Effects of Pressure and Thermal Processing on Chestnut in vitro Allergic Reactivity

Abstract

Tree nuts are primarily responsible for fatal allergic reactions. Thermal and non-thermal treatments are mainly carried out in industry to improve food quality. Food processing can modify the structure and function of food proteins and may alter their allergenic properties. We hypothesized that pressure and thermal treatment, could modify chestnut in vitro allergenicity. An ambispective study was carried out, including sera from patients, evaluated between 2006 and 2016, with clinical allergy to chestnut, confirmed on the basis of either a convincing history of anaphylaxis with positive skin prick test and/or specific serum IgE levels to chestnut by the fluorescent enzyme immunoassay, or a positive double-blind placebo-controlled food challenge. Immunoblotting was performed in the untreated and treated chestnut extracts (boiling 30 and 60 minutes, and heat/pressure treatment at 121º and 138º Celsius during 15 and 30 minutes), and determined the effects of those treatments over the IgE binding capacity of each allergen , quantifying them by ELISA. Sera from 25 patients were analyzed. The results showed IgE-binding proteins around 25 KD, 37 KD and 50 KD. A consistent IgE-reactivity decrease after boiling and heat/pressure treatments was observed in IgE-ELISA. The IgE reactive bands disappeared completely in many cases. The results of our study indicate that pressure and thermal treatments were able to decrease the IgE-binding properties of chestnut protein extracts evaluated in IgE-ELISA and IgE-western blot. It did not seem that any of these treatments increased chestnut allergenicity.