Effect of Processing on the Structure and Allergenicity of Peanut Allergen Ara h 2 Roasted in a Matrix

Peanut allergy is the leading pediatric food allergy. Many attempts have been made to reduce its allergenicity by processing. After roasting, Ara h 2 and its derivatives in the matrix were isolated by immunoaffinity chromatography (IAC). The structure and allergenicity of Ara h 2 were analyzed by circular dichroism, mass spectrometry (MS), western blotting, the enzyme-linked immunoassay, and cell modeling. Our results showed that a large portion of Ara h 2 was fragmented and cross-linked. Ara h 2 monomers accounted for only 13% of the total proteins after IAC purification. In addition, the structure of Ara h 2 changed after roasting. In addition to methylation and oxidation modification, the disulfide bonds of Ara h 2 were found to be rearranged after roasting. In the conformational structure of Ara h 2, the content of the α-helix decreased from 27.1 to 21.6% after roasting, while the content of the random coil increased from 29.1 to 34.3%. Six cleavage sites of trypsin were exposed, while three were covered. In terms of allergenicity, most of the cross-linking products were not recognized by patients' sera. Only one faint band around 40 kDa was observed in our blotting. For Ara h 2 monomers, roasting enhanced their IgE binding capacity and ability to stimulate the degranulation of basophils. The potential allergenicity increase of Ara h 2 monomers did not reflect the allergenicity change of Ara h 2 in the matrix due to the amount and property of its derivatives after roasting.