## 2 Results and Discussion
### Antioxidant Activity and Total Phenolic Content (TPC) Analysis  
The analysis of antioxidant activity and TPC suggests a considerable reduction in radicals of 2.2\({}^{\prime}\)-azinobis(3-ethylbenzothazoline-6-sulfonic acid) (ABTS), and Fe\({}^{+3}\) to Fe\({}^{+2}\) by FRAP methods and TPC values were observed after drying (Table 3). Amongst the drying treatments, the highest antioxidant activity and TPC values were observed for CD at 40 \({}^{\circ}\)C and freeze-dried samples. _C. alata_ dehydrated using CD at 40 \({}^{\circ}\)C achieved higher antioxidant activity in comparison with VMD methods, although the ABTS and FRAP values of CD at 40 \({}^{\circ}\)C was not significantly different than VMD methods (Table 3). This observation could be the result of polyphenols being exposed to oxygenated condition. Polyphenols in an intermediate oxidised state have been reported to show greater antioxidant effect compared with their non-oxidised state [21]. In addition, high-temperature stabilisation process could result in the production of Maillard reaction products (MRPs) formed from Maillard reaction in convective-dried samples. MRPs are known to exhibit antioxidant effect, often by chain breaking mechanism [22]. The assumption that MRPs could contribute to the overall increase in antioxidant activity of CD at 40 \({}^{\circ}\)C samples is supported by the lower \(L^{*}\) values of convective-dried samples compared with VMD samples, which indicates more browning (Table 2). However, only at a low hot-air temperature (40 \({}^{\circ}\)C) was it effective in preserving the antioxidant properties of _C. alata_ because \begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Drying Conditions**} & \multicolumn{3}{c}{**Colour Parameters**} \\ \cline{2-4}  & \(L^{*}\) & \(a^{*}\) & \(b^{*}\) \\ \hline Fresh & \(36.94\pm 0.093\) a & \(-2.75\pm 0.451\) a & \(9.04\pm 0.440\) a \\ FD & \(44.71\pm 0.322\) b & \(-2.17\pm 0.064\) b & \(17.00\pm 0.320\) b \\ CD (40 \({}^{\circ}\)C) & \(38.55\pm 0.095\) b & \(-0.20\pm 0.118\) d,e & \(10.65\pm 0.109\) c \\ CD (50 \({}^{\circ}\)C) & \(38.75\pm 0.070\) b & \(0.00\pm 0.056\) e,f & \(10.53\pm 0.101\) c \\ CD (60 \({}^{\circ}\)C) & \(38.31\pm 0.207\) e & \(0.39\pm 0.025\) g & \(10.04\pm 0.186\) d \\ VMD (6 W/g) & \(40.27\pm 0.036\) d & \(0.45\pm 0.044\) g & \(13.81\pm 0.125\) e \\ VMD (9 W/g) & \(39.42\pm 0.388\) c & \(-0.47\pm 0.051\) c,d & \(11.89\pm 0.143\) f \\ VMD (12 W/g) & \(39.43\pm 0.272\) c & \(-0.54\pm 0.042\) c & \(12.25\pm 0.115\) f \\ CPD-VMFD & \(39.30\pm 0.110\) c & \(0.18\pm 0.055\) f,g & \(11.82\pm 0.149\) f \\ \hline \end{tabular} FD—freeze drying: CD—convective drying: VMD—vacuum microwave drying; CPD—convective pre-drying; VMFD—vacuum microwave finish drying; values with the same letter within a column are not significantly different (\(p<0.05\)), according to [PERSON]’s test.  
\end{table} 
Table 2: Colour parameters \(L^{*}\), \(a^{*}\)_and_\(b^{*}\) of _C. alata_ influenced by different drying methods. the antioxidant activities were seen to decline at 50 \({}^{\circ}\)C and 60 \({}^{\circ}\)C. Samples dried using CD at 60 \({}^{\circ}\)C produced the lowest ABTS, FRAP and TPC values. The high extent of loss in antioxidant values and phenolic content could be attributed to the high degradative temperature at 60 \({}^{\circ}\)C. As for VMD, moderate microwave wattage of 9 W/g was advantageous in achieving high antioxidant effect and TPC. Meanwhile, CPD-VMFD produced intermediate antioxidant activity and TPC values. The TPC values are shown in Table 3. All drying treatments resulted in large reduction in TPC values, with CD at 60 \({}^{\circ}\)C obtaining the lowest TPC value, whilst CD at 40 \({}^{\circ}\)C achieved the highest TPC. Low TPC values of the heat-treated samples may be caused by the oxidative and thermal degradation of phenolic compounds.