Although microbiological contaminants often take center stage in discussions about food safety and quality control in food plants, chemical contaminants and their residues also remain as significant safety and quality issues for food processors. Having stated this, it is appropriate that microbiological hazards in food often get the most attention because they affect a far greater number of people each year than do chemical hazards. As a result, there is always the possibility of overlooking or minimizing the risks associated with chemical hazards. However, a comprehensive food safety program also must consider chemical hazards.
Chemical hazards in food seem to come in cycles, with one surfacing as a concern at a particular time due to factors such as the advent of new scientific information, regional weather conditions affecting crops, agricultural incidents or media and consumer driven issues. The current focus on allergens in food products is one such example. There was not much attention paid to this issue 10 years ago, but because of the severe effects of compounds like peanut protein on sensitive individuals, the regulatory agencies and the food industry are rightly devoting a great deal of resources to reduce cross-contamination of allergenic ingredients. The U.S. Food and Drug Administration’s (FDA) efforts have involved auditing plants to monitor the response of industry and greater scrutiny of food labels. This attention has created an opportunity for manufacturers of kits for allergen detection to expand the number of allergens that can be analyzed. This type of focus on a particular chemical hazard, then, has created more tools for the food industry to assess their plants and prevent cross-contamination.
There are three primary sources of chemical contaminants in a food plant of which food processors should be aware when planning the elements of their food safety program: chemicals that enter the plant with the raw materials or ingredients; chemicals used in the plant to support manufacturing processes; and chemicals used for sanitation purposes. Examples of these chemical hazards include cleaning and sanitizer agents, pesticide residues, hydraulic fluids, lubricants, solvents, allergenic proteins, paint and caustic compounds, mycotoxins and antibiotics. Chemical hazards accounted for 54.60/0 of all recalls reported by FDA in the U.S. in 2001. Since 1990, however, no foodborne illness outbreaks were reported in the U.S. by chemicals used in manufacturing or processing foods.
There have been recalls associated with some of these chemical contaminants. Figure 1 provides a summary of all FDA recalls in 2001, which includes the percentage of recalls issued due to the contamination of foods (including dietary supplements, classified by FDA as foods) by undeclared Generally Recognized As Safe (GRAS) chemicals and non-GRAS chemicals. In addition, the recall data identifies the proportion of recalls due to pesticides, allergens, and so on. It is interesting to note that a review of FDA Enforcement Reports from 1990 to 2002 reveals only four recalls issued by food manufacturers due to the contamination of foods or beverages by machine lubricants. In these cases, compressed air system, gear and conveyor belt lubricants were found to have contaminated the products.
Each of the three primary categories of potentially hazardous chemical contaminants can be addressed and controlled within the framework of a food company’s Hazard Analysis & Critical Control Points (HACCP) plan or chemical control plan. Many of these plans probably are dominated by procedures to prevent microbial hazards at present. Balancing the approach to successfully identify, prevent and control chemical hazards, as well as in the processing operation, will provide added assurance that the safety, quality and wholesomeness of the finished products is maintained.
Identifying Hazards at the Start
There are a variety of chemical contaminants that can enter a food plant via the raw materials or ingredients used to manufacture foods. These hazards range from pesticides found on fruits and vegetables, to growth regulators found in meat or poultry, to mycotoxins that enter with incoming grains. One has to include processing aids and ingredients that can be added in improper amounts to create a hazard. These types of undesirable chemicals also might include residues of agricultural-type chemicals, ingredients like hydrogen peroxide used on some ingredients to promote whitening, and even packaging materials or components. This category of chemical hazards deserves the greatest attention from the food industry because it most likely poses the most risk to consumers. The global nature of the food supply today requires a comprehensive food safety program, as illustrated by the 1999 incident in Belgium in which animal feed was contaminated with dioxin. By the time the problem was discovered, food products contaminated with dioxin, like butter, cheese, pork, beef and chicken were already available for purchase in grocery stores around the world.
Of these chemical contaminants, mycotoxins stand out as a hazard that must be monitored carefully and continuously. This class of toxin produces both acute and chronic toxic effects, and includes some highly carcinogenic compounds such as aflatoxins. Mycotoxin contamination of crops surfaces and fades as a potential problem because their presence at concentrations of concern is often weather-related. This is due to the fact that the molds that produce these toxins proliferate on crops that are stressed by drought or insect infestation, or if the commodity is stored improperly, such as under high-humidity conditions. With ingredients that may be imported from a distant part of the world, this historical information may not be known, making regular monitoring essential.
While there are a number of types of mycotoxins, they tend to be associated with certain crops (patulin and apples, for example). This often limits the scope of testing one needs to perform. Regulatory limits exist for a few of the many known classes of mycotoxins. For example, aflatoxin FDA action levels of 20 parts per billion (ppb) are in place for food destined for human consumption with the exception of milk, where the action limit is 0.5 ppb for aflatoxin M1. deoxynivalenol, or vomitoxin, is regulated by an FDA advisory level of 1 part per million (ppm) for finished products destined for human consumption. Both of these mycotoxins have higher tolerances in place for various types of animal feed.
Under this same category of contaminants, the practice of using low levels of antibiotics as a growth promoter in the feed of meat-producing animals currently is receiving a lot of attention. In fact, it appears that we will see some litigation between the federal government and antibiotic manufacturers regarding the use of growth-enhancing antibiotics in cattle in the near future. Screening for the presence of antibiotics in meat products and milk must be conducted to ensure violative levels of these compounds are not present in these foods. In addition, chloramphenicol recently was detected in honey imported from China, so the presence of antibiotics can be unexpected if one is not familiar with the agricultural practices of other countries. The growing concern of a number of scientists regarding the practice of using antibiotics routinely as a growth promoter is that it will lead to the creation of new pathogens that are resistant to a variety of antibiotics used in treating human infections. Preliminary reports of this occurring are beginning to surface.
Pesticides have been a concern for consumers for a long time because of the publicity they have received through the years. Partly due to the longevity of this issue, the monitoring system for the presence of pesticides in domestically produced food is well established. The FDA market basket survey of 1998 demonstrated that the rate of violative levels of pesticides is less than 1% of the foods surveyed, and less than 3% of the imported products. This does not mean that a company should not be vigilant when monitoring raw ingredients for specific classes of pesticides. As the recent discovery in Japan of high levels of chlorpyrifos in spinach imported from China reminds us, mistakes in the application of pesticides in agriculture sometimes do occur. Because of increasingly global nature of food production, incidents of pesticide contamination of a raw commodity can result in high levels of that pesticide in a finished food product on the other side of the world.
Processing aids, food additives and other chemicals used in food production have been thoroughly tested for safety and have less toxic potential than the chemicals mentioned above. A basic rule of toxicology is that every chemical is toxic in high enough concentrations, and it is the concentration that separates a poison from a remedy. Vitamin D is a good example of a beneficial nutrient that quickly becomes toxic as the concentration increases. For this reason, the HACCP plan of a food plant must include strict controls to ensure the proper amounts of additives and processing aids are added. Regular training of personnel and clear documentation of what was added with each batch of product must be maintained.
A well thought-out HACCP program that addresses chemical contaminants is the best strategy for minimizing the presence of these hazards. Depending upon the nature of the chemical, it could be addressed at one or multiple control points in the processing of food. The key is to focus on potential chemical hazards that could be present in the commodity in question. The suppliers of ingredients should be enlisted to assist in the minimization of chemical hazards entering the food plant at point of raw material/ingredient receipt. This process should begin when a supplier is selected. An audit of the supplier’s facility and review of their HACCP plan may be in order. In addition, the supplier may be required to supply a certificate of analysis (COA) from an independent laboratory with each lot of ingredient certif4ng that the product meets a required specification or regulatory limit.
A second control point is when the ingredient or commodity is delivered. Through the years, our laboratory has been encountered many situations in which product has picked up an off-aroma because it was shipped together with an incompatible chemical or food. The shipping vehicle must be inspected prior to the product being unloaded to verif5r that no unidentified chemicals or extraneous odors are present.
There also have been quite a few detection and control technologies that have emerged that can aid processors in identifying or controlling these types of chemical contaminants as part of their food safety and quality assurance programs. Enzyme-linked immunosorbant assay (ELISA) kits can be developed for any analyte that an animal can produce an antibody against. This technology has been essential to the development of kits for quantitating the presence of large molecular weight compounds that would be otherwise very difficult to analyze. A good example is a kit recently developed to quantitate the level of glial fibrillary acidic protein (GFAP) in meat products. This protein is unique to central nervous system (CNS) tissue. The concern in the meat industry is that advanced meat recovery (AMR) systems that strip meat from back and neck bones also will recover spinal cord material. (See “Advanced Meat Recovery Advances”) If the animal was infected with bovine spongiform encephalopathy (BSE), the CNS material could contain the prion protein responsible for this disease resulting in what is likely the human variant, Creutzfeldt-Jakob Disease.
ELISA kits have also been developed for quantitating growth hormones, antibiotics, vitamins, mycotoxins, other microbial toxins and genetically modified foods. The kits often are easy to use, and usually can be performed with a minimum of laboratory equipment. Using this same technology, lateral flow strip (dipstick) technology has even been produced for safe and easy use in a processing plant or even in a field environment.
Use of a fully equipped laboratory opens up many more analytical techniques that can be brought to bear on the screening for chemical hazards. If the analytes are volatile, like many pesticides, it is possible to screen for a wide variety of these compounds in a single gas chromatographic (GC) analysis. Some pesticide screens can effectively recover and quantitate approximately 75 of these compounds. The pesticides of interest must share certain chemical characteristics, such as the presence of a halogen in order to employ an electron capture detector. The evolution of the mass spectroscopy (MS) as a more sensitive and rugged gas chromatographic detector has been an important development. The capability of this detector to distinguish compounds of very similar structure is critical for the analysis of toxins like PCBs and dioxin. MS is also evolving into a more practical liquid chromatographic (LC) detector, and is finding good use as the detector for quantitating acrylamide in foods. The controversy over the relevance and toxic implications of this latter chemical produced in the preparation of French fries, cereals and baked products is now raging.
Genetically modified foods offer the potential to reduce pesticide usage, produce crops that are more resistant to environmental factors and increase the nutritional benefits of a food. Despite the controversy over genetically modified organisms (GMOs), this technology will be with us for a long time because of this potential. Australia, New Zealand, European Union countries, Japan and others have already placed labeling regulations on foods containing above a stated percentage of GMOs. To participate in the global food market, food companies will have to monitor the GMO content of their ingredients and test the finished product to ensure a shipment is not rejected at a foreign port. As indicated, ELISA kits can test for novel proteins produced by the transgenic event. Our laboratory has chosen to provide testing for GMOs using polymerase chain reaction (PCR) technology. PCR involves the selective amplification of transgenic DNA. The detection method used is known as realtime PCR, and utilizes fluorescent probes that anneal to the DNA in order to quantitate the number of molecules amplified. This technology monitors the number of molecules produced at each stage of the amplification.
Does a Well-Oiled Machine Spell Trouble?
The second type of chemicals that may contaminate food products in the plant environment are those that are used to support manufacturing. This class of chemicals includes machinery lubricants, hydraulic fluid, solvents and many chemicals routinely used by the plant’s maintenance staff. From a food testing laboratory viewpoint, we encounter fewer instances of potential solvent or hydraulic fluid contamination than we did in the past, so it appears food plants have recognized this as a serious source of contamination and have made strides to eliminate it through HACCP plans and other strategies. On some occasions, consumers have detected lipid oxidation in a food and thought that the product was contaminated with a solvent. This is understandable, as some individuals describe lipid oxidation as a “painty” aroma. Actual solvent contamination of food products most often has been associated with the migration of solvents from the packaging material.
One source of chemical contamination under this category that continues to regularly occur is the exposure of food products to ammonia from refrigeration units. Usually, this seems to happen most often in cold storage facilities. We have discovered that ammonia gas has the ability to efficiently penetrate many different kinds of containers. Because ammonia is mainly a lung irritant and does not have other significant toxic effects when encountered as a residue in food, it is not a great concern. It can, however, cause change in the color, flavor and aroma of foods.
There have been a number of occasions in our experience in which lubricants from machinery has wound up in finished food products. Usually, their presence has resulted in an agglomeration of the lubricant, product and other particles in the plant to create a unique-looking object. We have had consumers mistake these agglomerations for rodent body parts and other interesting interpretations. Upon dissection and analysis, it becomes pretty clear what occurred.
The use and storage of these hazardous chemicals must be a part of the chemical hazard control plan. These reagents must be contained in sealed, rugged containers and must be stored away from any food ingredients in locked cabinets and only available to limited personnel. Their use must be restricted to those individuals who have received the proper training to handle these chemicals. With regard to available detection or control technologies for use in the food safety and QC programs, the greatest control tool is most likely the power of observation. As a part of any safety audit, a review of the application and storage of these chemicals should be conducted.
Clean-Up Chemicals
Chemicals that are used for cleaning and sanitation purposes—sanitizers, disinfectants, cleaning solvents—are essential for maintaining a hygienic food processing operation. But these chemicals can cause the food safety professional or quality assurance/quality control team problems, as well. One significant problem is that residual sanitizers or disinfectants can produce an acute toxic effect, such as a burning sensation, if the concentration of the active agent in the food is high enough. These chemicals tend to be either strong acids or bases. We have been involved in some situations in which a consumer has felt that a beverage they tasted was produced by an inadequately rinsed piece of equipment. Due to the chemical nature of these solutions, a pH reading becomes a very effective screening tool when comparing the suspect product versus a control.
It should be remembered that these consumer complaint samples often are temperature abused by the time they are shipped between various parties, and thus have sometimes fermented. Most restaurants or food plants are willing to share the identity of the sanitizers and disinfectants and even provide material safety data sheets for these solutions. From this information one can decide if the chemical in question will shift the pH of the suspect sample up or down. Some sanitizers are chlorine-based. Chloride salts are formed from the reaction of the chlorine with the organic matter in the food product, and thus the chloride concentration of the suspect sample versus control can be compared. Some of these chemicals contain a unique mineral like aluminum, and again, the concentration of this mineral in the suspect sample and a control can be determined.
To manage and control problems with sanitation chemical residues, a food production facility should have a Sanitation Standard Operating Procedure (SSOP) to document the procedure for cleaning and sanitizing each piece of equipment. While the creation of the documentation is important, the training to these procedures is the most critical element. Again, to ensure continued compliance, auditing of this element of the chemical safety program is crucial.
There are a variety of sampling and detection test kits available to food companies to verify that environmental hygiene efforts have been effective. Some are designed to ensure that sanitizer residues do not remain on food contact surfaces following cleaning and sanitizing. ATP bioluminescence, ELISA, swabs and sponge systems, and film technologies are all well- established tools in this effort. The development of control technologies, such as automated sanitizer dispensing systems that eliminate the overuse or misuse of sanitation chemicals through automation and the development of more environmentally friendly sanitizers are also proving helpful in addressing this issue.
Keeping the Balance
In the last few years, outbreaks of microbiological-based food poisoning occasionally have made headlines and held the attention of the nation for a time. A similar chemically-based outbreak has not occurred in the U.S., but the potential is always there. A balanced HACCP plan is essential to keep either type of disaster from occurring. The food industry has made good progress in controlling the presence of hazardous chemicals with which we have been concerned for the last few decades—pesticides, aflatoxins, antibiotics, solvents and sanitizers, to name a few. Much of this progress can be attributed to the implementation of well-designed HACCP programs in a large number of food production facilities.
The challenge for all of us is to keep up with the changing nature of chemical hazards. New procedures must be put into place to eliminate cross-contamination of allergenic proteins to other products. New methods must be implemented to ensure meat products derived from AMR systems are free from CNS tissue. These examples illustrate the fact that we must continue to apply HACCP principles to new challenges that arise.
Dr. Bill Ikins is Corporate Director of Chemistry of Silliker, Inc., and has been a member of the Silliker organization for more than 13 years. A leading authority on food analysis and food safety he has extensive experience with a broad range of food analytical issues. Ikins can be reached at info@silliker.com.
Advanced Meat Recovery Advances
With the U.S. Department of Agriculture’s (USDA) June announcement of new measures to ensure that meat products derived from Advanced Meat Recovery (AMR) systems are accurately labeled for consumers, the beef industry is increasingly concerned with the food safety and human health risks posed by product contamination with central nervous system tissue (CNST) due to slaughter or processing practices. University of California-Davis (UCD) researchers are leading the way in studying some of the available detection methods that will help the meat industry comply with the new government policies.
AMR is a technology that enables processors to remove remaining muscle tissue from beef carcasses without breaking bones. Currently, FSIS inspectors are authorized to take regulatory samples of AMR product if they believe that an establishment is not completely removing spinal cord tissue. Spinal cord tissue is not allowed in meat prepared via AMR systems and the new sampling program will require inspectors to test AMR product on a routine basis to verify that spinal cord tissue is not present.
“Although there have been no cases of BSE in the U.S., UCD has been working on projects to address the sampling and testing methods for the detection of spinal cord tissue in meat, particularly ground beef,” says Maha Hajmeer, Ph.D., with the Department of Population Health & Reproduction at the UCD School of Veterinary Medicine. “There are more and more concerns associated with BSE because of possible transmission to humans. With the new USDA FSIS policy, the detection method efficacy becomes very important’
Hajmeer, along with UCD’s Dean O. Cliver, Ph.D., and others, recently released results of a comparison study of two commercially available immunological methods used to detect spinal cord (SC) tissue in comminuted beef, The test kits—R-biopharm Ridascreen” Risk Material 10/5 and ScheBo” Brainostic Test— were compared for the detection of central nervous system tissue, considering sensitivity, specificity, cost and time factors. The Brainostic test is based on the immunological detection of a CNS-specific antigen, neuron-specific enolase (NSE), while the semi-quanitative Ridascreen Risk Material test is based on an enzyme immunoassay for a cellular marker restricted to CNS called the glial fibrillary acidic protein (GFAP).
Using three quality grades of meat—choice, select and utility—the samples were ground and divided into batches. Minced spinal cord was mixed with meat to yield 0.0, 0.025, 0.05, 0.1, 0.2, 0.4, 0.8, and 1.6% SC in meat. Each batch was homogenized and divided into two equal portions; one was sampled following 30 minutes of refrigeration, and the other frozen for 24 hours, thawed, and sampled. Five replicates per SC concentration were performed per each manufacturer’s recommendations.
According to the study, both the Brainostic and Ridascreen kits detected SC at claimed levels; 0.25% and 0.11%, respectively. The Ridascreen assay detected SC at 0.025%; a level lower than its claimed 0.11% designed for brain and SC combined, which the researches note, renders the Ridascreen test approximately 10 times more sensitive than the Brainostic. The study also showed that meat quality grade had no influence on SC detection of either fresh or frozen meat.
“Essentially, we found that SC in uncooked meat can be detected by both kits,” says Hajmeer, “and both kits can be an alternative to pathological examination. Future research should focus on the detection of CNST overtime, the effect of fat level in a meat system, and the detection of CNST in cooked meats.”
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