Development of sandwich ELISA and lateral flow immunoassay to detect almond in processed food.

Almond (Prunus dulcis) represents a potential allergenic hazard that should be included in Allergen Control Plans. In this study, sandwich ELISA and lateral flow immunoassay (LFIA), using amandin (Pru du 6) as the target protein, were developed to detect almond in processed food and validated according to international guides. ELISA could detect 2 ng/mL and LFIA 30 ng/mL of pure amandin. No cross-reactivity was found on a panel of 50 food commodities with the exception of Pecan nut, Brazil nut and chestnut for which the cross-reactivity was lower than 0.02%. Furthermore, ELISA and LFIA were able to detect 0.12 and 0.70 ppm of almond protein in foods spiked with almond extract whereas 0.20 and 2.0 ppm could be detected in baked cookies incurred with almond, respectively. Both techniques could be applied for food manufacturers and control agencies for monitoring the presence of almond traces in food and working surfaces.

Influence of different extraction conditions on the detection of glycinin and ß-conglycinin in model processed foods by ELISA.

The presence of undeclared soy proteins in food can cause severe reactions in soy allergic individuals. The extraction of target proteins from processed foods is a crucial step in allergen detection by immunoassays, as only successfully extracted target proteins can be detected by the specific antibodies. The effectiveness was studied of different conditions (type of buffer, temperature and time of incubation) on the extraction of total protein, and concentration of glycinin and ß-conglycinin from different food matrices. The yields were determined using a soy protein isolate and three processed foods (sausage, bread and pâté) incurred with soy proteins. The yields were affected by the processing of analysed products and the composition and pH of the extraction buffers. Neutral and alkaline buffers (pH from 7.4 to 10.6) exhibited good protein extraction capacity and detectability of the specific target proteins. Denaturing additives and highly alkaline buffer (pH 12) extracted more crude protein but they were incompatible with the ELISA assay. Overall, the best results were obtained using phosphate (pH 7.4) and Tris/HCl (pH 8.5) buffers in the presence of 0.5 M NaCl. Crude protein yield of food extracts did not correlate with that of glycinin and ß-conglycinin, whereas a good relationship was found between the yields of the two proteins.

Effect of high pressure and pulsed electric field on denaturation and allergenicity of Pru p 3 protein from peach.

The effect of high pressure (HP) and pulsed electric field (PEF) treatments combined or not with heat on denaturation and allergenicity of Pru p 3, the major allergenic protein of peach, was studied. Denaturation of Pru p 3, determined by ELISA using rabbit IgG, occurred when the protein was treated at 500 and 600 MPa at 20 °C and at 400 MPa at 50 °C. PEF treatment at 25 kV/cm at 50 °C denatures Pru p 3. Allergenicity of Pru p 3 was estimated in vitro by a competitive fluorescent immunoassay using three pools of sera from peach allergic patients. Any treatment applied did not show to influence the binding of Pru p 3 to IgE. When HP and PEF treated samples were tested by the prick test, the skin response was dependent on the particular sensitization of each patient, obtaining an increased reaction in more than 50% of individuals.