Powerpoint

Allergenicity and Detection Methods of Soybean : 

Allergenicity and Detection Methods of Soybean Shanghai Entry-Exit Inspection and Quarantine Bureau

Aims of the session : 

Aims of the session Soybean and soy products Allergenicity of Soybean Hypoallergenization of soybean Detection methods

1. Soybean and soy products : 

1. Soybean and soy products Soy provided food and oil for Asian countries for thousands of years. The soybean is today the world’s foremost provider of protein and oil. World soybean production reached 230 million metric tons,and soybean meal represented about 70% of the world total protein meal consumption in 2007.

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The soy products: soy flour, lecithin, oil, soy protein concentrate, soy protein isolate, etc. Soy protein products are widely used in foods,cosmetics and pharmaceutical industry.

2. Allergenicity of Soybean : 

2. Allergenicity of Soybean Soybeans are wildly used in processed foods because of their excellent nutritional and functional properties, and soy allergy is important. A prevalence rate of 0.3-0.4% in the general population. 6% atoic children 14% hildren with cow’s milk allergy

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2.1 Symptoms range from mild to severe, with most individuals suffering from just a few of the many possible symptoms. respiratory problems (rhinitis, asthma, throat swelling) gastrointestinal problems (nausea, vomiting, diarrhoea, abdominal cramping) or skin problems (hives, itching, dermatitis, eczema)

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Threshold levels for triggering allergenic reaction have been reported to vary from 0.0013 mg to 500mg.

2.2 Allergenic proteins : 

2.2 Allergenic proteins Multiple allergenic proteins have been documented in soybean extracts. at least 16 allergenic proteins (1)Gly m Bd 30k(P34) major allergen, 65%. 34 kDa oil body associated protein seed storage protein

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(2)Two additional proteins, the beta subunit of conglycinin (Gly m Bd 60 K) and a vicilin-like glycoprotein (Gly m Bd 28 K), are considered to be major allergens. (3)Minor allergens include soybean trypsin inhibitor and members of the glycinin protein family.

2.3 Treatment/control : 

2.3 Treatment/control There is no cure for food allergy. Complete and strict avoidance is the only way to prevent a reaction. stringent labeling regulations and quality-assurance procedures (HACCP)should be enforced.

3. Hypoallergenization of soybean : 

3. Hypoallergenization of soybean soybeans as food sources/supplements can be found in approximately 6,000 foods. In most cases ,soybeans are not labeled on the commodity. in trace quantities, e.g. as “hidden allergens” or as contaminants As avoidance is difficult, hypoallergenic food or a food with little or no allergen that can be safely ingested by food allergic individuals is developed.

3.1 Food processing : 

3.1 Food processing Thermal Treatment Enzymatic Hydrolysis Chemical Modification

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(1)Thermal Treatment Heat processing cannot reduce/eliminate soybean allergens in food completely. Heat treatment can alter protein structure, and reduce allergenicity partly. Heat treatment may also create new allergenic epitopes.

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(2)Enzymatic Hydrolysis Hydrolysis has been generally recognized to reduce the antigenicity of proteins. It is rather difficult to affirm if any of these hydrolyzed soybean products are safe for the larger populationof soybean allergenic individuals.

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(3)Chemical Modification Several reports describe reduction of soybean allergenicity by allergen conjugation with polysacchride.

3.2 Breeding and Genetic Modification : 

3.2 Breeding and Genetic Modification Breeding and mutagenesis have both been presented as technologies that have the potential to reduce soybean allergenicity.

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altering soybean to reduce their ability to initiate an allergic reaction through genetic modification gene silencing (soybean allergens).

4. Detection methods : 

4. Detection methods Both industry and law-enforcement institutions need reliable methods to detect allergenic foods at relevant levels in complex food products. The methods employed are either targeting the allergen (protein) itself or a marker that indicates the presence of the offending food. As markers for the presence of potentially allergenic food products or ingredients, specific proteins or DNA fragments are targeted.

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Protein-based methods ELISA : Commercially available dip-stick assays /lateral-flow assay DNA-based methods PCR methods: Commercially available Biosensors developing

4.1 ELISA assays : 

4.1 ELISA assays Routine detection method The ELISA assays are highly specific for the respective food and depend largely on the molecular recognition of the employed food-specific antibodies. Any changes in the protein structure in a food due to processing will inevitably affect the performance of the assay.

4.2 PCR methods : 

4.2 PCR methods Routine detection method PCR methods are the high specificity and the relatively high stability against environmental and technological influences. PCR results cannot be linked to any allergen/ protein content.

4.3 Commercially available test kits : 

4.3 Commercially available test kits

4.4 Method considerations for allergen detection in foods : 

4.4 Method considerations for allergen detection in foods Sensitivity Specificity Matrix and processing effects Method validation Reference materials

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(1)Sensitivity Methods must be sensitive enough to specifically detect the allergens or allergenic foods in those amounts that might trigger allergic reactions in sensitized individuals. lower detection limits (LOD) for allergens in different food products need to be in the low ppm (mg/kg).

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(2)Specificity Methods need to specifically detect the allergenic food of concern, but not necessarily only one specific allergenic protein (or epitope) of a particular food, as different proteins may be affected differently by varied processing steps and even allergic consumers might react differently to various allergens of the same food. However, a highly stable allergen may serve as a marker substance in the analysis of the respective allergenic food.

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(3)Matrix and processing effects The matrix of a particular food can mask the allergen and likewise antibody binding sites can be hidden or exposed after food-processing steps. These effects can impair the detection/quantification of food allergens by at the same time retaining the original allergenicity.

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(4)Reference materials To compare results and standardize/calibrate test systems, internationally recognized reference materials are needed. However, so far no certified reference materials for allergen analysis in foods have become commercially available.

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(5)Method validation Validation of the available methods is important to show that they are fit for the purpose to assure food safety for allergic individuals and to determine the absence/ presence of certain ingredients/contaminants in food products. Method validation establishes performance criteria such as detection limit, recovery, accuracy and precision of the method.