Different roasting hazelnut procedures alter the structure of the protein bodies and affect the binding capacities of IgEs from allergic children.

INTRODUCTION Thermal processing, commonly used during food production, may affect food allergenicity by inducing physical and/or chemical changes in proteins and lipids. However, due to the lack of detailed information on processing procedures, available evidences on this topic are presently contradictory. The aim of this study was to investigate how two different roasting techniques, hot air (HA) and infrared (IR), could modify the hazelnut seed structure, the protein profiles and solubility. Moreover, the ability of the IgEs from hazelnut allergic children to bind hazelnut proteins before and after roasting was evaluated. METHODS Experiments were designed on an Italian variety of C. avellana (Cv. Tonda Gentile delle Langhe) obtained from experimental fields. Two pilot-scale ovens infrared (IR) and hot air (HA) and two combinations of time and temperature for each oven were considered: 140 °C for 25 min (low temperature (LT)) and 170 °C for 17 min (high temperature (HT)) in HA; 140 °C for 12 min (LT) and 170 °C for 10 min (HT) in IR. RESULTS A decrease in hazelnut protein solubility was detectable following LT-IR roasting and it became more evident after HT processing, for both roasting types. The immuno-recognition decreased progressively from raw to high temperature processes. The IR-HT processing caused a quite complete disappearance of immune-recognition of hazelnut proteins. Interestingly, different allergens showed different responses to heat processing. The immune-reactivity of Cor a 9, Cor a 11 and Cor a 14 resulted to be stable until 140 °C, while Cor a 8 immuno-recognition was already reduced at 140 °C and completely lost at 170 °C. Differently, oil body (OB) associated protein immuno-recognition was increased after HA roasting at 140 °C whereas was reduced in the remaining treatments and disappeared in the IR-HT. At structural level, microscopical observations showed a cytoplasmic network disruption with an alteration of the structure of the protein bodies and of the cell wall organization. CONCLUSION IR oven is the least conservative processing, especially at high temperatures, both considering protein solubility and immuno-recognition. Our results could be useful for the development of clinical protocols for the process of oral desensitization of hazelnut allergic patients.