Effects of Enzymatic Hydrolysis Followed by Polyphenol Treatment on the IgE-Binding and Structure of Peanut Protein Extract

Reducing peanut allergenicity by enzymatic hydrolysis and polyphenols has been studied by many researchers but none of reported studies have demonstrated the complete elimination of allergenic potential. This study investigated the effects of extensive hydrolysis and polyphenol-peptide interaction on the IgE-binding of peanut protein hydrolysate (PPH), characterized the major allergenic fragments resistant to Alcalase hydrolysis and the influences of polyphenol extracts from grape pomace (GPE), green tea (GTE), and peanut skin (PSE) on the solubility and IgE-binding of peptides, and the shifts of protein/peptide secondary structures in PPH. Alcalase hydrolysis of peanut protein for 2–8 h resulted in PPH with a degree of hydrolysis (DH) of 34–43%. The IgE-binding of PPH decreased with increasing DH and maximum reduction was observed at DH 42–43%. Two dominant Alcalase-resistant peptides reactive to peanut-specific IgE were identified by Western blot, LC-MS/MS and sequence mapping techniques, and they exhibited 81.82% and 74.19% similarity with the acidic and basic subunits of Ara h 3, respectively. The interaction between PPH and polyphenol extracts from grape pomace, green tea, and peanut skin resulted in precipitation of IgE-reactive peptides. Western blots showed enhanced IgE-binding signal in GTE- and PSE-treated PPH precipitates. FT-IR revealed that GPE and GTE at higher concentrations increased α-helix, decreased β-sheet and β-turn, while PSE induced β-sheet formation. Overall, extensive hydrolysis with Alcalase effectively reduced most IgE-binding epitopes; the effect of subsequent polyphenol interactions on PPH allergenicity needs in vivo validation.