Chemical Food Contaminants

Food Contaminants

Food contamination refers to the presence in food of harmful chemicals and microorganisms which can cause consumer illness where chemical food contamination is mostly attached with toxicity or carcinogenic reactions while microbes are well known for fatal and nonfatal diseases.  The impact of chemical contaminants on consumer health and well-being is often apparent only after many years of processing prolonged exposure at low levels (e.g., cancer). Chemical contaminants present in foods are often unaffected by thermal processing (unlike most microbiological agents). Chemical contaminants can be classified according to the source of contamination and the mechanism by which they enter the food product. There are number of chemical food contaminants identified and tested and regulated for the wellbeing of human race. These chemical come under following categories:

Dioxins

Polychlorinated biphenyls (PCBs)

Food allergens

Heavy metals

Melamine

Mycotoxins

Pesticides

Radiation contamination

Veterinary drug residues

Dioxins

Dioxins are a class of chemical contaminants and it is also called as persistent organic pollutants (POPs), meaning they take a long time to break down once they are in the environment. Dioxin is a general name for a large group of chemical compounds with similar structure. These compounds are made up of carbon, oxygen, hydrogen and chlorine atoms. The number of the chlorine atoms and their positions in the dioxin molecule are what determines the toxicity of different dioxins. The most toxic dioxin has four chlorine atoms in positions 2, 3, 7 and 8. This dioxin ( 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin) is often referred to as TCDD or “dioxin”. TCDD is the most studied and the most toxic of the dioxins.

Dioxins are formed during combustion processes such as waste incineration, forest fires, and backyard trash burning, as well as during some industrial processes such as paper pulp bleaching and herbicide manufacturing. Dioxins are highly toxic and can cause cancer, reproductive and developmental problems, damage to the immune system, and can interfere with hormones. The most toxic chemical in the class is 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD). Dioxins are found throughout the world in the environment and they accumulate in the food chain, mainly in the fatty tissue of animals and more than 90% of human exposure is through food, mainly meat and dairy products, fish and shellfish. The highest environmental concentrations of dioxin are usually found in soil and sediment, with much lower levels found in air and water.

Dioxins, Furans, PCBs

Dioxins, furans, and polychlorinated biphenyls (PCBs) (All contain phenyl rings of carbon atoms) are a class of similar chlorinated aromatic organic compounds, where Dioxins have two phenyl rings connected by two oxygen atoms. On contrary, Furans have one or two phenyl rings connected to a furan ring and PCBs have two phenyl rings attached at one point. One or more chlorine atoms can attach to any available carbon atom, allowing for 100 - 200 forms of each. Dioxins and dioxin-like furans have no known commercial or natural use. They are produced primarily during the incineration or burning of waste; the bleaching processes used in pulp and paper mills; and the chemical syntheses of trichlorophenoxyacetic acid, hexachlorophene, vinyl chloride, trichlorophenol, and pentachlorophenol. PCBs were once synthesized for use as heat-exchanger, transformer, and hydraulic fluids, and also used as additives to paints, oils, window caulking, and floor tiles. Production of PCBs peaked in the early 1970s and was banned in the United States after 1979.

Exposure

Human exposure to PCDDs, PCDFs, and PCBs may occur through background (environmental) exposure, and accidental and occupational contamination. Over 90 percent of human background exposure is estimated to occur through the diet, with food from animal origin being the predominant source. PCDD and PCDF contamination of food is primarily caused by deposition of emissions from various sources (e.g. waste incineration, production of chemicals) on farmland and water bodies followed by bioaccumulation up terrestrial and aquatic food chains. Other sources may include contaminated feed for cattle, chicken and farmed fish, improper application of sewage sludge, flooding of pastures, waste effluents and certain types of food processing. If the dioxin-like PCBs (non-ortho and mono-ortho PCBs) are also considered, the daily TEQ intake can be a factor of 2-3 higher. Special consumption habits, particularly one low in animal fat or consumption of highly contaminated food stuffs may lead to lower or higher TEQ intake values, respectively. Compared to adults, the daily intake of PCDDs/PCDFs and PCBs for breast fed babies is still 1-2 orders of magnitude higher on a per body weight basis. The latest WHO field study showed differences between the PCDD/PCDF and PCB contamination of breast milk, with higher mean levels in industrialized areas (10-35 pg I-TEQ/g milk fat) and lower mean levels in developing countries (< 10 pg I-TEQ/g milk fat).

High exposure may also be caused by food items accidentally contaminated. Known examples are the contamination of edible oil, such as the Yusho (Japan) and YuCheng (Taiwan) food poisoning. For a group of Yusho patients, average intake by ingestion of the Kanemi rice oil contaminated with PCBs, PCDFs and polychlorinated quarterphenyls (PCQs) was estimated at 154000 pg I-TEQ/kg bw/day, which is five orders of magnitude higher than the reported average background intake in several countries.

Mechanism of Action

A broad variety of data primarily on TCDD but also on other members of the class of dioxin-like compounds has shown the importance of the Ah (dioxin) receptor in mediating the biological effects of dioxin where data have been collected in many experimental models in multiple species including humans. The precise chain of molecular events by which the ligand-activated receptor elicits these effects is not yet fully understood. However, alterations in key biochemical and cellular functions are expected to form the basis for dioxin toxicity.

Effects of Dioxins on Human Health

Short-term exposure of humans to high levels of dioxins may result in skin lesions, such as chloracne and patchy darkening of the skin, and altered liver function. Long-term exposure is linked to impairment of the immune system, the developing nervous system, the endocrine system and reproductive functions. Chronic exposure of animals to dioxins has resulted in several types of cancer. The developing fetus is most sensitive to dioxin exposure. Newborn, with rapidly developing organ systems, may also be more vulnerable to certain effects. Some people or groups of people may be exposed to higher levels of dioxins because of their diet (e.g., high consumers of fish in certain parts of the world) or their occupation (e.g., workers in the pulp and paper industry, in incineration plants and at hazardous waste sites).

Prevention and Control of Dioxin Exposure

Proper incineration of contaminated material is the best available method of preventing and controlling exposure to dioxins. It can also destroy PCB-based waste oils. The incineration process requires high temperatures, over 850°C. For the destruction of large amounts of contaminated material, even higher temperatures - 1000°C or more - are required. Trimming fat from meat and consuming low fat dairy products may decrease the exposure to dioxin compounds. Also, a balanced diet (including adequate amounts of fruits, vegetables and cereals) will help to avoid excessive exposure from a single source. This is a long-term strategy to reduce body burdens and is probably most relevant for girls and young women to reduce exposure of the developing fetus and when breastfeeding infants later on in life. However, the possibility for consumers to reduce their own exposure is somewhat limited.

Reference:  

http://www.who.int/mediacentre/factsheets/fs225/en/

http://www.who.int/ipcs/publications/en/exe-sum-final.pdf

http://unsolvedmysteries.oregonstate.edu/flow_02

http://www.greenfacts.org/en/dioxins/l-2/dioxins-1.htm

Revolution of Food Quality and Food safety Testing Instruments

The Global Testing Instrument Market

The global food quality and safety testing industry is a diverse market comprising of various equipment and consumables where there are various food types that are tested globally for attributing not just quality or safety but also for the nutritional value of food being consumed. The market is segmented into different equipment types and consumable type, by food type, by contaminants and by geography. According to the IndustryARC (2015), the Global Food Safety Testing Equipment Market alone for 2015 would be around $2,320.6 Million and that of Consumables around $2,142.3 Million. On the other hand, the report further stress that, the global food testing market which also includes the food safety testing market is expected to grow at a healthy growth rate of around 6% during the forecast period of 2013 – 2018 to reach $4.63 Billion in 2018 from $3.45 Billion in 2013.

However, there are no proper quantifiable data available on the local food testing market statistics which can be expected to grow due to the globalization, modern trends in the local market and the awareness created on food safety and quality among general public. In addition to that, export market is totally driven by quality and safety where food industry’s future is more focused on food safety, quality and traceability initiatives. As to the global food testing initiatives which are mostly intensified due to rise in global trade, increase in food mishaps resulting in product recalls, growing consumer awareness on food safety, clamor for labeling and increasing trend of outsourced testing, inspection and certification (TIC) activities are the key drivers for increasing demand for food safety testing equipment. The most prominent factor fuelling the market growth is the stringent regulations enforced by regulatory agencies of various countries.

Food safety testing equipments are mostly used for contaminant testing, where those tests are conducted to check for contaminants such as bacteria, fungi, allergens, and GM traces. In 2015, food microbiology dominates the food safety testing equipment market by type of contaminants. This segment is poised to exhibit the fastest growth due to the perishable nature of food as well as being highly prone to contamination. GMO and allergen testing are the other promising segments exhibiting high growth. North America is the dominant region in 2015. Increase in food safety standards in China and India is driving the demand for food safety testing equipment and consumables in APAC.

Food safety testing equipment has been segmented based on their technology into key types such as mass spectrometers, chromatography, PCR, ELISA, Immunoassay, NMR Spectroscopy, flow cytometry, hybrid-systems and others. PCR equipment is the dominant device type in 2014 and is estimated to exhibit the fastest growth through 2020 due to increasing installations. Immunoassay and Hybrid systems are also poised to exhibit faster growth as these are rapid analytical systems that hold huge potential for growth. 

Categorization of Testing Equipments and Devices  

The food safety testing was considered as the focus of the Life Science Division where products can be differentiated according to the following methods.

Food Safety Equipment and Devices (by Technology)

Chromatography

Mass spectroscopy

Polymerase Chain Reaction (PCR)

Hybrid

ELISA

Immunoassay

Flow Cytometry

Others

Food Safety Equipment and Devices (by Contaminants)

Pathogens

Toxins

Pesticides

GMO

Others

Food Safety Equipment and Devices (by food type)

Milk and dairy products

Fruits and vegetables

Meat products

Poultry and Fish products

Cereal & Nuts

Grains

Others

Food Safety Equipment Consumables

Test kits

Reagents

Technology Applications in Food Industry

Chromatography

GC, HPLC, traditional selective detectors, MS, solid-phase extraction (SPE), and liquid-liquid extraction (LLE) are the current leading approaches in analytical food and agricultural applications. These techniques have usurped previous major analytical tools, such as thin-layer chromatography, Soxhlet extractions, tedious wet chemical methods, and non-selective GC detectors. The features and performance of the current leading technologies are established parameters, and any new technique will have to match or better them for a reasonable price.

Gas chromatography (GC) is used widely in applications involving food analysis. Typical applications pertain to the quantitative and/or qualitative analysis of food composition, natural products, food additives, flavor and aroma components, a variety of transformation products, and contaminants, such as pesticides, fumigants, environmental pollutants, natural toxins, veterinary drugs, and packaging materials. On the other hand, chromatography is used for quality control in the food industry, by separating and analyzing additives, vitamins, preservatives, proteins, and amino acids. It can also separate and detect contaminants such as aflatoxin, a cancer-causing chemical produced by a mold on peanuts. Chromatography can be used for purposes as varied as finding drug compounds in urine or other body fluids, to looking for traces of flammable chemicals in burned material from possible arson sites.

Mass Spectrometry

Mass spectrometry (MS) is an analytical technique that measures the molecular masses of individual compounds and atoms precisely by converting them into charged ions. For over 100 years, it has played a pivotal role in a variety of scientific disciplines. With a small beginning in the late nineteenth century as a tool to detect cathode rays, mass spectrometry currently has become an integral part of proteomics and drug development process. Several diverse fields, such as physics, chemistry, medicinal chemistry, pharmaceutical science, geology, nuclear science, archeology, petroleum industry, forensic science, and environmental science, have benefited from this highly sensitive and specific instrumental technique. The Mass Spectrometry is applied in food chemistry fields for the analysis of toxic compounds and contaminants, for nutraceutics and for the characterization of foodstuff to be applied for production areas and traceability. On the other hand, MS is an excellent technology for identifying fraud when the fraudulent action relates to a change of composition of the product, that is, a replacement, blend, or addition. Other technologies may aid this, such as Site-specific Natural Isotope Fractionation (SNIF), a technology that allows the geographic origin of a product to be determined.

Polymerized Chain Reaction (PCR)

PCR is a technique that is used to amplify a single or a few copies of a piece of nucleic acid, to generate thousands to millions of copies of a particular nucleic acid. It allows much easier characterization and comparisons of genetic material from different individuals and organisms. Simply stated, it is a “copying machine for DNA molecules”. PCR represented a revolution in biological techniques when it was first developed in 1983 by Kary Mullis (Saiki et al., 1985). PCR allows the biochemist to mimic the natural DNA replication process of a cell in the test-tube. DNA replication is a biological process in living cells that starts with one double-stranded DNA (dsDNA) molecule and produces two identical (double-stranded) copies of the original dsDNA. Each strand of the original dsDNA serves as a template for the production of the complementary strand. PCR is thus simply the in-vitro replication of dsDNA. PCR is now a common, simple and inexpensive tool that is used in many different areas, from medical and biological research, to veterinary medicine, hospital analyses, forensic sciences, and paternity testing, and in the food and beverage, biotechnology and pharmaceutical industries, among others. PCR is used for different applications, like DNAbased phylogeny, DNA cloning for sequencing, functional analysis of genes, diagnosis of genetic and infectious diseases, human DNA identification, and identification and detection of bacteria and viruses. The principal of PCR is based on thermal cycling, which exploits the thermodynamics of nucleic-acid interactions. The vast majority of PCR machines now use thermal cycling, i.e., alternately heating and cooling of the PCR samples following a defined series of temperature steps. These thermal cycling steps are necessary first to physically separate the two strands in a dsDNA double helix, in the high-temperature process known as DNA melting. At lower temperatures, each strand is then used as a template in dsDNA synthesis, aided by the enzyme DNA polymerase, for the synthesis of the new, complementary, DNA strands.

Conventional methods for the detection of pathogens and other microorganisms are based on culture methods, but these are time consuming and laborious, and are no longer compatible with the needs of quality control and diagnostic laboratories to provide rapid results (Perry et al., 2007). In contrast, PCR is a specific and sensitive alternative that can provide accurate results in about 24 h, and this thus opens a lot of possibilities for the direct detection of microorganisms in a food product. The targets in the foods are DNA or RNA of pathogens, as spoilage microorganisms; DNA of moulds that can produce mycotoxins; DNA of bacteria that can produce toxins; and DNA associated with trace components (e.g. allergens, like nuts) or unwanted components for food authenticity (e.g. cows’ milk in goats’ milk cheese). In recent years, PCR has been increasingly used in other areas, such as food hygiene, food toxicology and food analysis. However, when PCR is applied for detection of pathogens in food products, some problems can be encountered, although many of these can be solved by the use of suitable sample preparation methods (Lantz et al., 1994; Hill, 1996).

ELISA

The enzyme-linked immunosorbent assay ELISA kit is a molecular biology industry standard—a rapid immunochemical test that uses components of the immune system and chemicals to detect potential allergic reactions in the body. Traditional food allergen detection uses ELISA to find protein. This common practice, which uses antibodies to detect antigens, is applied through the preparation of monoclonal antibodies, which detects their presence through the confirmation of an allergen. Every allergen has a specific protein that makes it unique, one that can cause a negative physical reaction when the body doesn’t recognize it. ELISA methods detect the actual allergen protein molecule by binding antibodies to the allergen and then using an enzyme-linked conjugate to create a colorimetric change that can be measured. There are certain instances though, that ELISA methods should not be used. Some matrices can interfere with the ELISA method, such as chocolate, or can cause cross reactivity as seen between different types of nuts. This method is also not the most suitable for cooked or heated products because the protein molecules are denatured or broken down and the allergen is no longer detectable, but may still cause problems to sensitive individuals.

Immunoassay

Immunoassay techniques using the highly specific and sensitive nature of immunological reactions have been developed and applied in the food industry for detecting the naturally occurring constituents, antibiotics, pesticide residues, microorganisms, and fragments of microbial constituents related to food analysis, food production, food processing, and food safety. Both polyclonal and monoclonal antibodies are employed for the development of the various immunoassay systems, including enzyme-linked immunoassay (ELISA) and radioimmunoassay (RIA). Immunoassay techniques provide complementary and/or alternate approaches in reducing the use of costly, sophisticated equipment and analysis time, but still maintaining reliability and improved sensitivity. Immunoassay techniques in their most simple forms provide excellent screening tools to detect adulteration and contaminations qualitatively. The application of immunoassay techniques contributes tremendously to the quality control and safety of global food supply.

Flow Cytometry

Flow Cytometry (FC) is a technique for the rapid analysis of multiple parameters of individual cells. One of the limitations of conventional methods for the analysis of cell populations is the determination of a single value for each cell parameter, which is considered representative of the whole cell population. In contrast, FC aims to obtain segregated data, corresponding to different cell subpopulations. In flow cytometers, single cells or particles pass through a light source in a directed fluid stream, and the interaction of the individual cells with the light source can be recorded and analyzed, using the principles of light scattering, light excitation and the emission from fluorescent stains. Thus, the data obtained can provide useful information on the distribution of specific characteristics in cell populations.

The time required for conventional tests can lead to substantial delays in product release to the market in food and beverage industries, whereas Flow Cytometry (FCM) has been used in conjunction with viability markers for rapid counting of yeast, mold and bacterial cells in food products. A single-parameter flow cytometer has proved applicable to the rapid detection of low numbers of microbial contaminants in finished products. The excellent correlation between FCM results and product quality shelf-life expiry date has allowed the establishment of realistic quality control criteria for rapid positive release of product. Used for the monitoring of microbial biomass during manufacturing processes, flow cytometry allowed a direct assessment of bacterial growth. The reproducibility of the results and the proven correlation with standard plate count method obtained in industrial conditions make FCM a good predictive method for product and process quality control.