Comparison of new immunofluorescence method for detection of soy protein in meat products with immunohistochemical, histochemical, and ELISA methods

Soy proteins are commonly used in the food industry thanks to their technological properties. However, soy is, along with cow’s milk, eggs, wheat, peanuts, tree nuts, fish, crustaceans, and molluscs, responsible for around 90% of food allergies, and is also one of the foodstuffs that can cause anaphylaxis. The aim of this work was to compare the immunofluorescence method for the detection of soy protein in meat products purchased from the retail market with other microscopic methods (immunohistochemical and histochemical), with the ELISA reference method and with the confirmatory results. Within the research, 127 meat products purchased in the retail network were examined using the immunofluorescence method used for the detection of soy protein. The method was compared to Enzyme-Linked ImmunoSorbent Assay (ELISA), immunohistochemical, and histochemical methods. According to McNemar’s test, noncompliance between the immunofluorescence method and immunohistochemical method was low. In addition, a significant difference between the fluorescence method and ELISA (P < 0.05) and a highly significant difference between the fluorescence method and histochemical examination (P < 0.01) was found. The immunofluorescence method was also compared with confirmatory results. According to McNemar’s test, non-compliance between the immunofluorescence method and confirmatory results was low. The results showed the possibilities of this new method to detect the content of soy protein in meat products. Fluorescence microscopy, meat products, soybean, foodstuffs, allergy Soy protein is added to meat products due to its unique functional properties, such as water and fat absorption, creating texture and emulsifying ability. On the other hand, in the United States alone, soybean ranks among 8 major food allergens and has been credited with more than 90% of food borne allergies (Kabourek and Taylor 2003). Estimates of thresholds inducing undesirable reactions in persons allergic to soy protein differ significantly and values between 0.0013 and 500 mg have already been published (Becker et al. 2004; Ballmer-Weber et al. 2007). Clinical manifestations of soy allergies include digestive problems, respiratory diseases (rhinitis, asthma), skin reactions (urticaria, atopic eczema), and IgE-mediated systemic reactions (Batista et al. 2007). The issue of food allergens is enshrined in the legislation of the European Union, namely in Directive 2003/89/EC amending Directive 2000/13/EC as regards indication of the ingredients present in foodstuffs. In order to avoid misleading consumers and also to protect allergic consumers, analytical methods for determination of soy protein in meat products have been developed. Most of these methods are based on the electrophoretic, immunochemical or chromatographic techniques. The reference method used in determination of soy protein in products is the immunochemical method ELISA. Other options are microscopic methods which were for the purposes of soy protein detection in meat products combined with staining techniques: Gomory staining, modified by Grocott, or trichrome staining by Charvat (Heckmann et al. 1992). Among microscopic methods for detecting plant proteins, the most reliable are immunohistochemical methods. These methods were used