By Gary G. Pearl, D.V.M.
President
Fats and Proteins Research Foundation
The overall class of lipids is also common relative to their biosecurity properties. Rendered animal products including yellow grease/used cooking oils are subjected to sterilizing time and temperature conditions during their extraction and processing. Soybean oil extraction is accomplished by both a chemical and heating process. Lipids as a class of products are very poor media for microbial growth in that moisture and nutrients are not available for replication.
In the case of rendered animal products, studies have been completed that verifies the animal protein fraction from which the fat is extracted, but still containing six to 10 percent fat, is rendered free of the six most common foodborne microorganisms during the rendering process (Dr. F. Troutt, University of Illinois, “Prevalence of Selected Foodborne Pathogens in Final Rendered Products”). Bacterial cultures and viral isolation attempts from fats, greases, and oils have not been successful (Animal Protein Producers Industry, Annual Microbiological Assay Summaries).
Only recently has bovine spongiform encephalopathy (BSE) been identified in a single cow in Canada and one in an imported cow in the United States. An intensive surveillance program has been in place in both countries since 1986 with the advent of the first BSE diagnosis in the United Kingdom. The 2003 Canadian and U.S. incidences is documentation that the surveillance and compliance programs are effective in preventing an epidemic of BSE in North America. All forward and backward surveillance data acquired to date all provide continuing support to the Canadian incident being of a single animal spontaneous origin. The investigation into the U.S. case is still ongoing.
The U.S. Food and Drug Administration (FDA) has imposed a regulation (21CFR§589.2000) that prohibits ruminant derived tissues from being included in the diet of ruminant animals as a precaution for BSE. Canada has a similar program in place.
Several tissues have been excluded as exempt from those regulations. Tallow, the fat derived from cattle, is an exempt tissue. The common accepted causative agent prion of the transmissible spongiform encephalopathy (TSE) of which BSE is included has never been isolated from fat tissue and oral inoculation studies have not demonstrated the transmission of BSE via tallow. In studies conducted at the Institute for Moekulare Biotechnology in Jena, Germany, by Thomas Appel et. al., and published in the European Journal of Lipid Science and Technology, reported on the safety of oleochemical products derived from beef tallow or bone fat regarding prions. To experimentally prove the destruction of the pathogenic prion protein, aggregate processes were emulated in the laboratory. Fat samples were spiked with highly infectious ex vivo prion rods. Chemical degradation processes of hydrogenation of double bonds, catalytic transesterification, and peptide bond hydrolysis resulted in risk factors for human consumption or skin application exposures as being lower than the background risk of contacting sporadic Creutzfeldt-Jakob Disease (CJD), which has been established at 1 x 106 per annum.
In additional studies conducted at the University College Dublin, “Human Risks from the Combustion of Specific Risk Material (SRM) – Derived Tallow” was published in Human and Ecological Risk Assessment: Vol. 8, No. 5, pp 1177-1192 (2002). As previously referenced, epidemiological studies have failed to incriminate the dietary use of tallow with any risk of BSE development (Wilesmith et. al., 1988, Veterinary Record 123: 638-644). This study, however, addressed the risks to humans associated with the combustion of tallow.
SRMs comprise those parts of an animal that present the greatest risk of BSE infectivity. SRM materials were modeled for worst-case infectious doses with an assumption that insoluble solids, including protein material, may remain in the tallow. The analysis of the risks associated with the combustion of tallow derived from SRMs concluded that the risks are negligibly small. The risks are a number of orders of magnitude less than the sporadic incidence of CJD. Based on current knowledge, there are negligible implications to human health on the use of tallow as a fuel extender or for the manufacture of an alternative fuel.
In high endemic countries with BSE such as the United Kingdom and Germany, tallow and yellow grease methyl esters are a primary utilization for the rendered fat. Thus there is considerable demonstrative evidence that BSE or any of the other TSEs do not present any zoonotic risks when fats, greases, and oils are used as biofuels.
Additionally, as previously referenced, the initial processing of fats, greases, and oils are accompanied with microbial inactivation procedures. The basic manufacturing process of biodiesel exerts additional antimicrobial properties. Both methanol and the acid or base catalysts used in the production process are such compounds. Alcohol has long been used as topical disinfectants. The data available provides assurance that any transmission of disease from any feedstock used for the production of biodiesel or directly as a biofuel would be extremely improbable.
February 2004 Render