# Ohmic Baking of Gluten-Free Bread: Role of Starch and Flour on Batter Properties
## 3 Results and Discussions
### Starch and Flour Properties
B-type starches showed higher peak viscosity, and lower final viscosity than A-type starches (see Table 1). This is in agreement with other studies, which observed that a lower starch swelling power contributed to a decreased starch peak viscosity [20; 21]. High peak viscosity was concomitant with a higher breakdown (\(r=0.99\)). Potato starch had the highest peak viscosity and breakdown, reaching 1105.41 RVU and 953.83 RVU, respectively. The more compact structure of A-type starches leads to higher hot paste stability, e.g., lower breakdown. This behavior suggests that potato starch may have lower resistance during mixing and baking. In contrast, buckwheat flour exhibited the peak viscosity and breakdown, implying stability towards shearing and high temperatures and thus potentially suitable for baking. Another starch property that needs to be considered, specifically in breadmaking, is starch damage. Starch damage represents the structural damage occurring during milling or grinding, which significantly influences the starch behavior. Overall, flours had a higher structural damage than isolated starches, with rice flour being the highest. This is probably explained by the more compact kernels of rice, which may lead to more extensive damage during milling, but also to the type of milling itself, which contributes to the extent of starch damage [22]. Starch damage correlated positively with WHC (\(r=0.93\)) (see Table 2). A damaged starch granule absorbs excessively more water than native starch, as was also seen by [PERSON] et al. [16] for wheat. Additionally, it has been reported that intensive starch damage affects batter handling and bread production negatively. The higher water absorption of damaged granules can lead to the development of sticky dough and may be responsible for a gummy crumb and undesirable bread color [16]. The highest WHC was found in rice flour, which was probably not only related to the amount of damaged starch but also its higher protein content. On the other hand, starch damage showed an inverse relationship with swelling power (\(r=-0.61\)) and solubility index (\(r=-0.62\)). Starch granule rupture decreases starch swelling power of the sample, as the granule is less compact [16; 23]. Apart from the effect of starch damage, swelling power was also influenced by the starch granule size. Flours displayed the largest particle sizes. As protein is concentrated mainly in the outer layers of the kernel and decreases toward the center, the two flours show higher protein content compared to the starches, which influences the overall particle size. Among the starches, corn starch had the smallest and potato starch the coarsest particle size. B-type starches usually have a bigger granule size than the A-type starches, resulting in a higher ability to swell. Yet in this study, wheat starch exhibited a coarser granule size than cassava starch, which might be due to the bimodal granule properties of wheat starch. Granule size was negatively correlated with the pasting temperature, which could be explained by the higher surface area of the smaller granule sizes, leading to increased pasting temperatures. Therefore, B-type starches showed lower pasting temperatures than A-type starches, which apart from their different granule size could also be attributed to their starch granule structure (open/closed packed granule). Rice flour contains particularly small starch granules and thus showed a high pasting temperature. Regarding the retrogradation behavior, setback and final viscosity showed a positive correlation (\(r=0.76\)). Overall, the results showed that the A-type starches had higher final viscosity than B-type starches. [PERSON] & [PERSON] [24] stated that A-type starches tend to retrogradate more easily than B-type starches, leading to high final viscosity. This behavior is also associated with the lower swelling power of A-type than B-type starches.