Proteomic Characterization of Processed Hazelnuts: Implications for Hypoallergenic Food Development

Hazelnut allergy represents one of the most common food allergies, often associated with severe IgE-mediated reactions [1]. Advanced techniques such as proteomics and genomics allowed to identify several hazelnut proteins responsible for triggering allergic reactions in sensitive individuals. These proteins tend to be highly stable and resistant to digestion, which increases their potential to provoke an immune response [2]. Additionally, the allergenic properties of hazelnut proteins can be influenced by food processing methods. Certain treatments - such as hydrolysis, fermentation, and heating - have been explored and optimized to modify or reduce their allergenicity [3-5]. This study investigates how specialized processing - moving beyond simple thermal treatment - can modulate the hazelnut proteome for hypoallergenic applications. The experimental design focused on the synergistic effect of moisture and pressure: roasted hazelnut kernels and derivative powders were first hydrated in water and subsequently subjected to high-pressure saturated steam in an autoclave at 134 °C for 10 minutes. This thermo-hydrometric treatment aims to induce deep structural modifications in allergenic proteins. Protein extracts from native and processed samples were analyzed using a bottom-up proteomic approach via UHPLC-ESI (+)-ddHRMS, complemented by targeted Selected Ion Monitoring (SIM) to track specific peptides. Identified proteins were subjected to in silico allergenicity assessment by querying the Immune Epitope Database (IEDB). Particular attention was devoted to major hazelnut allergens, such as Cor a 8 (Lipid Transfer Protein) and Cor a 9 (11S Globulin), specifically targeting peptide sequences associated with known IgE-binding epitopes. The results revealed significant alterations in protein profiles following processing, with evidence of reduced detection of specific allergenic proteins and marked modifications in peptide patterns. Epitope mapping suggested a substantial decrease in sequences associated with allergenic potential indicating that the applied treatments effectively compromise the structural integrity and potential immunoreactivity of hazelnut proteins. The investigation highlighted that the high-pressure saturated steam treatment (autoclave), particularly when preceded by hydration (HA samples), was significantly more effective in reducing the presence of most allergenic epitopes compared to dry-treated (A samples) or untreated controls. Notably, the sample matrix influenced the response: hazelnut powders showed a more pronounced and variable reduction in specific sequences compared to whole roasted kernels. Autoclaving appears promising for producing hypoallergenic ingredients, but residual allergenic peptides persist, requiring further optimization. The study supports mass spectrometry–based proteomics for allergenicity assessment, with future work including in vitro digestion and clinical validation to confirm safety.