Synergistic effect of washing process and after-treatment parameters on gluten protein composition, rheological, and baking properties

Gluten was extracted from wheat flour with various modifications on lab scale. To assess the effect of process parameters, the washing water was tempered to either 20 °C or 50 °C and 0.1 M NaCl was added to the washing water. In an after-treatment process of the isolated gluten, 3 % of NaCl or 0.5 % of CaCl₂ was added. The wet gluten samples were subjected to either drying at 40 °C or freeze-drying. Different combinations of these parameters were used to study the synergistic effect of process and after-treatment parameters on gluten protein composition and functionality. The addition of salt and temperature treatment had synergistic effects on the functionality and composition of gluten proteins. The variability in the functionality of gluten proteins could largely be explained by their protein composition. In addition, gluten treated with salt had a positive effect on specific bread volume resulting in significant (p < 0.05) increases to 2.62 ± 0.06 cm³/g (20 °C, 0.5 % CaCl₂, freeze-dried) and 2.67 ± 0.07 cm³/g (20 °C, 0.1 M NaCl, 3 % NaCl, freeze-dried) compared to the control (2.08 ± 0.06 cm³/g). Inversely, crumb hardness decreased significantly (p < 0.05) to 203.5 ± 38.0 g and 198.0 ± 40.4 g compared to 585.7 ± 73.5 g, respectively. Moreover, the results indicate that changes in the gluten protein composition and functionality due to heat exposure during gluten extraction can be partially reversed by treatment with chloride salts, especially by adding 0.1 M NaCl during washing and 3 % NaCl in the after-treatment.