Table 3.
Experimental range and values of the independent variables in the central composite design for optimization of extraction conditions
| No. | Independent | Response variables | |||||
|---|---|---|---|---|---|---|---|
| X1 a | X2 | X3 | X4 | Y1 b | Y2 | Y3 | |
| 1 | 30 (-1) | 6 (-1) | 25 (-1) | 12 (-1) | 5.91 | 55.16 | 6.00 |
| 2 | 50 (1) | 6 (-1) | 25 (-1) | 12 (-1) | 3.40 | 32.06 | 7.65 |
| 3 | 30 (-1) | 10 (1) | 25 (-1) | 12 (-1) | 6.55 | 65.20 | 6.00 |
| 4 | 50 (1) | 10 (1) | 25 (-1) | 12 (-1) | 5.47 | 47.47 | 6.70 |
| 5 | 30 (-1) | 6 (-1) | 35 (1) | 12 (-1) | 6.32 | 66.17 | 5.85 |
| 6 | 50 (1) | 6 (-1) | 35 (1) | 12 (-1) | 2.04 | 16.61 | 8.50 |
| 7 | 30 (-1) | 10 (1) | 35 (1) | 12 (-1) | 8.08 | 77.94 | 6.15 |
| 8 | 50 (1) | 10 (1) | 35 (1) | 12 (-1) | 3.70 | 34.71 | 7.30 |
| 9 | 30 (-1) | 6 (-1) | 25 (-1) | 12 (-1) | 4.42 | 41.02 | 6.30 |
| 10 | 50 (1) | 6 (-1) | 25 (-1) | 20 (1) | 6.64 | 67.21 | 7.75 |
| 11 | 30 (-1) | 10 (1) | 25 (-1) | 20 (1) | 6.33 | 63.36 | 6.25 |
| 12 | 50 (1) | 10 (1) | 25 (-1) | 20 (1) | 6.47 | 65.81 | 7.10 |
| 13 | 30 (-1) | 6 (-1) | 35 (1) | 20 (1) | 5.75 | 58.94 | 6.35 |
| 14 | 50 (1) | 6 (-1) | 35 (1) | 20 (1) | 3.62 | 70.81 | 9.25 |
| 15 | 30 (-1) | 10 (1) | 35 (1) | 20 (1) | 6.30 | 64.96 | 6.35 |
| 16 | 50 (1) | 10 (1) | 35 (1) | 20 (1) | 4.67 | 69.92 | 9.00 |
| 17 | 20 (-2) | 8 (0) | 30 (0) | 16 (0) | 3.41 | 20.63 | 5.75 |
| 18 | 60 (2) | 8 (0) | 30 (0) | 16 (0) | 3.80 | 24.07 | 9.10 |
| 19 | 40 (0) | 4 (-2) | 30 (0) | 16 (0) | 4.64 | 40.02 | 5.95 |
| 20 | 40 (0) | 12 (2) | 30 (0) | 16 (0) | 4.63 | 37.48 | 6.00 |
| 21 | 40 (0) | 8 (0) | 20 (-2) | 16 (0) | 6.22 | 52.90 | 6.40 |
| 22 | 40 (0) | 8 (0) | 40 (2) | 16 (0) | 4.92 | 71.46 | 5.75 |
| 23 | 40 (0) | 8 (0) | 30 (0) | 8 (-2) | 6.63 | 60.04 | 2.70 |
| 24 | 40 (0) | 8 (0) | 30 (0) | 24 (+2) | 5.72 | 56.32 | 6.35 |
| 25 | 40 (0) | 8 (0) | 30 (0) | 16 (0) | 4.95 | 45.34 | 5.75 |
| 26 | 40 (0) | 8 (0) | 30 (0) | 16 (0) | 4.34 | 35.13 | 5.78 |
| 27 | 40 (0) | 8 (0) | 30 (0) | 16 (0) | 4.28 | 40.88 | 5.73 |
aX1, extraction temperature (°C); X2, extraction time (hour); X3, solid-liquid ratio (%); X4, solvent volume (1:X)
bY1, total polyphenol content (mg GAE/g); Y2, total anthocyanin content (mg C3GE/100 g) Y3, extraction yield (%)