Preservatives, both naturally occurring and synthetically made, may be added to processed food to prevent spoilage, rancidity and mould growth. Examples of preservatives include nitrites and nitrates and their salts, butylated hydroxyanisol (BHA) and butylated hydroxytoluene (BHT), sulfites, and many others. According to the Canadian Food Inspection Agency (CFIA), preservatives are grouped into classes (I-IV), with each class having similar microbiological or chemical activity.
Class I: Curing preservatives in meats and cheeses
Class II: Antimicrobials
Class III: Antifungals
Class IV: Antioxidants and antioxidant synergists
All preservatives found in products in Canada must be approved for use by Health Canada. Preservatives are regulated as food additives and to be approved for use, detailed information about the preservative, its proposed use, its safety, and the effectiveness of the preservative for its intended use, must be submitted to Health Canada. Once approved, all preservatives in pre-packaged foods must appear on the list of ingredients on the packaging.
All food additives approved for use in Canada are listed in Division 16 of the Canadian Food and Drug Act. Section 4.3.1 of the Act outlines what is considered a ‘no preservative’ claim. A statement of ‘no preservatives added’ or ‘contains no preservatives’ may be allowed only if none of the additives listed under Division 16 of the Food and Drug Act have been directly added to the product, or added as a result of crossover. Crossover may occur if an ingredient in a product claiming ‘no preservatives added’ contains preservatives. ‘No preservatives added’ claims can also be made if the preservative used is naturally occurring, such as naturally occurring benzoates in cranberry juice, acetic acid in vinegar or citric acid in lemon juice.
Nitrates are naturally occurring chemicals present in soil, air, surface waters and ground waters. Nitrogen and oxygen combine to form the nitrate compound (NO3-), using three oxygen atoms and one nitrogen atom. A nitrate should not be confused with a nitrite (NO2-) which is formed from two oxygen atoms and one nitrogen atom. In nature, nitrates can easily be converted to nitrites and vice versa. Human exposure to nitrates and nitrites comes from water, food and air.
Just as nitrites and nitrates are found naturally in our environment, foods such as beets, celery, radishes and spinach are natural sources of nitrite and nitrate in our diet. Nitrates may also be found in some fish and dairy products such as cheese.
Nitrites are added to meat products during processing for two reasons:
1. To inhibit the growth of bacterial spores, and
2. To enhance colour.
Nitrites may be added directly to the meat product, but more frequently nitrates are added. The nitrates are converted to nitrites through natural bacterial fermentation and chemical reactions in the meat. Cured meat products have sodium or potassium nitrate (nitrate salts) added to them to preserve the meat product and prevent the growth of the bacterium Clostridium botulinum. C. botulinum can produce spores and causes botulism, a potentially deadly foodborne illness. Nitrites are used in pork, beef and poultry products to enhance colour. For example, nitrates are added to ham and bacon, giving them their characteristic pink colour. Some countries (but not Canada) permit the use of nitrites in fish products.
Some scientific studies suggest that nitrites promote and induce cancers in animals. When nitrites combine with certain amino acids, N-nitroso compounds or nitrosamines are formed and these have been shown to be carcinogenic (cancer-causing). In response to these findings, and the concern that excess nitrate/nitrite may react with the protein in the meat when it is cooked, to form these compounds, Health Canada has limited the amount of nitrate or nitrite that can be added to meat products to 200 parts per million (ppm). A complete ban on the use of nitrates and nitrites in foods has not been implemented because of the beneficial uses as preservatives and particularly their prevention of Clostridium botulinum growth. There is also some scientific evidence suggesting that low levels of nitrates and nitrites (below 200ppm) pose no health concern.
The nitrate and nitrite exposure we receive from air is negligible. Our primary source of exposure to nitrates and nitrites is through the food we consume, however exposure to these compounds can also occur through drinking water.
Sulphites are naturally occurring compounds in our body and the environment. They are primarily used as preservatives in food to maintain food colour, prolong shelf-life and prevent the growth of harmful micro-organisms. Sulphites can also be used in some pharmaceutical medications as a way of maintaining their potency.
There are no food safety concerns regarding sulphites; however certain individuals may be sensitive to their presence in foods. It is possible for sulphites to trigger asthma or an anaphylactic-type reaction. Certain individuals, particularly those with asthma, may react to sulphites with allergy-like symptoms. All pre-packaged foods required to have an ingredients list under the Canadian Food and Drug Act and Regulations, must list the presence of sulphites on the label. The pre-packaged food product label may include statements such as, “may contain” or “may contain traces of” sulphites and sulphite derivatives.
There are some exceptions to these regulations. Under the Food and Drug Act, some foods do not require ingredients lists. These foods do not have to declare the presence of sulphites, unless the amount of sulphite that is naturally occurring in, or added to, the product exceeds 10 parts per million (ppm). For example, wine in Canada is exempt from displaying a list of ingredients under B.01.008, and from declaring its components when used as an ingredient in another food under B.01.009, of the Food and Drug Act; however, many wines contain sulphites. Therefore, although it is exempt under B.01.009, when wine is used as an ingredient in a food and the final food product contains more than 10 ppm of sulphites, the presence of sulphites must be declared in the list of ingredients. The total amount of sulphites in the product may be because of the addition of the wine, or because of the combination of the wine and other ingredients. For more information about how products containing sulphites are labelled, visit the Canadian Food Inspection Agency’s website:http://www.inspection.gc.ca/english/fssa/labeti/allerg/allergee.shtml
If you are someone who is sensitive to sulphites or wishes to avoid them for other reasons, it is important to always read the ingredients’ lists and remember that sulphite derivatives exist and may be listed as:
E 220, E 221, E 222, E 223, E 224, E 225, E 226, E 227, E 228 (European names)
For more information on possible food and non-food sources of sulphites as well as information on sulphite allergic reactions, please see Health Canada’s website at: http://www.hc-sc.gc.ca/fn-an/securit/allerg/fa-aa/allergen_sulphites-sulfites_e.html
The University of York and the Chemical Industries Association in the United Kingdom have built a website on food additives, which you can search either by name or by E-number:http://www.understandingfoodadditives.org/pages/Ch6p1.htm
Canadian Food Inspection Agency. (2008). Questions and Answers Regarding the Labelling of Food Allergens. Retrieved from,http://www.inspection.gc.ca/english/fssa/labeti/allerg/allergee.shtml
Department of Justice Canada. (2008). Food and Drugs Act. Retrieved from,http://laws.justice.gc.ca/en/showtdm/cr/C.R.C.-c.870
Epley, R.J., Addis, P.B. and J.J. Warthesen. (1992). Nitrite in Meat. University of Minnesota Extension. Retreived from www.extension.umn.edu/distribution/nutrition/DJ0974.html
Food Additives and Ingredients Association. (n.d.). E-Numbers. Retrieved from,http://www.understandingfoodadditives.org/pages/Ch6p1.htm
Health Canada. (2007). Sulphites - One of the nine most common food products causing severe adverse reactions. Retrieved from, http://www.hc-sc.gc.ca/fn-an/securit/allerg/fa-aa/allergen_sulphites-sulfites-eng.php
Health Canada. (2008). Food Additives. Retrieved from, http://www.hc-sc.gc.ca/fn-an/securit/addit/index_e.html
University of Idaho. (1997). What is the evidence for a link between preservatives and cancer and other toxic effects? Retrieved from,http://extoxnet.orst.edu/faqs/additive/preserca.htm