Table 1.
Levels and code of variable used for Box–Behnken design (BBD), and the observed responses at different experimental conditions.
| Variable | Units | Symbol | Variable Levels | ||
|---|---|---|---|---|---|
| Low (−1) | Middle (0) | Hight (+1) | |||
| Ethanol concentration | % | X1 | 40 | 60 | 80 |
| Extraction temperature | °C | X2 | 25 | 42.5 | 60 |
| Extraction time | h | X3 | 6 | 15 | 24 |
| Run | Extraction conditions | Experimental results | |||
| X1 (ethanol concentration, %) | X2 (extraction temperature, °C) | X3 (extraction time, h) | TP (mg GAE/g dw) * | TF (mg QE/g dw) * | |
| 1 | 40 (−1) | 42.5 (0) | 24 (+1) | 12.41 | 2.82 |
| 2 | 40 (−1) | 25 (−1) | 15 (0) | 11.59 | 2.75 |
| 3 | 60 (0) | 42.5 (0) | 15 (0) | 15.26 | 2.98 |
| 4 | 60 (0) | 42.5 (0) | 15 (0) | 15.39 | 2.96 |
| 5 | 60 (0) | 60 (+1) | 6 (−1) | 11.57 | 2.73 |
| 6 | 80 (+1) | 60 (+1) | 15 (0) | 13.21 | 2.78 |
| 7 | 60 (0) | 60 (+1) | 24 (+1) | 13.65 | 2.81 |
| 8 | 40 (−1) | 60 (+1) | 15 (0) | 13.67 | 2.84 |
| 9 | 60 (0) | 25 (−1) | 6 (−1) | 12.18 | 2.72 |
| 10 | 80 (+1) | 25 (−1) | 15 (0) | 13.39 | 2.86 |
| 11 | 60 (0) | 42.5 (0) | 15 (0) | 15.26 | 2.98 |
| 12 | 80 (+1) | 42.5 (0) | 6 (−1) | 12.41 | 2.81 |
| 13 | 60 (0) | 25 (−1) | 24 (+1) | 10.31 | 2.77 |
| 14 | 80 (+1) | 42.5 (0) | 24 (+1) | 13.19 | 2.79 |
| 15 | 40 (−1) | 42.5 (0) | 6 (−1) | 12.13 | 2.69 |
* Experiments were performed in triplicate and the data were reported as means of three values.