Hydrothermal Treatment via Microwave Radiation Improves Viscoelastic Properties of Native Gluten-Free Flours for Extrusion 3D Printing

The market for gluten-free products is experiencing significant growth due to the increase in the number of gluten/wheat affected patients diagnosed, but largely as a result of the emergence of a new niche market dedicated for consumers who optionally avoid gluten. Native flours are perceived as viable alternative for industrially used starch and hydrocolloids blends, mainly due to their lack of vitamins and minerals, which are abundant in non-refined raw materials. Edible inks for on-demand printing are under significant consideration, while texture building capacity remains an issue. As heat-moisture treatment has proved to be useful for stabilizing the pasting and rheological behavior of various native flours, HMT supported by microwave heating was investigated as printable ink stabilizers. For Spanish and Polish buckwheat flours and two different varieties of teff (white and brown) flour pasting, structural and textural characteristics after the microwave supported heat moisture treatment in 30% of initial moisture content were evaluated. The peak viscosity was reduced by 54% and 60% for Polish and Spanish flour, respectively, while for teff, the reduction was 15% and 43% for the white and brown varieties, respectively. Significant improvement in viscoelastic modulus G' (for Polish and Spanish buckwheat flour, 32% and 16%, respectively; for white and brown tef varieties, 14% and 18%, respectively) was observed for all the treated samples regardless of the species or variety; this resulted in better performance during 3D printing.