## 3 Results and Discussion
### Stabilisation Process of Chlorophylls  
#### 3.2.1 Effect of CuSO4 and ZnCl2 Concentrations  
Compared to the chlorophylll content (0.30 mg/g) treated with 60 mg/L of CuSO4, only 0.21 mg/g of total chlorophylll content was achieved by the 300 mg/L of ZnCl2 (Figure 1). Moreover, the greenness (\(-\)a*/b*) of amaranth pures increased with increasing concentrations of both Cu and Zn. For Cu-amaranth pures (Figure 1a), the maximum level of greenness was reached when 210 mg/L of CuSO4 was added. Additionally, no significant (\(p>0.05\)) differences were observed in the greenness values when 210 to 240 mg/L of CuSO4 was added. Thus, the results implied that 210 mg/L of CuSO4 resulted in the complete formation of Cu-chlorophyll derivatives in the amaranth pures.  
In Figure 1a, the chlorophylll derivative contents of the Cu-amaranth pures increased with increasing metal concentrations. Furthermore, no significant (\(p>0.05\)) differences were depicted at 180, 210, and 240 mg/L of CuSO4. Therefore, stabilization at 210 mg/L of CuSO4 was chosen due to its highest greenness value and chlorophylll derivative contents (0.46 mg/g FW). For Zn-amaranth pures (Figure 1b), no significant (\(p>0.05\)) differences were observed when the \(\text{a*/b*}\) value reached its maximum from 1200 to 1800 mg/L of ZnCl2. Meanwhile, chlorophylll derivatives content was significantly highest (0.27 mg/g fresh weight) in Zn-amaranth pure treated with 1500 mg/L of ZnCl2. Hence, 1500 mg/L of ZnCl2 concentration was selected for subsequent experiments. The Zn concentration obtained in this study was close to the finding of [PERSON] et al., which retained the green colour of pears using 1300 mg/L of Zn ions [18]. In this study, the ZnCl2 concentrations were higher than CuSO4 concentrations. Hence, the higher ZnCl2 concentrations were due to Zn salts being less reactive than Cu salts [22; 25]. In addition, the formation of Zn complexes with chlorophylll derivatives occurred much slower than Cu complexes [46]; therefore, more Zn ions are required to form metallo-chlorophyll complexes in amaranth pures.  
Figure 1a,b, demonstrate that the green pigments of the control pures (0 mg/L of Cu or Zn and heated at 80 \({}^{\circ}\)C for 15 min) have mostly degraded. Both control pures turned  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Amaranth with Round Leaves** & **Amaranth with Tapered Leaves** \\ \hline Chlorophyll \(a\) & 28.90 \({}^{\text{b}}\)\(\pm\) 1.47 & 33.54 \({}^{\text{a}}\)\(\pm\) 1.77 \\ Chlorophyll \(b\) & 29.04 \({}^{\text{b}}\)\(\pm\) 1.52 & 34.37 \({}^{\text{a}}\)\(\pm\) 1.93 \\ Total chlorophylll & 57.94 \({}^{\text{b}}\)\(\pm\) 2.99 & 67.91 \({}^{\text{a}}\)\(\pm\) 3.66 \\ \hline \hline \end{tabular} Each value is expressed as mean \(\pm\) standard deviation (\(n=3\)) of triplicate analysis. \({}^{\text{a,b}}\) Means followed by different superscript lowercase letters indicate significant differences (\(p<0.05\)) within a row by [PERSON]’s HSD test.  
\end{table}
Table 1: The chlorophyll content (mg/100 g fresh weight) of green amaranth varieties.  
brownish with a*/b* values of \(-\)0.05 and \(-\)0.04, respectively; therefore, the colour changes could be due to the formation of chlorophyll degradation compounds, which changed from bright green to brownish [47; 48]. In addition, the chlorophyll degradation compounds are Mg-free derivatives, while the control puree had only 0.19 mg/g of total chlorophyll derivative content [49]. Previous studies reported that the formation of metallo-chlorophyll complexes depends on the metal and pigment concentrations, pH [50], temperature [51], and duration of contact between the metal solution and vegetable tissues [22]. Thus, Cu and Zn were used for subsequent studies with concentrations of 210 mg/L and 1500 mg/L, respectively.