How Do Xanthan and Hydroxypropyl Methylcellulose Individually Affect the Physicochemical Properties in a Model Gluten-Free Dough?

To better understand the physicochemical changes imparted by hydrocolloids on gluten-free dough, 2 hydroxypropyl methylcelluloses (HPMCs) and xanthan gum were added at 2%, 3%, and 5% to rice cassava dough without the addition of alternative proteins. The formulated doughs were analyzed using thermoanalytic and rheological techniques to determine the role of water and subsequent flow behavior upon hydrocolloid addition. The baked loaves were then measured for specific loaf volume and tensile strength to determine bread quality. Thermogravimetric analysis (TGA) results revealed that hydrocolloid-added dough held water more tightly than the rice cassava control with an additional water distribution at 85 to 88 degrees C. Rheologically, the increase of elastic moduli in the low methoxy HPMC and xanthan-added dough became more pronounced with gum addition; however, both HPMC formulations had increased viscous moduli allowing the gas cells to expand without collapsing. In the bread, the final specific loaf volume increased with high methoxy HPMC (2% to 5%) and low methoxy HPMC (2%) but was depressed with increased addition of low methoxy HPMC (5%) and xanthan (3% and 5%). Crumb hardness was decreased in high methoxy HPMC loaves but was increased significantly in low methoxy HPMC (5%) and xanthan (5%) formulations. From the gums studied, it was concluded that high methoxy HPMC was the optimum hydrocolloid in the rice cassava gluten-free dough. Practical Application Two types of hydrocolloids, xanthan gum and HPMC, were individually added to a gluten-free rice cassava formulation. Based on the thermoanalytic and rheological studies on dough, as well as the bread quality studies, high methoxy HPMC at 5% addition was determined to optimally improve the bread quality when only gum addition was considered. This study indicates the potential use of high methoxy HPMC as an additive in gluten-free bread formulations prior to considering alternative proteins.