Effect of Roasting on the Conformational Structure and IgE Binding

Sesame can trigger a systemic allergic reaction. In the present study, we investigated the responses of the structure and IgE binding of sesame allergens to different roasting treatments (120, 150, and 180 degrees C for 5 to 30 min). We analyzed the tryptic digestion peptides using a label-free mass spectrometry method. The total amount of soluble proteins in sesame was significantly reduced by roasting at 180 degrees C, followed by 150 degrees C. Ses i 1 was the most stable protein during processing as it still possessed a higher protein abundance compared to other allergens after roasting under 180 degrees C. The most unstable allergens were Ses i 4 and Ses i 7, which suffered severe protein degradation at 180 degrees C. Roasting at 180 degrees C remarkably increased the secondary structure content of alpha- helices but decreased that of beta-sheets, whereas roasting at 120 and 150 degrees C had a limited effect on the secondary structure of sesame proteins. Moreover, serum pool Western blot analysis showed that the main allergens were oleosin of Ses i 4 and Ses i 5. The IgE-binding ability of sesame allergens was significantly decreased under 180 degrees C roasting, as well as the solubility of sesame proteins, which showed remarkable congruence in changes. Relative quantification results indicate that individual sesame allergens respond differently to the roasting process. In general, sesame allergens are unstable under roasting treatment. Therefore, the allergenic potential of sesame allergens may be minimized by selecting appropriate parameters during processing.