Effect of heat, pH and shear on digestibility and antigenic characteristics of wheat gluten

Abstract

Processing-induced conformational changes may affect digestibility and antigenic potential of food proteins. In vitro gastrointestinal digestibility of gluten proteins was established after treatment at various pH (3 or 7), temperature (room temperature or 100 °C) and shear (0 or 1500 s−1). Electrophoretic patterns (SDS-PAGE) of the resulting hydrolysates and antigenicity (ELISA and immunoblotting) of gliadin fraction of the proteins were also studied. Digestibility was positively correlated with α-helix/β-sheet ratio. Lower antigenic reaction shown by digested hydrolysate of gluten samples treated at pH 3 and room temperature was ascribed to its acidic deamidation and improved digestibility. Further heating to 100 °C slightly increased antigenicity. In contrast, hydrolysate of gluten at pH 7 and room temperature exhibited highest antigenicity, attributed to partial resistance of α-/β-gliadin to digestion and appearance of some new potentially antigenic polypeptides. However, heating at 100 °C caused heat-induced protein aggregation, consequently lowered digestibility and availability of antigenic components resulting in a minimum (60 % reduction) antigenicity. Overall, shear had no effect on digestibility and antigenicity irrespective of pH and temperature. Thus, antigenic potential of gliadins can be minimized by selecting appropriate parameters during processing.