Table 2.
Actual and coded values of independent variables used for the Central Composite Design and total phenolics content and radical scavenging activity of sweet potato peel extraction trials
| Std Or | Independent variablesa | Results | ||||
|---|---|---|---|---|---|---|
| X1 (mL g−1) | X2 (min) | X3 (°C) | TPC (mg GAE g−1 DM) | ABTS assay (mg TE g−1 DM) | DPPH assay (mg TE g−1 DM) | |
| 1 | 30 (−1) | 30 (−1) | 25 (−1) | 5.77 ± 0.04 | 5.71 ± 0.42 | 20.61 ± 1.28 |
| 2 | 30 (−1) | 30 (−1) | 75 (+1) | 7.89 ± 0.09 | 8.18 ± 0.34 | 19.29 ± 0.43 |
| 3 | 30 (−1) | 90 (+1) | 25 (−1) | 7.01 ± 0.19 | 6.18 ± 0.22 | 21.97 ± 0.75 |
| 4 | 30 (−1) | 90 (+1) | 75 (+1) | 6.09 ± 0.10 | 7.17 ± 0.27 | 23.05 ± 0.35 |
| 5 | 60 (+1) | 30 (−1) | 25 (−1) | 5.72 ± 0.21 | 4.97 ± 0.49 | 31.05 ± 0.59 |
| 6 | 60 (+1) | 30 (−1) | 75 (+1) | 11.35 ± 0.16 | 12.85 ± 0.14 | 45.91 ± 0.52 |
| 7 | 60 (+1) | 90 (+1) | 25 (−1) | 6.51 ± 0.11 | 3.91 ± 0.30 | 37.89 ± 0.70 |
| 8 | 60 (+1) | 90 (+1) | 75 (+1) | 11.11 ± 0.22 | 10.90 ± 0.08 | 45.32 ± 2.13 |
| 9 | 20 (−1.68) | 60 (0) | 50 (0) | 5.64 ± 0.02 | 5.15 ± 0.06 | 13.76 ± 0.33 |
| 10 | 70 (+1.68) | 60 (0) | 50 (0) | 9.36 ± 0.39 | 7.77 ± 0.36 | 49.79 ± 0.69 |
| 11 | 45 (0) | 10 (−1.68) | 50 (0) | 7.08 ± 0.19 | 8.25 ± 0.21 | 30.88 ± 0.98 |
| 12 | 45 (0) | 110 (+1.68) | 50 (0) | 7.24 ± 0.17 | 6.94 ± 0.05 | 31.49 ± 0.17 |
| 13 | 45 (0) | 60 (0) | 8 (−1.68) | 6.47 ± 0.03 | 4.15 ± 0.24 | 31.25 ± 1.57 |
| 14 | 45(0) | 60 (0) | 92 (+1.68) | 11.86 ± 0.29 | 11.94 ± 0.10 | 33.38 ± 2.95 |
| 15 | 45 (0) | 60 (0) | 50 (0) | 8.78 ± 0.25 | 8.06 ± 0.12 | 34.68 ± 0.33 |
| 16 | 45 (0) | 60 (0) | 50 (0) | 8.92 ± 0.75 | 7.87 ± 0.50 | 31.09 ± 0.77 |
| 17 | 45 (0) | 60 (0) | 50 (0) | 8.17 ± 0.17 | 7.97 ± 0.16 | 33.18 ± 0.07 |
| 18 | 45 (0) | 60 (0) | 50 (0) | 8.09 ± 0.20 | 7.66 ± 0.47 | 33.18 ± 1.55 |
| 19 | 45 (0) | 60 (0) | 50 (0) | 7.71 ± 0.24 | 8.00 ± 0.61 | 32.73 ± 1.00 |
| 20 | 45 (0) | 60 (0) | 50 (0) | 8.65 ± 0.11 | 8.39 ± 0.29 | 33.61 ± 1.25 |
Results were expressed as the mean ± SD of three determinations
Std Or standard order, X 1 solvent to solid ratio, X 2 time, X 3 temperature
aCoded values in brackets