Optimization of Quinoa‐Based Gluten‐Free Bread Production Using Microbial Transglutaminase Enzyme and Hydroxypropyl Methyl Cellulose ( <scp>HPMC</scp> ) by Response Surface Methodology

Celiac is an autoimmune disorder that is triggered by gluten proteins. Bread is the staple foodstuff in which gluten networks play a detrimental role. This study investigated the optimization of transglutaminase (TG) and hydroxypropyl methylcellulose (HPMC) using Response Surface Methodology (RSM) and central composite design (CCD) to simulate the functionality of gluten proteins in quinoa-based gluten-free bread. The concentrations of TG and HPMC varied within the ranges of 0%-1.5% w/w and 0%-2% w/w, respectively. A model was ultimately developed using the CCD and the specified range values for the two factors, with measurements taken for specific volume (SV), moisture content (MC), overall acceptance (OA), and hardness. The study identified optimal values of 0.414 g/100 g for TG and 1.283 g/100 g for HPMC, achieving specific values of 2.320 cm³/g for SV, 39.161% for MC, 7.454 for OA, and 5431.121 g for hardness, with a desirability of 0.983. To verify the presented model, the bread quinoa sample produced with formula (F1) was evaluated and then compared with the control samples (quinoa bread in the absence of TG and HPMC (F2) and wheat bread (F3)) in terms of rheological properties, microstructure, and physicochemical properties. Among the gluten-free breads (F1 and F2), improvement in all parameters has been achieved through the incorporation of TG and HPMC. This improvement demonstrates the effectiveness of TG and HPMC to well mimic the functional characteristics of gluten in gluten-free breads. Despite more uniform distribution of air bubbles at F1, its higher MC and lower SV compared to F3 verified its lower water migration through the baking process.