Testing for Allergens

It has been estimated that in Britain alone, several million people have some form of food allergy or food intolerance. World-wide therefore, the figure is likely to run in to hundreds of millions. Whilst the biggest proportion of food intolerance is merely inconvenient or uncomfortable, for a significant minority of people, a food allergy can prove fatal.

US and European perspectives

In May of 2001, a coalition led by the National Food Processors Association and consumer groups in the US developed voluntary guidelines calling for manufacturers to label prominently those foods containing peanuts, eggs, soy, wheat and four other potentially life-threatening allergens. This initiative was followed up in August of that year by the US Food and Drug Administration (FDA) which published guidance notes for FDA investigators and inspectors in evaluating conditions that may result in the introduction of undeclared allergens into foods.

More recently, the European Union has begun to take the issue of allergens more seriously. In October 2001, The European Commission issued a proposal for an amendment to the Food Labelling Directive (2000/13/EC) to abolish the "25% rule". This proposal was published in the C-series of the Official Journal (OJ C332E, 27/11/01, pp. 257-259), during November 2001 and was implemented by enforcing legislation in 2004.

The amendment now requires that all ingredients intentionally added will have to appear on the label. The proposal also establishes a list of ingredients liable to cause allergies or intolerances and is intended also to apply to alcoholic beverages if they contain an ingredient on the allergen list. The list of allergenic ingredients to be labelled was given as follows:

• Cereals containing gluten and products thereof
• Crustaceans and products thereof
• Eggs and products thereof
• Fish and products thereof
• Peanuts and products thereof
• Soybeans and products thereof
• Milk & dairy products (including lactose)
• Nuts & nut products
• Sesame seeds and products thereof
• Celery and products thereof
• Mustard and products thereof
• Sulphite at concentrations of at least 10mg/Kg

Meeting the regulations

As ever, it is one thing to have legislation requiring the adequate declaration of allergenic ingredients, but it is quite another matter for manufacturers to set up systems and procedures that ensure they can meet their legislative obligations. In a previous issue of FIAI, we discussed the manufacturing controls necessary to prevent cross contamination. An important aspect of these controls is the verification offered by testing.

Testing is essential because it is not always obvious what ingredients are being used in any given food product that may already contain allergenic material, or have been exposed to the risk of cross contamination. Some time ago the laboratories at RSSL investigated a customer complaint relating to ground spices. These had caused problems for a consumer with a known allergic reaction to peanuts. Analysis showed that the spices were indeed contaminated with peanut protein, although the spice packer was adamant that this could not be the case. On further investigation, it transpired that the company that ground the spices on behalf of the packer was also spraying them with 'refined' peanut oil. Unfortunately, the oil was not very well refined, and peanut protein was getting through to the product.

Setting up a laboratory

In setting up an allergens testing laboratory it is important to consider and counteract all the same risks of cross contamination that exist on the factory floor. Issues such as segregated storage and the thorough cleaning of work tops and equipment are just as important to the laboratory environment as to the manufacturing environment.

Ironically, the mammalian defence mechanism against food allergens has provided the food industry with reliable methods for their detection. Tests are now available for different allergens such as peanut proteins, casein, gluten, lactoglobulin, histamine, egg allergens and soya. All these tests are based on a highly sensitive, specific and relatively rapid analytical technique known as Enzyme Linked Immunosorbent Assay (ELISA). Lactose can also be detected by HPLC methods. RSSL has also developed a vast array of DNA methods for detecting and differentiating between several different nuts as well as other allergenic properties.

Put very simply, the ELISA method uses specific antibodies to selectively bind to a given allergen (e.g. peanut protein) assuming it is present in the food.  Following a cascae of a number of different biological reagents the presence of the extracted allergen is ultimately revealed by a colour change reaction involving an allergen bound enzyme. The intensity of the colour change is an indication of the quantity of allergen present.

Using test kits based on ELISA technology, it is possible to detect peanut proteins in foods at extremely low concentrations (0.15 parts per million). Tests for other allergens such as casein and gluten are sensitive to concentrations as low as2.5ppm and 10ppm respectively.

Although the operation of the ELISA procedure is fairly routine, the true biochemistry lies in being able to reliably extract various allergenic properties from a variety of 'difficult' food matrices.

Both ELISA and DNA based tests are used routinely by RSSL on behalf of retailers, manufacturers and ingredient suppliers both to clear ingredients prior to use, or to investigate customer complaints following some adverse reaction to a product. Where contamination has occurred, it may even be possible to establish the point at which contamination has taken place.

Growing importance

The issue of allergenicity is likely to increase in importance. This is because more people seem to be developing allergic responses to different foods, perhaps as a consequence of our more varied diets, but also because medical science is now more capable of identifying the dietary factors that are causing illness in some consumers. For the food processing and ingredients businesses, the challenge is to keep abreast of the science, to gain a better understanding of our products and to identify, then label or remove the potential allergens within our products.