## 3 Results and Discussion  
### Effects of Domestic Cooking on Faba Leaf \(\iota\)-dopa Content Variations  
Changes in the \(\iota\)-dopa content of the faba leaves during the domestic cooking treatments are shown in Figure 2. The \(\iota\)-dopa content of the uncooked (0 min) faba leaf of 24.69 mg/g d.w. changed significantly after domestic cooking. After 5 min of microwaving treatment, the \(\iota\)-dopa content increased to 30.51 mg/g d.w. (Figure 2A) but then began to decrease as the cooking time increased. For roasting, there were no significant changes in the \(\iota\)-dopa content after 1 and 5 min (Figure 2B), but a significant decrease to 19.57 mg/g d.w. was observed after 15 min of treatment, to a similar level as that after microwaving for 12 min (21.71 mg/g d.w.). Steaming and boiling are both wet heating methods, but they exhibited different effects on changes in the \(\iota\)-dopa content during processing (Figure 2C,D). The longer steaming treatment (15 min) significantly decreased the \(\iota\)-dopa content (17.53 mg/g d.w.), but it was increased (29.35 mg/g d.w.) by a relatively short cooking time (5 min); however, a boiling treatment of only 1 min maintained the \(\iota\)-dopa content (25.83 mg/g d.w.), but the content decreased significantly as the boiling time increased further. Faba leaves have been reported to be an excellent natural source of \(\iota\)-dopa [4]; however, how to consume \(\iota\)-dopa from faba leaves in one's daily diet is still unclear. The results showed that both microwaving and steaming treatments can efficiently improve the \(\iota\)-dopa content after 5 min of the cooking treatment. Interestingly, even though roasting is also a type of dry heating method, there was no effect on improving the \(\iota\)-dopa content. [PERSON] et al. [22] have investigated the effect of microwave roasting on changes in the physicochemical properties of peanuts, and found that the larger globules of starch and proteins in the peanuts disintegrated as the microwave power and time increased based on SEM. The reason why microwaving increased the \(\iota\)-dopa content could be explained by the fact that that the microwave treatment can help create micropores on the faba leaf, thus accelerating the release of relatively low molecular weight compounds such as  
Figure 2: Changes in \(\iota\)-dopa content of faba leaves with cooking time during: (**A**). microwaving (MW); (**B**). roasting (RT); and (**C**). steaming (SM); and (**D**). boiling (BL). Values are averages with standard errors from triplicate experiments. Different letters on the graph bars indicate a significant difference at \(p<0.05\) ([PERSON]’s HSD test). \(\omega\)-dopa. Microwave energy can also directly penetrate the food matrix, providing faster heating than conventional methods such as roasting, based on surface heating [23]. Our previous results suggested that steaming significantly decreased the \(\iota\)-dopa content of faba leaves after 15 min of treatment [3], which was consistent with the results of the present study; however, the pattern of \(\iota\)-dopa content first increasing then decreasing was shown in faba leaves during steam processing times of up to 15 min (Figure 2C). The longer steaming treatment could have damaged the \(\iota\)-dopa structure, whereas the short-time treatment had increased the extraction efficiency. Of the four domestic cooking methods, the most significant reduction in \(\iota\)-dopa content was observed with the boiling treatment (Figure 2D). Wet heating has been found to cause a stronger deterioration of \(\iota\)-dopa than dry heating.