When you hear the words “food contamination” your mind makes an immediate connection to unpleasant words such as: illness, disease, unsafe, etc. However, it’s very unlikely that the word “chromatography” comes to mind. One dictionary definition of “contamination” has it as “the action of making something impure by polluting or poisoning.” In other words, the “pure” becomes “impure” by the introduction of something bad that isn’t supposed to be there. Narrowing the definition to the subject of “food contamination,” one definition describes it as “the presence in food of harmful chemicals or microorganisms which can cause consumer illness.” Again something bad has been introduced that shouldn’t be there, that making the wholesome unwholesome. Food contamination is often divided into two categories: chemical and microbiological. This article will deal only with the chemical contamination of food.*
The Chemical Contamination of Food
It is impossible to deal seriously with the subject of the chemical contamination of food without drilling down deeply on such questions such as:
- What is the potential contaminant?
- How much is there?
- Where did it come from?
- How did it get in the food?
- What is the specific danger or health risk?
- How can potential contamination be prevented?
The chemical contamination of food is usually (but not always) quite subtle. Unlike the urgent potato salad incident described in the footnote, the chemical contamination of food is often manifested as trace level exposure to toxic chemicals over long periods of time (i.e., chronic exposure). Potential health effects may not to be realized until many years later, perhaps in the form of carcinogenicity, teratogenicity, and/or metabolic disturbances. And, unlike microbial contamination that can be reversed by such techniques as heating, the chemical contamination of food is generally not reversible. Chemical contamination can only be “cured” by prevention, and prevention is impossible without deep, scientific knowledge about the chemical system associated with the potential for contamination. If you can’t identify, detect, and measure the potential chemical contaminant, you can’t prevent it from happening. You are relying on luck, not science.
The above concept illustrates why the Food Safety and Modernization Act (FSMA) represents such a revolutionary advance in the area of making food safe from chemical contamination. FSMA is wholly anticipatory, not reactionary. You are not allowed to wait decades for a subtle carcinogenic effect to manifest itself before taking action; you must reasonably anticipate the threat of contamination and take proactive measures to prevent it. In other words, you must answer the question number 6, mentioned previously. However, you can’t begin to answer question number 6 without reliably answering questions number 1 and 2. For effective prevention, you need to use analytical testing methods that are both qualitatively and quantitatively reliable. The FDA consistently uses the term “scientifically-valid” to describe this basic requirement. Therefore, if prevention is the heart and soul of FSMA then scientifically-valid food testing methods are the means to effective prevention. However, the term “scientifically-valid method” is not a static definition, but a fluid concept.
Food Testing Method Modernization Movement
As technology has advanced, the ability to identify, detect, and measure chemical substances in environmental samples (such as food) has increased exponentially. Arguably, the advance of analytical testing capabilities in the past two decades has exceeded the advance of the prior 100 years. Consequently, food testing methods that may have been the pinnacle of scientific-validity when they were developed 20 years ago may now be quite dated in terms of analytical capability. This is particularly manifested in the inability of many older test methods to adequately differentiate and quantify specific chemical species. This has increased the risk of chemical contamination, particularly in light of the globalization of food supplies which has complicated the tracking of food ingredient origins.
This probably best illustrated by the unfortunate incident of 2007-2008 where ingredients used in the manufacture of pet food and infant formula were intentionally contaminated (i.e., adulterated) with melamine to fraudulently increase the measured protein content. The scheme initially succeeded because the prescribed test used to measure the protein content (the 100+ year-old Kjeldahl test for total organic nitrogen) can’t distinguish between the nitrogen content of protein and melamine. The Kjeldahl test lacks the ability to speciate specific organic nitrogen compounds and is not fit for the purpose of measuring the protein content of food, at least in the face of a chemical contamination threat from melamine. A sophisticated HPLC test for melamine was subsequently developed, which put an end to that particular contamination threat.
The melamine tragedy brought rapid realization of the vulnerability of many older food testing methods for preventing chemical contamination, whether accidental or intentional. This vulnerability arises from an inherent lack of specificity of older food testing methods—the inability to accurately speciate individual toxic chemical species in a complex food matrix. This inability is particularly stark when one compares the technology underlying the older methods to the much greater capabilities of modern analytical technology. This has led to a broad-based, method modernization effort on the part of government agencies (FDA, NIOSH, EFSA, etc.) and standard setting institutions (AOAC, USP, etc.) to enable ability to measure, and therefore prevent, the chemical contamination of food. Modern chromatography has played a major role in this food method modernization movement and the ability to prevent food contamination.
Impact of Modern Chromatography
In the introduction to this article, I stated that the term “chromatography” probably isn’t the first thing that comes to mind when considering the subject of food contamination. But, perhaps it should be; at least in the case of chemical contamination. Modern chromatography has an unsurpassed ability to isolate, differentiate, and identify diverse potential contaminants in food. There are many diverse opportunities for food to become chemically contaminated. One needs only to consider the great number of toxic compounds in commerce and the many potential exposure routes from farm to table. The potential for contamination is so diverse, it is impossible to generalize the power of chromatography to prevent food contamination. Instead, I will present a series of thumbnail sketches that illustrate the breadth and depth of recent chromatographic method developments.
The following images are all examples taken from the recently published Phenomenex Food Testing Applications Guide that contains over 150 liquid chromatography (LC), gas chromatography (GC) and solid phase extraction (SPE) applications.
Diversity of Potential Chemical Contamination Scenarios
Mycotoxins: Mycotoxins from cereal based goods by SPE and LC/MS/MS. Produced by certain molds that can grow on grains, mycotoxins are a class of compounds that are highly toxic and carcinogenic.
PAHs: Polycyclic aromatic hydrocarbons (PAHs) in water by GC/MS. PAHs are a class of carcinogenic compounds that arise from the inefficient combustion of petroleum-based products and can contaminate the environment and foods.
PFASs: 23 per-polyfluoronated alkyl substances (PFAS) by UHPLC/MS/MS. PFAS compounds have been widely used in food packaging; they are able to leach into food at trace levels, and since they are extremely bioaccumulative, they can build up in the fat tissue of the consumer.
Acrylamide: Acrylamide from coffee by SLE and LC/MS/MS. Acrylamide can be found in certain starch-containing foods that have been exposed to heat. Acrylamide is classified as a carcinogen so its presence in food, even at low concentrations, is a concern.
Pesticides in Spinach: Pesticide residues in spinach by QuEChERS, LC/MS/MS, and GC/MS.
The rapidly evolving science of chromatography has enabled ever more powerful, sophisticated, and effective food testing methods. In turn, these improved methods have greatly strengthened the ability to anticipate and prevent food contamination. Better science-based food testing methods have clearly served to make food safer. And, the science and practice of chromatography is certain to continue its advancement, thereby insuring future improvements in food safety.
Dr. Kennedy, business development manager at Phenomenex, has focused on food safety and environmental monitoring during his over 45-year career. Reach him at Davidk@phenomenex.com.
*Since I am a chemist, and not a microbiologist, I am not qualified to hold a professional opinion on the subject microbial contamination. My only direct experience with the microbiological contamination of food consists of having used my gastrointestinal tract as an indicator of having consumed contaminated potato salad at a family picnic years ago.