## 3 Results and Discussion
### Birefringence of Cassava Starches in HPP-treated Cassava Flours
#### 3.3.3 Thermal Properties of HPP-treated Cassava Flours  
The three-way ANOVA analysis of transitional gelatinization temperatures of cassava flours revealed that only _To_ had a significant three-way interaction effect, and _Tp_ had a two-way interaction effect (Table 2). Hence, _Trange_ had a significant two-way interaction effect. However, no interaction was found for _Tc_. Further analysis on _To_ revealed that there were significant simple simple main effects between pressures across all FC at 10 min HT (all \(p\) < 0.001) and at 20% and 30% FC for 30 min HT (both \(p\) < 0.001). Simple simple comparisons revealed that 600 MPa was consistently higher in _To_ than other pressures in all FC and HT combinations (Figure 6A). Since no endothermic peak was detected at 600-10%-30, it was not included in the analysis. Nevertheless, this indicates full gelatinization of starch in the flour. The significant statistical mean difference between 600 MPa and other pressures decreased progressively with an increase in FC and prolonging HT. Other combinations of simple two-way interactions confirm this observation statistically. The significant two-way interaction of pressure with both FC and HT for _Tp_ revealed a simple main effect result similar to _To_. This suggests that 600 MPa has an increasing effect on _Tp_ regardless of the level of FC and HT, up until complete gelatinization. Despite the increase in both _To_ and _Tp_, the interaction of pressure and HT on _Trange_ revealed that the endothermic peak for gelatinization significantly narrowed by 0.93-1.56 \({}^{\circ}\)C at 600-30 min relative to other pressures and 1.96 \({}^{\circ}\)C narrower than 600-10 min. In the case of _Tc_, only a significant main effect was found, as seen in the similar sharp temperature increase at all 600 MPa treatment combinations. A rising shift in gelatinization temperatures was also observed in HPP-treated chestnut, oat, and quinoa flours [11; 18; 37], indicating the loss of the less stable crystalline structures [33].  
Figure 5: X-ray diffraction spectra of untreated (0.1 MPa) and selected HPP-treated cassava flours; where (**A**) shows spectra for untreated, 300 to 500–10%–10, and 500–10%–30, and (**B**) shows spectra for untreated and all 600 MPa treatment combinations.  
Figure 6: The thermal properties of untreated and HPP-treated cassava flour. (**A**) onset (_Tb_), peak (_Tp_), conclusion, and (_Tc_) gelatinization temperatures; (**B**) temperature range of gelatinization (_Trange_) and gelatinization enthalpy (\(\Delta\)_H_); (**C**) degree of gelatinization. Error bars represent \(\pm\) standard deviation (n = 3).  
The change in gelatinization enthalpy (\(\Delta H\)) and \(DG\) had significant three-way interactions and revealed similar results but inverse values. Both had significant simple two-way interactions between pressure and FC at different levels of HT (all \(p<0.001\)) and a significant simple simple main effect between pressures on all levels of FC and HT (all \(p<0.001\)). The \(\Delta H\) was significantly lower at 600 MPa than other pressures regardless of FC at 10 min HT, while no difference was found between lower pressure combinations (Figure 6B). At 10%-30 min, 500 MPa was significantly higher than 600 MPa, but they were both significantly lower than other pressures. As no endothermic peak was detected at 600-10%-30, it was acknowledged to be fully gelatinized and recorded as 0 J/g or 100% \(DG\). At 20% to 30%-30 min, only 600 MPa was significantly lower than other pressures. These results corroborate with %RC, as enthalpy change associated with gelatinization is measured by DSC and gelatinization involves the disruption of the ordered structure [43]. Consequently, a similar trend was seen in \(DG\) but with increasing values instead (Figure 6C).