Food Safety Magazine, February/March 2013

Testinglin, can cause severe allergic reactions insensitive individuals, which is an importantreason for enforcing their residuelimits in foods of animal origin. Anotherimportant justification for limiting antibioticusage in food-producing animalsis to reduce the risk of pathogenicmicroorganisms becoming resistant toantibiotics. Most veterinary drugs are notof acute toxicological concern, but somesubstances, such as nitrofurans, chloramphenicol,clenbuterol and diethylstilbestrol,have been banned in most countriesdue to their carcinogenicity. Concernabout endocrine-disrupting effects hasbecome another reason for regulationof certain veterinary drugs, such as betaagonistsand hormones.Environmental ContaminantsEnvironmental contaminants canbe man-made or naturally occurringsubstances present in air, water or soil.They can enter the food chain andeven bioaccumulate. Some can posean acute health risk if present at higherconcentrations, but the major concernrelated to the presence of environmentalcontaminants in foods is their potentialendocrine disruption, developmental,carcinogenic and other chronic effects.Examples of environmental contaminantsthat enter the food chain includeheavy metals, polychlorinated biphenyls(PCBs), “dioxins” (polychlorinateddibenzodioxins and dibenzofurans),persistent chlorinated pesticides (e.g.,DDT, aldrin, dieldrin, heptachlor, mirex,chlordane), brominated flame retardants(mainly polybrominated diphenylethers), polyfluorinated compounds,polycyclic aromatic hydrocarbons(PAHs), perchlorate, pharmaceutical andpersonal care products or haloacetic acidsand other water disinfection byproducts.The manufacture and use of PCBsand other persistent organic pollutants(POPs) have been banned for years, butthey remain in the environment due totheir high stability. PAHs can be foundin the environment as a result of industrialpollution or can originate fromoil spills; thus, they were of concern inseafood after the oil spill accident in theGulf of Mexico in 2010.Food Processing ContaminantsCertain toxic or undesirable compoundscan be formed in foods duringtheir processing, such as during heating,baking, roasting, grilling, canning, hydrolysisor fermentation. Precursors of thesecontaminants can occur naturally in thefood matrix, such as in the case of acrylamidebeing formed during the Maillardreaction between the amino acid asparagineand a reducing sugar (especially inpotato- and cereal-based, heat-treatedproducts). Alternatively, certain processingcontaminants, such as nitrosamines,can be formed by interaction of naturalfood components with food additives.Carcinogenic and genotoxic chlorpropanols,such as 3-monochloropropane-1,2diol (3-MCPD), are formed during theacid hydrolysis of wheat, soya and othervegetable protein products.Examples of other processing contaminantsinclude PAHs (in grilled andsmoked products), ethyl carbamate (inyeast-fermented alcoholic beverages andother products) or furan (in a variety ofheat-treated foods, especially coffee andcanned/jarred food).Food processing may also be a sourceof cross-contamination, such as contaminationof nonallergenic foods withknown food allergens.Migrants from Packaging MaterialsDirect contact of foods with packagingmaterials can result in chemicalcontamination caused by migration ofcertain substances into foods. Examplesof migrants of health concern may includebisphenol A or phthalates fromplastic materials, 4-methylbenzophenoneand 2-isopropylthioxanthone from inks,mineral oil from recycled fibers or semicarbazidefrom a foaming agent in theplastic gaskets that are used to seal metallids to glass packaging.ToxinsToxins are naturally occurring substancesthat are produced by variousorganisms, with mycotoxins and marinebiotoxins typically representing the majorconcerns in foods. Other examplesof toxins in foods may include bacterialtoxins (e.g., staphylococcal toxins) orcertain plant toxins, such as pyrrolizidinealkaloids that can be found in honey,milk or eggs. While the bacterial/fungalcontamination can be eliminated withThe Importance of Moisture in Samples Prior toChemical AnalysesMoisture content is an important consideration during sampling procedures, in part becauseit affects the extent of sample heterogeneity. It may be necessary to determine the moisturecontent through sample drying to express analytical results on a uniform scale.Precautions must be considered when drying foods at elevated temperatures, since chemicalreactions such as hydrolysis can occur and these reactions can be accelerated. Moisturedeterminations can be erroneous if hydrolysis has occurred, since the water of hydrolysis has notbeen released from the sample. A general rule of thumb for sample drying is that it should be asrapid and at as low a temperature as possible. Vacuum methods that can used to dry a sampleinclude vacuum ovens and lyophilization, or freeze-drying. Another method is microwave drying.Unlike external heating devices that operate through the sample vessel, microwaves rapidly heatthe sample, keeping temperature gradients to a minimum.For certain chemical testing applications, such as the presence of metals in food as well as theextraction of crude fat and nutrients from food, microwave digestion is the preparation methodof choice. The ability of microwave sample prep to dissolve almost any matrix, leaving targetspecies behind, provides preparative capabilities unavailable through other methods.The inherent variability in the composition of raw materials, basic ingredients and processedfoods requires the use of proper sampling and sample pretreatment techniques, in addition tostatistical methods for obtaining representative and replicate samples. Using the proper samplepreparation methodology can reduce analytical error and costly detection mistakes that couldjeopardize the safety of the food produced as well as lead to an even more costly food safetyrelatedrecall.14 F o o d S a f e t y M a g a z i n e