Production of wheat gluten hydrolysates with improved functional properties: Optimization of operating parameters by statistical design

Native wheat gluten is a deluxe bread improver and may be utilized as a functional protein additive in multifarious non-bakery foodstuffs due to its desirable structure-enhancing properties. Also its utilization would be economically interesting, but lack of some desirable functional properties limited their expanding utilization in foodstuff formulations. This study was designed to examine the relationship between process parameters and functional properties of the obtained hydrolysates using Box-Benken experimental design and response surface methodology (RSM). The hydro-lysate showing the highest improvement of solubility and foaming ability was further separated by sequential ultrafiltration to obtain molecular weight distribution profile. The progress of wheat gluten hydrolysis was followed by monitoring the degree of hydrolysis (DH) using the pH-stat method and functional properties were measured by our methods already adopted. The effects of process parameters (pH, T, [S], [E]/[S] ration) and their interactions were investigated by the means of the four-factor Box-Behnken experimental design with 29 experimental points (5 central points). Experiments were carried out in triplicates and expressed as means with SD. The effects of different parameters under the significance level of p < 0.05 were examined using one-way analysis of variance (ANOVA) and Student t-test. The coefficients of the response function and their statistical significance were evaluated by the response surface regression analysis, using the Design software. Non-significant terms (p ≥ 0.05) were deleted from the second order polynomial and a new polynomial has been recalculated. The Fisher test (F-value) was used to determine whether the second-order model was adequate to describe the obtained data while the goodness of fit of the model was evaluated by the determination coefficient (R2). The obtained results showed that the second-order models developed for DH, solubility and foaming prop