## 4 Discussion
### Strategies to Improve Gluten-Free Dough Rheology and Bread Characteristics
#### 4.1.3 Improve and Increase Starch Gelatinization and Protein Cross-Linking  
As gluten-free breads are mainly starch matrixes, the gelatinization of starch significantly influences bread quality. Starch gelatinization can only be ensured if enough water is present, and when gelatinized starch is present in the initial stages of breadmaking it can significantly improve dough consistency [13]. Wheat dough development relies on maintaining a low temperature to improve the gluten network [24]; however, non-wheat doughs traditionally rely on blanching, boiling water, and other strategies to induce or increase starch gelatinization. In a novel approach, [PERSON] and [PERSON] (2015) [13] suggested that high hydrostatic pressure could be a way to increase starch gelatinization. Although the strategy was initially developed for gluten breads, results for gluten-free breadmaking are reported to be very promising. The authors found that pressures of 200-600 MPa, particularly above 300 MPa, increased dough consistency due to the pressure-induced gelatinization of starch. The potential use of high pressure (HP) to improve gluten-free doughs and bakery products was confirmed by [PERSON] et al. (2011) [25], who investigated the effects of HP treatments (200, 400, and 600 MPa for 10 min.) on starch gelatinization, protein cross-linking, and rheology, in dough made with buckwheat, rice, and teff flour. With respect to starch gelatinization, starch granules in white rice samples were most sensitive to heat, with gelatinization occurring between 47.7 and 77.9 \({}^{\circ}\)C [25]. Buckwheat starch gelatinized between 50.9 and 81.9 \({}^{\circ}\)C, while teff starch was most resistant to heat, as granule melting started at 54.4 \({}^{\circ}\)C [25]. HP pre-treatment of the batter led to a significant change in the gelatinization temperature. Exposure to 400 MPa for 10 min significantly increased the initial gelatinization temperature in rice and teff samples, while buckwheat also increased, but not significantly [25]. The authors attributed these changes to modifications in the granule structure and crystallinity. The same study of [PERSON] et al. (2011) [25] found that HP treatment increased dough viscosity in all tested samples. For all flours, and all pressures, G' was higher than G\" in the whole range of frequencies. Furthermore, the complex modulus (G*) increased in white rice and buckwheat batters as pressure increased, while the damping factor decreased, indicating the increased contribution of the elastic compound (G') [25]. On the other hand, teff batters responded differently. At pressures up to 200 MPa, the structure weakened, while at >200 MPa it became increasingly elastic and resistant to deformation (higher G*) [25]. The authors suggested that this unusual behavior might be due to the cleavage of disulfide bonds, proteolytic activities, or decreased intrinsic viscosity due to changes in secondary structure [25]. Furthermore, the study used Lab-on-a-Chip capillary gel electrophoresis to reveal protein polymerization by thiol/disulfide-interchange reactions in white rice and teff batters [25]. No such mechanism was observed for buckwheat proteins, which the authors suggested was due to the absence of free sulfhydryl groups [25]. The results presented above were confirmed by [PERSON] et al. (2016) [26], who treated both corn starch and rice flour with HP (600 MPa for 5 min at 40 \({}^{\circ}\)C). In particular, [PERSON] et al. (2016) [26] highlighted a significant increase in water binding capacity that improved dough consistency and workability, despite the higher amount of water required for formation. Moreover, [PERSON] et al. (2016) [26] found that the HP treatment and higher water content resulted in well-leaved breads, characterized by higher specific volume, and good crumb softness. Like [PERSON] et al. (2011) [25], [PERSON] et al. (2016) [26] reported that pressure was consistent with a significant modification in starch functionality, in particular, gel samples had slower hardening kinetics.