Résumé:
The aim of this thesis was to study the effects induced by Instant Controlled Pressure Drop (DIC) and microwaves on the functional, structural and immunological properties of wheat gluten proteins in order to diversify foods for people suffering from celiac disease. The response surface methodology was applied to study the linear, quadratic and interaction effects of the factors involved. In the first part, the gluten powder prepared from the wheat flour was treated by the DIC according to central composite design with two factors, temperature between 100 and 165 ° C and time between 20 and 60 s. Gluten proteins DIC treated were separated by SDS-PAGE and two-dimensional electrophoresis. In addition, the content of free thiols, solubility, emulsifying and foaming capacity and immunoreactivity were measured. In the same part, the prepared gluten powder and three types of wheat-based breads were processed by another more intense central composite design, temperature between 100 and 165 ° C and time between 40 and 120 s. The reactivity R 5 after peptic and tryptic digestion of these samples was measured. In the second part, the commercial gluten powder was processed by microwave according to central composite design with two factors, power between 200 and 1000 W and time between 20 and 60 s. After treatment, several parameters were measured such as the maximum temperature reached after the microwave treatment, the water content, the content of various gluten proteins, the content of free thiols, the abundance of the secondary structure and the macromolecular characteristics of polymers, extractability of gluten proteins, maximum resistance to extension (Rmax), total extensibility (Ext) and R5 reactivity after peptic and tryptic digestion. Electrophoretic separation was also carried out. After DIC treatment, wheat gluten became rigid, which is due to a significant increase in β structures. A significant loss of α-helices and a significant increase in intermolecular β-sheets and the rearrangement of disulfide bonds signify the denaturation of wheat gluten proteins. The rheological properties were totally lost after DIC treatment. However, the primary structure was not affected. The DIC treatment affected functional properties. The lowest protein solubility, emulsifying capacity and foaming capacity were obtained under the highest DIC processing conditions (165 ° C, 60 s). The immunoreactivity of anti-gliadin IgA celiac antibodies in wheat gluten treated with DIC was increased overall. The increase in toxic epitopes of gluten and DIC-treated breads demonstrated the inability of this treatment to reduce their immunoreactivity. Regarding the microwave treatment, the water content decreased and the temperature of the glutens measured after treatment increased. The content of extractable gliadins was affected by this treatment, while the content of extractable glutenins was not. The alteration of the secondary structure is related to the disaggregation of the polymers observed. In addition, microwave treatment increased the amount of potentially toxic epitopes released after digestion, showing the ineffectiveness of this treatment in detoxifying gluten for patients with celiac disease.
