Food contamination is the presence of any unwanted substance. Contaminants can range in severity:
- from simply causing food to be un appealing or un-wholesome such as finding a hair or insect fragment in one’s soup
- to dangerous causing acute or chronic and or debilitating illness such as contamination with certain toxins
- to life threatening, such as can be the case with food allergens.
In food chemistry and medicinal chemistry, the term “contamination” is used to describe harmful intrusions, such as the presence of toxins or pathogens in food or pharmaceutical drugs, food contaminant. Unfortunately, there is no single ‘one stop’ test for contaminants, rather, contaminant testing methods are specific to the target contaminant and draw on virtually every testing technology in the food chemists tool box; from simple physical observation, separation and microscopic observation, through solvent extractions, Enzyme Linked Immunosorbent Assays (ELISA), to the most advanced Mass Spectrometer Chromatography methods.
Because contaminant testing is so diverse, and potentially expensive, testing for all contaminants in all food would be highly impractical if not impossible. Yet, as mentioned, contaminants can pose serious even life-threatening risks in specific instances. For this reason, food safety concerns dictate that foodstuffs and ingredients be analyzed from a comprehensive risk based “Hazard Analysis” perspective which constructs a matrix considering the likelihood of a specific contaminant, as well as its potential severity, for each item.
Factors for consideration should include:
- Contaminants historically associated with a particular commodity such as mycotoxin infection, or insect infestation in cereal grainso Specific seasonal or regional factors such as incidence of crop stress from drought or flooding etc.
- Whether there may be risks of cross-contamination from shared harvesting, transporting, or processing equipment, as with allergens.
- Geographic origin of commodities concerns, such as the likelihood of heavy metals or radiation contamination from the soil, or water of a particular region.
- Pesticides commonly associated with the production of a region and/or a given commodity.
- Economic motivation for food fraud such as dilution or substitution of high cost commodities with less expensive ingredients, like: adding corn syrup to honey, or substituting lower grades of olive oil for ‘Extra Virgin’ grade.
- Length and complexity of the supply chain for a given commodity impacting the ease of access to commodities and the probability of economic fraud or culturally motivated poisoning.
- History, and audit frequency of a given supplier.
The most commonly considered classes of contaminants include, but are not necessarily limited to the following:
Heavy Metals: There is No good definition of “Heavy Metals”. A metallurgist would consider Heavy Metals based on their density while a Physicist would be concerned with the atomic number. From the perspective of food chemistry, we consider Heavy Metals to be toxic elements. Mercury, Lead, Cadmium, and Arsenic are the most commonly tested for heavy metals.
Challenges with Heavy Metals
Toxic elements are present in almost all samples by modern methods, with detection limits in the ppb range. For this reason, tolerance thresholds need to be based on epidemiologic evidence, not a simple binary detect / non-detect standard. Heavy metals are often naturally occurring. For example:
- Arsenic in rice.
- Toxicity varies greatly based on form or “species”.
- Inorganic arsenic.
- Methyl mercury.
- Chromium +3 and Chromium +6
Mycotoxins: Are produced by molds of the Aspergillus, Fusarium and Penicillium genera. Their production is determined by environmental factors such as temperature, humidity, pest attack and plant stress during the growing season and subsequent storage of grains.
There are over 300 mycotoxins, however the main classes which are of significance to human health are:
- Aflatoxins (B1, B2, G1 and G2). Aflatoxin M1 & M2 come from milk produced by dairy animals after ingesting feeds contaminated with aflatoxins B1 & B2.
- Ochratoxins – ochratoxin A (OTA).
- Trichothecenes – deoxynivalenol (DON) T2, and HT-2.
- Fumonisins (FB1, FB2, FB3).
- Patulin – a mycotoxin associated with apples and apple products from bruised or damaged apples.
- Zearalenone (ZEA).
The toxic properties of mycotoxins are serious and numerous, they include:
Analysis methods for mycotoxins is typically accomplished by rapid screening methods such as thin layer chromatography, ELISA, and/or fluorescence polarization immunoassay (FIPA).Confirmatory testing of positive samples is most often done with HPLC methods after and Immuno-Affinity Column cleanup of the sample.
Obtaining a representative and repeatable sample is the biggest single challenge with mycotoxin testing, as the infection occurs within individual grain kernels, and 1 single infected kernel of grain can contain enough toxin to contaminate up to 10 lbs. of product.
Pesticides:The term pesticide includes all of the following: herbicide, insecticide, insect growth regulator, nematicide, termiticide, molluscicide, piscicide, avicide, rodenticide, predacide, bactericide, insect repellent, animal repellent, antimicrobial, fungicide, disinfectant (antimicrobial), and sanitizer.
A chemical preparation for destroying plant, fungal, or animal pests
A pest is an insect or other organism harmful to cultivated plants or to animals. Pesticides may be classified on the basis of target organisms and chemical composition.
- N-methyl carbamates
- Phenoxy acids.
Antibiotics and or Veterinary Drug Residues: Animals for the production of meat, milk and eggs intended for human consumption are often treated with a variety of anti-biotics, anti-fungal agents, and anti-inflammatory drugs. Additionally, some countries allow the use of drugs including sub-clinical levels of antibiotics, hormones and beta-adrenoreceptor agonists such as ractopamine, as growth promoters.
There are regulated withdrawal periods specifying the time between the last administration of the drug and slaughter or collection of milk or eggs, however antibiotic and Veterinary Drug residues are a concern for human food.
An allergen is a substance (antigen) that stimulates the immune system in an inordinately strong response. In most cases the antigen would be harmless to the organism. Examples of allergens include:
- Insect stings/bites
- Pet dander
- Mold spores
- Food allergens.
According the Mayo Foundation for Medical Education and Research (2018), “a food allergy is an immune system reaction that occurs soon after eating a certain food. Even a tiny amount of the allergy-causing food can trigger signs and symptoms such as digestive problems, hives or swollen airways.”
The Food Allergen Labeling and Consumer Protection Act has identified eight foods or food groups as the major food allergens. They are:
- Fish (e.g., bass, flounder, cod)
- Crustacean shellfish (e.g., crab, lobster, shrimp)
- Tree nuts (e.g., almonds, walnuts, pecans)
Genetically modified organisms are a relatively new class of contaminant. GMO’s are created by the insertion of a section of DNA (transgene) from a separate organism. Often to impart a specific resistance to pests or herbicides and/or environmental stress, or to improve quality.
The most common GMO crops include: corn, soybeans, cotton, canola, rice, sugar beets and papaya. The most common detection method is real time polymerase chain reaction (PCR) amplification and detection of the transgene base sequence. Contaminants testing is a broad and diverse category of food chemistry involving nearly every available technology. Because contaminants testing can be very time consuming and expensive, a comprehensive risk assessment for each commodity is needed to assure that testing resources are being managed in an effective and efficient way.
The types and classes of potential contaminants vary with each commodity and potentially each supplier. Factors such as region and season of production, length and complexity of the supply chain, and supplier history should be considered.