in providing the safest animal feed and pet food ingredients possible. Rendering materials contain high levels of fat which complicate thermal death time studies. Preliminary studies conducted in this laboratory have resulted in development of new techniques. This knowledge will help increase the microbiological safety of pet food which is readily in contact with consumers and is commonly stored inside the home and very often in the kitchen of the home. The knowledge of the thermal death time requirements for pathogenic microorganisms in rendered animal products will also contribute to animal feed safety and ultimately contribute to the overall farm to fork safety of animal products.

Approach:
Samples of cooked poultry rendering materials (poultry fat and crax as it exits the cooker and press, respectively) will be collected from three rendering companies in the southeastern United States and stored under refrigeration until needed. Materials will be blended in a disinfected commercial food processor for 10 min to reduce particle size. All samples will be analyzed in triplicate for chemical composition (ash, crude fat, crude protein and dry matter) by the Clemson University Agricultural Service laboratory. A cocktail of overnight cultures of Salmonella strains will be prepared tryptic soy broth (TSB). This cocktail will be aseptically added to the rendering materials at an initial concentration of ca. 107 cfu/g or greater, which will be confirmed by enumeration on XLD agar. Samples will include uninoculated controls, inoculated unheated controls and inoculated heated samples. Thermal trials will be conducted in tubes in heated blocks at the minimum temperature and time combination which can be proven achievable within a rendering cooker and then temperature/time conditions will be bracketed upwards to give a wide variety of potential thermal treatment conditions which may occur in the rendering cooker. After thermal treatment, tubes will be plunged into ice to cool. Samples will be analyzed for thermal destruction of Salmonella using a yes/no criteria and enumeration. The procedure will be conducted in triplicate on each of two separate days for all samples. The Salmonella testing proposed in this procedure will not include strain confirmation tests. However, the test is designed to provide a yes/no result for presence/absence of Salmonella and for enumeration. Clostridium perfringens is an organism of concern in rendered animal co-products. A sporeforming organism, C. perfringens is more resistant to heat than Salmonella species but the actual thermal death time has never been ascertained in the rendering material matrix. Upon validation of methodology for use with each microorganism in the rendering materials, thermal trials will be initiated to determine lethality of various temperature/time combinations between 260F and 290F which are typically lower and upper temperatures used in commercial rendering cookers and times ranging from 0 minutes (come-up time) to 40 minutes which represents the lower time factor reported to be used by the rendering industry. The thermal death time trials for each temperature/time condition will be conducted in triplicate on each of three days using various rendering materials from three different rendering facilities and plated in duplicate. Each rendering material will be analyzed for fat, moisture and ash content. Statistical Analysis: Data will be analyzed using a statistical model to include the overall mean and considerations for treatment, specific combinations of treatment and time, plant to plant variation and overall error.

Progress:
2012/01 TO 2012/12
OUTPUTS: The outputs completed during the reporting period include the activities of conducting and analyzing research experiments to determine the thermal death time of Salmonella cholerasuis in a 50% fat and 50% protein/bone rendering material matrix at 240F (116C) across multiple times. Progress reports and presentations concerning the project and its outcomes have been presented to industrial members of the rendering industry in Fall 2012 and Spring 2013.
PARTICIPANTS: M. Melissa Hayes conducted the laboratory research for the project under the guidance of Professor Annel K. Greene. Professor William C. Bridges directed the statistical analysis for the project. The rendering industry through its Fats and Proteins Research Foundation served as a partner organization in providing research funding and samples. The project has provided opportunities for graduate education as well as an increase in the knowledge base of faculty, staff and students concerning the needs of the rendering industry.
TARGET AUDIENCES: The overall target audience for this study is the rendering industry and regulators working to ensure Salmonella free rendered animal feed ingredients. The knowledge increase will allow validation of thermal processes used in rendering cookers to ensure thermal destruction of Salmonella. The rendering industries will be able to utilize this knowledge to further cause a change in knowledge and to build more understanding of microbial destruction in rendering.
PROJECT MODIFICATIONS: The researchers obtained four of the eight species of pathogenic Salmonella species included in the FDA list of Salmonella strains of concern to animal feeds. Salmonella choleraesuis, Salmonella Newport, Salmonella Dublin and Salmonella Enteritidis were used in this study.

IMPACT: In preliminary trials, it was determined to be more time efficient and would provide more information to conduct thermal death time trials on individual species rather than in a four species cocktail. Additionally, the researchers were able to obtain additional species of pathogenic Salmonella species included in the FDA list of eight pathogenic strains of Salmonella of concern to animal feeds. The species analyzed in this study are Salmonella choleraesuis, Salmonella Newport, Salmonella Dublin and Salmonella Enteritidis. The culture of Salmonella choleraesuis was grown in tryptic soy broth, centrifuged and re-suspended to a final concentration of approximately 12 log cfu/g as confirmed by enumeration on XLD agar. The culture was aseptically added to rendering materials to create an initial concentration of ca. 1010 cfu/g. Samples included uninoculated controls, inoculated unheated controls and inoculated heated samples. Each sample was tested in duplicate on each of three days. Thermal trials were conducted in tubes in heated blocks at 240 degrees F (116 degrees C) for various times (0, 15, 30, 60, 90, 120, 180, 240 and 300 sec). Additional control tubes were included for monitoring temperature. After thermal treatment, tubes were placed immediately on ice to cool. Work has been completed the thermal death time analysis at 240 degrees F on Salmonella choleraesuis, in 50% fat beef at treatment times of 0, 15, 30, 60, 90, 120, 180, 240 and 300 seconds. Data indicates some variability in Salmonella thermal destruction and there appears to be heat resistant background organisms present. However, at 240 degrees F for Salmonella choleraesuis, the last positive appeared at 240 seconds on only one day of experimentation; on the other three days of the experiment, Salmonella choleraesuis was destroyed at 0 seconds. Further work is continuing on Salmonella Dublin, Salmonella enteritidus and Salmonella Newport in 50% fat beef at 240 degrees F and on Salmonella choleraesuis, Salmonella Dublin, Salmonella enteritidus and Salmonella Newport in 50% fat poultry at 240 degrees F. Beef fat is a harder fat than poultry fat so it will be interesting to see if type of fat has an impact on thermal death of these pathogenic Salmonella. The eventual goal of the researchers is to develop a table where renderers can look up their tissue type (poultry, beef, pork, mixtures), percentage of fat, and processing temperature and find the minimum amount of time required to kill a particular pathogenis Salmonella. This is very time-consuming and expensive work to conduct but the final results will be a document that will be of great value for validation of processing conditions within each rendering processing plant. The outcome and impact of this phase of the study was development of data points for inclusion in this information table for vailidating rendering thermal processes for killing pathogenic Salmonella.

Funding Source
Nat'l. Inst. of Food and Agriculture
Project source
View this project
Project number
SC-1700460
Accession number
231377
Categories
Bacterial Pathogens
Salmonella
Commodities
Meat, Poultry, Game
Eggs