Fig. 4. Size exclusion chromatograms of soluble Ber e 1 in buffer pH 5.0 before (black line) and after (gray line) heating at 120 C for 20 min.
When Brazil nuts are used as an ingredient in, for example, cakes, the (crushed) nuts are usually mixed with the dough and distributed over the whole food product. The baking of such products generally implies heating temperatures ranging from 180 C to 230 C. Despite these relatively high temperatures, due to the water content in the crumb of these products, the temperature inside these crumbs will not exceed 100 C. As a result, Ber e 1 situated only at the outside of a food product can possibly denature during heat processing. The majority of Ber e 1, however, will be present in the crumb of the products, where the lower temperature will not induce the protein to denature.
In conclusion, in aqueous solutions with pH values between 5.0 and 7.0, a temperature exceeding 110 C is needed to denature Ber e 1. The denaturation temperature of Ber e 1 in Brazil nuts could, because of the low water content, is even higher than the temperature measured (Gekko & Timasheff, 1981). When using common heat processing methods, the largest part of foods normally do not reach temperatures > 100 C. This implies that Ber e 1 will always be consumed (mainly) in its native structure, having an intact immunodominant conformational epitope, and a high stability to pepsin digestion (Moreno et al., 2005). As a result, common heat processing techniques are not likely to affect the digestibility of Brazil nuts and its concomitant IgE binding capacity after digestion.