# Ohmic Baking of Gluten-Free Bread: Role of Starch and Flour on Batter Properties
## 3 Results and Discussions
### Effect of Batter Rheology on GF Bread Properties  
Table 4 summarizes the effect of starch:water ratio on GF bread properties baked with two different methods, ohmic heating and conventional heating. As expected, ohmic heating showed a positive effect on all GF bread properties compared with conventional heating, except for the baking loss, which was higher in GF bread baked by ohmic heating than by conventional heating. This finding can be explained by the absence of a bread crust in ohmic-heated bread, leading to an increased moisture loss. The water evaporation of this bread occurred more noticeably during storage than during baking itself. Among the starches, ohmic-heated bread made from cassava and potato starch exhibited the lowest baking loss, which could be associated with the higher swelling power of these two starches. In the case of conventional bread, a linear relationship between baking loss and water content of the batter was found, while a non-linear trend was observed for the ohmic-heated bread. A previous investigation suggested that ohmic-heated bread displayed a lower moisture content due to different moisture migration behavior compared to conventionally baked bread [2; 33]. Furthermore, a positive correlation between baking loss and bread volume (\(r=0.67\)) was found. The higher bread volume corresponds to a higher surface area of ohmic-heated bread, resulting in higher water evaporation. The starch:water ratio and thus the apparent viscosity of the batter strongly influenced the bread volume. As mentioned before, the viscosity of GF batter plays an important role in entrapping gas bubbles during mixing and fermentation. According to [PERSON] et al. [8], bread volume was negatively correlated with apparent viscosity and positively correlated with the loss factor \(\tan\delta\) of the dough. An excessive dough viscosity led to a smaller bread volume as the dough could not expand during proofing. In contrast, very low viscosities also led to compact structures, as the dough lost its ability to retain gas, subsequently decreasing the bread volume. In this study, the correlation of apparent viscosity and bread volume was mainly dependent on the characteristics of the starch/flour. The B-type starches produced high bread volume at lower water content and higher apparent viscosity. At the same time, A-type starches demonstrated high bread volume at low and medium water content with lower apparent viscosity than B-type starches. This finding could be associated with the starch properties (breakdown, swelling power, and solubility). As aforementioned, the higher breakdown resulted in lower resistance of the starch granule during mixing, leading to lower bread volume. Additionally, the high swelling power and solubility of potato and cassava starch were responsible for the required low water content to produce high bread volume. The cross-sections of GF bread slices are shown in Figure 2. It can be seen that higher apparent batter viscosities led to an enhanced bread volume for conventionally baked bread. In this case, slow heating led to CO\({}_{2}\) release before the crumb was built; thus, a higher viscosity was needed to trap the CO\({}_{2}\) within the batter system. In contrast, ohmic baking was characterized by uniform and fast heating, resulting in the formation of a stable or firm bread crumb before CO\({}_{2}\) dissipation. The ohmic-heated bread volume was twice as high as the volume of conventionally baked bread (see Table 4). This result demonstrated that adjusting the starch:water ratio of GF batter is an important factor, as it influences the GF batter apparent viscosity, and subsequently its performance in ohmic baking.