Quantification of Ara h 1 in peanuts: why roasting makes a difference

Summary Background Increased allergenicity of roasted vs. raw peanut has been reported by showing higher IgE binding to roasted peanut extracts. Objective To study the effect of roasting on Ara h 1 quantification in peanut using a specific monoclonal antibody‐based ELISA, and to compare the Ara h 1 content from different kernel size peanuts from four runner cultivars. Methods Raw or oven‐roasted (177°C for 5–30 min) runner peanuts were crushed and extracted at 60°C. Inhibition ELISA was used to study binding of Ara h 1 purified from raw or roasted peanut. Runner peanuts of four different cultivars were collected, shelled, sized and roasted for 15 min at 177°C. Ara h 1 in the extracts was compared by ELISA. Results Ara h 1 levels were up to 22‐fold higher in roasted than in raw peanuts (820 vs. 37 μg/mL, in a representative experiment) with an Ara h 1 peak at 10–15 min of roasting. Inhibition ELISA indicated that this increase was not due to conformational changes in the Ara h 1 monoclonal antibody epitopes. Ara h 1 was found at lower levels in number 1 than in jumbo‐ and medium‐sized peanuts, and no differences were found among cultivars. Conclusion These results suggest that roasting increases the efficiency of Ara h 1 extraction, and/or that the monoclonal antibody binding epitopes were more accessible in roasted peanut. Expression of Ara h 1 is associated with peanut maturity.