## 4 Discussion
### Possible Mechanism of PEF Treatment Impact on Starch Digestibility of Oat Flour  
This study clearly shows that the extent of PEF treatment effect on oat flour was dependent on PEF intensity applied (levels of electric field strength and specific energy input). It is noteworthy to mention that with increasing specific energy input application, there is also an inevitable increase in sample temperature during PEF processing, which may be attributed to the electric current that was applied and the dissipation of electric energy to thermal energy within the system. Although the observed increase in temperature during PEF processing is intermittent and short, its influence on the different physicochemical properties of PEF-treated oat flour should not be dismissed. In this context, the synergistic effect of PEF treatment and intermittent temperature increase during oat flour processing is recognised. Based on the findings presented in this study, the potential mechanism of PEF treatment effect on starch digestibility of oat flour is proposed. Figure 7 shows the overview of the impact of PEF treatment, which encompasses both the physical and molecular structures of starch in oat flour. Firstly, PEF treatment of oat flour leads to the observed modification in the physical characteristics of flour components. At certain PEF treatment levels, the surface properties of oat starch are affected. Starch granules with deformed or irregular shapes clump together and produce large clusters of aggregates that resulted in bigger particle size measurement. Secondly, PEF treatment of oat flour affects both the crystalline and amorphous domains of starch in several ways: (1) damage in the starch molecular structure that caused instability in the crystalline region and prompting the conversion of starch crystals to its amorphous form, or (2) the enhanced stability of the crystalline structure, making it denser and more compact. These modifications in the crystalline region further affect the accessibility of starch molecules for possible interactions with other molecules. Any observed change in the molecular structure of starch will impact how it interacts with water, which affects the thermal properties of the sample.  
Starch, being the major component of oat, is the main driver of oat functionality. With the observed changes in the physical and molecular structures of starch, it is expected that oat functionality, such as its susceptibility to digestive enzymes, will also be altered. PEF treatment of oat at 418-484 kJ/kg caused instability in the crystalline structure, which allowed easier access of water to starch molecules and permitted improved facilitation of enzymatic hydrolysis of starch in oat flour. Hence, an increased starch digestibility was observed. On the other hand, the enhanced stability of the crystalline structure in starch appeared to be prohibitive in terms of water access to starch. That is, with PEF treatment, swollen granules of starch will command higher energy requirements to cause the melting of amylopectin crystalline structures and amylose double helices, which leads to increased starch resistance to digestion.  
In addition to starch, the presence of protein (11%), lipids (5%), and \(\beta\)-glucan (1%) in lower amounts and the interaction effects of these macromolecules with starch in oat flour may pose minimal impact on starch digestibility and other related functional characteristics under the influence of PEF. Oat protein may act as a physical barrier to starch digestion [46; 47]. On the other hand, lipids have been reported to limit enzyme hydrolysis by blocking the absorption sites, trapping the starch granules, and promoting the formation of lipid-amylose complex [48; 49]). Lastly, starch hydrolysis may be negatively affected with the presence of \(\beta\)-glucan due to increased viscosity and reduced amylolytic activity [5; 50]. [PERSON] et al. [51] also reported that \(\beta\)-glucan may inhibit enzyme action by encapsulating protein and starch.